Electrical network:

An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, cables, power sources, power sources and switches. An electrical circuit is a network that has a closed loop, which a return path for current. A network is a combination of two or more components, and not necessarily a circuit. Electrical networks that are thrown only by sources (voltage or current), linear elements analyzed in a pot (resistors, capacitors, inductors) and linear distributed elements (lines) by algebraic and transform methods to determine DC response, AC response , and transient response. A network that includes known active electronic components as an electronic circuit. Such networks are nonlinear and usually requires complex design and analysis tools.

Design methods:

To make an electrical circuit, either analog or digital, electrical engineers must be able to predict the voltages and currents at all places within the circuit. Linear circuits, ie circuits with the same input and output frequency can be evaluated by hand, using complex number theory. Other circuits can only be analyzed with special software programs or estimation methods. Circuit simulation software, such as VHDL and HSPICE, the engineers can circuits without the time involved, design, cost and the risk of errors in building circuit prototypes.

Power laws:

A number of electrical laws apply to all electrical networks.

Kirchhoff is the current law:

The sum of all currents into a node is equal to the sum of all currents of the node. Kirchhoff Voltage Law: Be addressed, the sum of the electrical potential differences around a loop must be zero.

Ohm's Law:

The voltage across a resistor is equal to the product of the resistance and the current through them) (at constant temperature.

Norton's theorem:

Any network of voltage and / or current sources and resistors is electrically equivalent to an ideal current source in parallel into a single resistor.

Thévenin's theorem:

Any network of voltage and / or current sources and resistors is electrically equivalent to a voltage source in series with a single resistor. Other, more complex legislation may be needed if the network contains nonlinear or reactive components. Non-linear self-regenerative systems are superimposed aligned. The application of these laws results in a series of equations that can be resolved either by hand or by a computer program.

Network simulation software More complex circuits can be numerically or symbolically using software such as SPICE are analyzed with software such as SAPWin. Linearization at operating point When confronted with a new route, the software first tries to find a steady-state solution, that is, one where all nodes correspond to current law Kirchhoff and the tensions over and through every element of the circuit, the voltage / flow equations for the element.

Once the steady-state solution is found, the operating points of the individual elements in the circuit known. For a small signal analysis, all non-linear element can be linearized around its operating point to reach the small-signal estimate of the voltages and currents. Should an application of Ohm's law. Solve the resulting linear circuit matrix by Gaussian elimination.

Piecewise linear approximation:

PLECS software as the interface to Simulink using piecewise linear approximation of the equations for the elements of a circuit. The circuit is treated as a completely linear network of ideal diodes. Every time a diode switches from A to Off or vice versa, the configuration of the linear network changes. Add more detail to the approximation of equations increases the accuracy of the simulation, but also increases its duration.

Electric Vehicle (EV) Battery Operating Requirements:

For large capacity battery is required to achieve the appropriate category. A typical electric car and driving style depending on the surrounding area uses 150-250 watts mph. Battery deep discharged regularly (80% DOD) operations should be able to The energy content with maximum and deep discharge in full the power is designed to ensure long distance. Potential need for a range of vehicles using different patterns and sizes to satisfy the need.

Should accept too many repetitive pulsed charging currents (5C above) If necessary regenerative braking. Regenerative braking, controlled conditions and low duty rates are possible without charge. (At least desirable-2C). Regularly receives a full charge. Often reaches almost completely discharged. Important to fuel empty "point" gauging. Need a battery management system (BMS). Thermal management is needed. Specific voltage> 300 volts. Typical efficiency> 20-60 kWh. 3 periods and little typical discharge current for durations of peak rate. Because these batteries are physically very large, heavy custom packaging needs and objectives fit the space available in the car.

Similarly, design and layout Pack Weight distribution should be integrated with chassis design for vehicle dynamics so as not disturb. These requirements are particularly important for mechanical passenger cars. Hybrid Electric Vehicle (HEV) Battery Operating Requirements Provides lower engine capacity because the capacity of the battery compared with EVS is important with HEVs can be very small, weight savings. But over time the battery still the same as EV batteries may need to provide immediate energy. This means that small battery should provide more channels when called upon. Battery for a very wide range of the HEV configuration limits as well as adjust the car for performance requirements is necessary.

Some examples: Series hybrid - the engine uses only battery charged. Power system provides a variable speed transmission and electric motor provides total driving force. But the need to reduce capacity requirements EV battery battery charge has a similar engine topped. Parallel hybrid - both engine and electric motor provide power to the wheels. For various configurations to meet different operating conditions is possible. Electric motor taken by the load sharing 100% for zero based on operating conditions and design goals can limit. Battery capacity can be as low as 2 KWh, but it should give the strength of short-term boosts the acceleration and hill climbing for the very high currents will need to 40C.

Design goals that various EV and HEV battery specification are examples of impact: Ability to keep - this engine to run their most efficient constant speed just to keep the battery allows charged. Electric drive and variable power requires finished gearbox offers. This type of campaign was on the first diesel electric locomotives. Better efficiency fuel consumption which in turn automatically reduces exhaust reduces emissions. Efficiency boost - it uses battery power only, which otherwise would be lost to capture the regenerative braking. Captured energy for acceleration and hill climbing power increase is provided.

Limit increase:

It is basically an engine that uses the EV-up battery to prevent discharge of magnitude above the most. Stop / start method - to stop the engine when the vehicle traffic lights or in traffic is established temporarily to save fuel, etc. vehicle under battery power goes off and the engine is restarted when a preset speed until allows access. City and country law - in the city or heavy traffic while the vehicle used in EV mode, where it is most favorable, and a normal internal combustion be used as high speed or long distance highway driving to avoid engine allows the vehicle to limit the boundaries of EV. Multi mode - a combination of versatility in the growth mode can use up.

Capacity and energy:

Than on the operating methods, as various battery performance requirements within an economy will need to adjust, high speed, acceleration, capacity, load limits and take harmful emissions. Battery is an important product differences, that engine is like. Because of the very wide range of needs HEV operating there for a standard battery voltage, battery capacity and power to manage and specifications are intended result of the application class game available exclusively for custom battery must have been designed.

Some specific requirements are as follows: Given to maximum power is made. High power up to 40C (salvation must) accept in repetitive shallow discharging and recharging rates too much. 1000 deep cycle and long life cycle from 400.000 to 1,000,000 cycles shallow. Between 15% and 50% Operating point regenerative braking allow for DOD. Never reaches full discharge. Rarely reaches full charge. Thermal management is needed. Drivers with fuel-gauging and complex equipment required for battery power management BMS regulate. Overall vehicle energy management requirements with interfacing.

Specific voltage> 144 volts.

Typical power> 40 kW (50 bhp).

Capacity, depending on application 1-10 kWh.

As above with EVS, shape, size and weight of battery packs should be consistent with the distribution vehicle. Hybrid Electric Vehicle (PHEV) battery plugs Operating Requirements Batteries for plug in hybrid vehicles should satisfy conflicting performance requirements. In the case of hybrid vehicles generally high power traction batteries for high capacity in terms of pure electric vehicles are optimised for.

EV battery deep depth of discharge (DOD) while the long distance run for HEV down for a long life is on a shallow DOD. Plug in hybrids when charged or over the city and highway driving is to drive for the HEV as being used as both an EV has been created. Dual requirement for a generally increased the power range at a distance of forty miles, as well as lower fees in the state maintaining high power availability (see below), battery very stressful conditions apply. Such as an EV PHEV battery performance is expected both as a HEV.

Requires all large capacity battery electric range, which is called a cost and because the high cost consumers more about the battery life expectations can be satisfied using. Operating Cycle Battery Requirements While cycling is a workhorse in China, are usually 36 volt battery units. Entertainment in the U.S. and Europe, where bicycle more often, lighter, 24 volt battery is used for more popular. For convenient indoor charging module and designed as removable anti-theft as a precaution. 2 hours 5 Amps (based on a 240-360 voltage) for one hour journey to work should be permitted.

Lead acid with high efficiency as possible, says weight is not a limit on portability. Peak Current 15 Amps. 500 cycles or two-year minimum long lifetime. Marine Battery Operating Requirements Deep cycle battery is required. Capabilities and requires such extensive powers. Less weight. Terms are for a wide range of charging should be tolerant. Special environmental conditions. Material handling equipment Battery Operating Requirements Similar for EV applications, but as a common weight restrictions.

Practical traction batteries:

For over a century of lead acid batteries are a major source of energy for traction applications because they are both strong and relatively inexpensive. Fork Lift for Trucks, milk floats and similar applications iron out batteries, which are almost indestructible and has a life of over ten years has also been used successfully. More weight and bulk of these batteries in passenger cars, but their use is precluded.

But out in the 1970s sodium chloride (zebra) designed for traction applications since they are very high energy density batteries that can overcome this problem is likely to offer work started. Unfortunately the battery on the high temperature 270 degrees Celsius are gone and it should have limited his lap. Advent of high power out metal Hydride (NiMH) cells, both of which addressed the problems of weight and operating temperature of many motor vehicle manufacturers or EVS to start HEVs using NiMH batteries is encouraged.

Ambient temperature on NiMH cells. Lead acid cells and a high energy density power cells as the zebra is not as good. Recently, high power lithium ion cell of the high energy density NiMH cells, the same cells with zebra, become available. He also worked at normal temperature and just being introduced in the new electric vehicle design. These new high-energy cells but are more vulnerable to abuse and battery management systems, electronic support and the need to provide protection to ensure long life cycle.

Traction Battery Chargers:

High power high efficiency battery charging time to obtain appropriate chargers and should be compatible with the chemistry and cell chargers are able to interface with cell protection circuitry is essential. Just as a car battery to match, are custom designs and battery charger must match. More information can be found in the section on Chargers.

UPS: Inverters provide control alternating current (AC):

supply of a DC or AC source.

There are two broad classes of applications:
Providing a fixed output from a variable source UPS designed to provide regulated supply lines from sources that may have a variable input voltage (AC or DC) or if the electricity network, an input variable frequency. These applications include May standby generators, power supplies (UPS) or distributed power generation from wind and other intermittent resources. All must issue a fixed output voltage and frequency to the load since the applications expect and depend on it in May.
Providing a variable flow from a stationary source Moreover, many applications require inverters to accept a fixed voltage and frequency AC voltage area and provide a different voltage or variable frequency for applications such as control of motor speed. .
In both models, a bridge rectifier is used to provide power through DC with a current link "to a standard AC inverter.
The circuit below shows the principle of such an inverter designed for three phase applications.
Three frequency inverter variable phase
The third phase sinusoidal input is sent to a simple diode full wave bridge rectifier block issuing a fixed voltage to the UPS. The connection between the rectifier and the inverter is known as the current link. The transistors are switched inverter in the sequence of numbers as shown in the diagram with a time difference if T / 6 and each transistor is kept for a period of T / 4, where T is the period of time for each complete cycle. Line output waveform voltage of each phase is presented below.
This reference frequency converter may simply be a voltage applied to the input of a Voltage Controlled Oscillator (VCO), examples of which are usually available as integrated circuit chips, or it may be derived from a microprocessor clock. Digital logic circuits are used to obtain trigger pulses programmed to the UPS source of reference frequency. In the case of generators supplying AC power, the value of the reference frequency will be set.
The amplitude of the output waveform is determined by the voltage level DC power inverter block but can be modified by thyristor (SCR) control of the rectifier circuit to provide variable voltage to the current link .
Instead of transistor switches, the inverter May use MOSFET, IGBT or CSIS.
Free-wheeling diodes connected to the terminals of the transistors to protect them against wave reverse bias due to inductive motor rot on the ground that occurs when the transistors turn up freewheeling paths for stored energy.
The waveforms for applications such as traction is often reinforced waves rather than pure sine waves because they are easier to produce and engine smooth waves.
Variable frequency drives are used when the variable speed control is required. The wave frequency is controlled by a variable frequency clock which triggers impulses.
For speed control in machines ac voltage and frequency must vary in unison. See AC speed control motor. In open loop systems the operating point is set by a speed reference and speed of equilibrium is determined by the load torque. A closed loop system allows a fixed speed to define. This requires a tachometer to provide feedback of the actual speed comparison with the desired speed. If there is a difference, an error signal is generated to bring the actual speed in accordance with the reference speed by adjusting both the voltage and frequency to eliminate the speed difference.
Volts / Hertz Control Volts / Hertz control is required to control the speed of induction motors. In a system open loop control system converts the desired speed to a reference input frequency to a variable frequency, variable voltage inverter. At the same time, it multiplies the reference frequency by the Volts / Hertz characteristic ratio of the engine to provide the reference voltage corresponding to the UPS. Change the reference speed will then cause the voltage and frequency output of the inverter to change in unison.
In a closed loop system response to the treatment provided from a tachometer signal on the output shaft of the engine is used in the control loop to derive an error signal speed to drive a Volts / Hertz function control similar to that described above.
As for large DC motors, cruise control is normally accompanied by current control.
Cycloconverter:
The Cycloconverter converts AC supply frequency directly to an AC variable frequency without the stage of the DC intermediate link.
The system is complex and operates by sampling the voltage of each phase of AC power and synthesize the desired output signal by switching on the responsibility for the duration of the sampling period, the phase whose voltage is closer to the desired voltage at the instant of sampling. The waveform output is severely distorted and the ability of induction motors to deal with the harmonic content of extra high frequencies within which the system can be used.
Cycloconverters only suitable for very low frequencies up to 30% of the input frequency. They are used for drives at low speed high power to eliminate the need for a gearbox in heavy rolling and crushing plant and the uses pulling trains and ships.
Vector Control - RSS or field oriented control (FOC) All engines require a magnetizing current and torque producing current. In a dc motor brushed, these two trends are connected to two different windings. The magnetizing current is supplied to the stator or field coil and torque producing current is fed into the rotor winding. This allows independent control of both the stator and rotor fields. However in motors such as brushless permanent magnet or induction motors, it is not possible to control the rotor field directly because there are no connections to it. Because the parameters to be checked can not be measured, their value is derived from parameters that can be measured and monitored. Admission only on which control is possible is the input current supplied to the stator.
The stator current interest is the vector sum of two current vectors, induction (delayed phase) vector magnetizing current produces the flux in the gap and in phase, producing a torque, power. To change the torque we need change in phase, producing a torque, current, but because we want the gap airflow remains constant at its optimum level, the magnetizing current should also remain unchanged at change of torque.
Vector control or field-oriented control is a more or less independently of the magnitude and phase of the stator current vectors to adapt to the instantaneous speed and torque applications on the engine.
It allows the parameters on which no direct control can be changed by changing the position, parameters which can be measured and monitored.
To control many applications vector is not necessary, but control precision and maximum efficiency and rapid response, control field of the rotor is necessary and other methods of indirect control were developed. Given the low cost of computing power, vector control is used in automotive applications increasingly brushless.
Vector Control Summary Objectives Maximum current-torque power conversion, fast transient response, precise control of torque, speed and position. Rotating flux need to be maintained at 90 degrees to the flow of the rotor. Inputs of information (state voltages and currents of the stator and the rotor position and / or speed). Uses two independent control loops for control of the magnetization and torque producing current vectors. Calculates mathematical error transforms to analyze the input signals of the stator and calculate any deviation from the desired conditions of the rotor. Calculates correct mathematical inverse transform to convert the error signal rear rotor command signals applied to the stator to counter the error. Active pulse width modulated (PWM) inverter supplying power to the engine.

Stator produces waveforms of input voltage correct amplitude, frequency and phase for the change. Method 1 Direct Control position sensors and uses complex mathematical transforms Method 2 indirect control "sensorless" Use more complex mathematical transforms (Both methods above use current sensors for monitoring current stator windings) Control signals status Samples repeats and provides 20 kHz for ongoing monitoring. Additional benefits low speed control, improved efficiency, smaller engines.
The good news is that detailed knowledge of the process involved is not necessary since most of these tasks are performed in integrated circuits and incorporated into the design of the engine. But read on to find out how the overall system is used.
Transient Response Despite its many advantages, the venerable induction motor is relatively slow to react to changing load conditions or user commands to change speed. This is mainly because the current rotor can not follow instantaneously the applied voltage due to the delay caused by the inductance of the motor windings.
During the transition period the amplitude of the flux and its angle relative to the rotor must be maintained so that the desired torque can be developed.
Torque also depends on the importance of the flow, but it depends on the inductive current component and can be changed instantly. In any case, the flux density is set to its optimum point before saturation occurs.
Vector control is a way to change the current vector in phase without changing the magnetization vector inductive current so that the response time of the machine is not subject to delay induction.

Efficiency:

The inductive phase shift noted above also results in an immediate loss of torque and the low efficiency because of the torque producing stator flux is not acting 90 degrees to the electric field of the rotor.
Torque on the rotor of a motor at its maximum when the magnetic field due to the rotor is perpendicular to the field due to the stator. View Interactive Fields
The system of vector control provides instant adjustments stator currents to control the rotor position relative to the wave of displaced flow thereby avoiding losses due to the lag phase.
Implementation Both control methods described below describe each processing a sample of engine condition and how the error correction occurs. They both involve a lot of processing power of mathematics. The engine requires however continuous real time control to regulate the speed and torque and it takes sampling rate of 20 kHz or more to increase the processing load of the signal dramatically. This task is well within the scope of digital signal processors (DSP) integrated circuits designed for special applications of supercomputing.
Once the engine has a computer on board other functions such as communications and network (CAN bus) can be integrated with the motor controllers.
The system of vector control is essentially an indirect system using information on the system gain knowledge of voltages and currents of the stator and position. Both the "direct" and "indirect" methods of checks to indicate below the details of the rotor position is obtained.
For further information about stator currents in a three phase system, it suffices to measure two of the three phase currents supplied to the engine because the sum of the currents flowing in two windings must equal the course of the third winding.
Direct control:

This method uses a position sensor to determine the angular position of the rotating shaft. The angle between the rotor flux and the wave rotating flux is the sum of the angular position of the shaft and drift angle can be derived from the rotor current. The position error (difference of 90 degrees) is able to produce the necessary torque component of stator current. This signal can then be used as a basis for a classical loop current control.
The component of current flow in the stator must be calculated using a mathematical model of the engine. A mathematical transformation (Clarke-Park transformation) is performed on the actual stator currents to derive a measure of actual flow and a representation of the deviation from the desired value. The inverse transform is used to derive the correction signals corresponding error to be applied to the input of a frequency variable to generate appropriate stator current (amplitude, frequency and phase) to correct the error.
The mathematical processes require specific inputs on the mechanical and electrical machine which are often difficult to measure or estimate. Self-learning adaptive control systems have come to the rescue to generate baseline data from measurements of actual performance.
Control algorithms must also take account of environmental conditions. For example, the motor winding resistance (and therefore the L / R time constant of the engine) depends on the temperature and the effect of temperature changes to be incorporated into the model.
Indirect - Sensorless Control Sensorless control refers only to the elimination of the position of the detector used in the diagram above. The control system may have several other sensors. The position information provided by the position sensor can also be derived from mathematical transformations on stator currents and voltages along the stream is in the direct system. Since the physical sensor adds to the complexity and cost of the machine, and the cost of computing power is continually reduced, the replacement of the sensor by mathematical techniques is now economically justified.
The method of sensorless control can be used to control the motor speed to near zero.
Actuators Many of the techniques involved in vector control applicable to systems of oppression and therefore controlled vector system are the replacement of some traditional servo systems.

Ward Leonard Controller:

The Ward Leonard speed controller allows for variable speed drive of the fixed voltage and frequency of AC mains power. It uses three machines, induction motor ac driven at a fixed speed AC power, driving a DC generator which in turn is a dc motor shunt wound, generally of similar construction to generator. The generator output current is directly connected to the armature of the DC motor. The motor speed is adjusted using a rheostat to adjust the excitation current in the winding of the generator to vary the output voltage of the generator. Ward Leonard controllers can still see in lifts (elevators) throughout the world as well as electric cranes, winding gear coal mine machinery and industrial processes, although they were largely replaced by auditors thyristor speed.
Position Control Stepper motors:

It is generally used when the precise position control is necessary. Precise positioning is possible with an open-loop system by counting pulses applied to the motor. Potentiometers can be used to provide position feedback in closed loop systems, but shaft encoders provide more detailed comments Travel counting pulses.
When long distances to the target or engine revolutions many are involved, it may be desirable to accelerate the engine during the trip. In this case speed control may be provided by a feedback loop.
Electronic switching:

The function of the switch is to change the direction of the motor excitation current as the rotor poles pass the alternative poles of the stator. In brushless DC motors, the mechanical switch is eliminated and the current remote power is supplied by the stator coils. Switching is performed by electronic switches which reverse the stator current as the rotor poles alternate through the poles of the stator. This requires a position sensor feedback from the angular position of the rotor controller engine to enable them to change the direction of current when the rotor poles are in the correct position relative to the poles of the stator.
From Some engine models are not independent start when power is applied. These problems are usually treated by the manufacturer of machines using auxiliary windings or other methods and are usually not visible to the user.
One problem encountered by the user is only from many machines, comes with a high inrush current which is potentially damaging to the engine or food. Current control systems described above are used to overcome this problem.
Regenerative Braking:

The battery can capture energy from regenerative braking when maximum volts regen exceed the volt battery. With a DC motor, DC needs a variable - DC converter whose output is based on engine speed to convert the pulses of high voltage low at low speed braking high voltage low current pulses . The control system must also withdraw any voltage regen that exceeds the burden of high-voltage battery to avoid damaging the battery and it must dump excess energy into a resistive load when the battery reaches its full state of charge (SOC) of 100% or the current reaches the battery recommended charge current limit. This is particularly important for lithium batteries.
To capture energy from regenerative braking induction motors synchronous speed required to be reduced below the engine speed by reducing the frequency of supply. See generator action.
Power Factor:

Correction To avoid unnecessary losses, or to meet the load requirements acceptable to the utility of energy supply, correcting the power factor is often needed for induction motors, particularly for large machines or in facilities being implementing many machines.
The most common factor correction power is through capacitors added, however, under certain conditions, the motor controller can also be used for this purpose
In low load conditions the magnetization current in an induction motor is relatively high compared to the current load causing low power factor. (See Induction Motors). Because the charge is increased, the load increases in the current phase with respect to the magnetizing current, thus improving (increasing) the power factor.
The motor controller can be used to treat the problem of low power factor in lightly loaded machines. If the voltage is reduced to levels of light load, the airflow gap will be reduced accordingly and the current (and sliding) must increase to produce the same torque. The effect is to increase the charge current with respect to the magnetizing current, reducing the current weakness and increasing the power factor. Thyristor simple control of the supply voltage is sufficient to provide the control voltage necessary to implement this plan.
The control method of power factor is only practical for lightly loaded machines. Heavily loaded with power factor of the machinery is normally quite high and the effect of control voltage is not significant.
Protection Control systems described above are also designed to ensure that the electrical machine does not exceed its voltage and current. In addition, the machine in May incorporate several protection devices simple.
When overheated, a temperature sensor or thermistor causes power to be switched off or cooling systems to be turned on. If it exceeds a speed limit of safety, a centrifugal switch interrupting the current.
Sensors:

Examples of many types of sensors used in electronic engine control are given below.
Current -- Current Shunt - economic risk of loss. Current Transformer - Efficient, AC only - can not measure DC. Hall effect sensor. Voltage - A to D converters Frequency - pulse counting. Phase - derivative time difference between measured and reference sources. Temperature - thermistors, thermocouples. Light - opto-electronic and optical fibers. Magnetic flux - Hall effect sensor. Position - linear and angular. Optical encoders (based on a light source, a code wheel and an optical detector). Pulse counters - Linear and angular displacements. Pulses may be magnetic or optical. Potentiometers - Limited range, low accuracy. Speed - Tachometer based on different principles. Rotary DC generator - Provides a voltage output. Pulse counters - Legumes may be magnetic or optical. Centrifugal switch (limit switch). Torque - usually from motor current. Time - Microprocessor clock.
Practice Controllers Simple and low cost, low-power machines are usually open systems simple loop. Commons brushed DC motor, for example, needs only one simple voltage controller to control speed, low cost, integrated circuit controllers are available for this purpose. Machines with higher power, however, tend to use closed-loop controllers more complex are generally tailored to each particular machine, often incorporated into the machine itself. Electronic circuits in the motor controller must be able to handle the maximum engine power and this may be a limiting factor in designing a train driving.

The main variable influencing the peak power current, because it defines the cost of power electronics for a maximum voltage given. It is often necessary to use liquid cooling to accommodate high power levels required by the engine.
Polyphase machines need a set of circuits of power and control phase. The cost of the controller often limits the number of motor phases practices typically 3 or 4. Safety features also play a greater role in larger machines because in case of machine failure the damage potential is greater. Inverters, converters and collector circuits used in motor controllers needles all very high currents are therefore likely to be a source of radio interference (RFI).

The system designer must also be aware of the consequences of high frequency current high loads pulsed inverters and choppers May have on battery life in systems of dc traction, such as hybrid electric vehicles. Similarly, the regulated voltage generator on the board and the regenerative braking pulse of charge can also impair the battery if left unchecked.

Generators:

Include Which essentially includes a synchronous generators include motors connected to the supply frequency above the running speed. They have no use producing or stressful stimulation until they are connected to an external source. Squirrel cage used for building small-scale power generation because it is, simple is strong and production is cheaper.
Fixed speed induction generator:

In fact a small speed generators include fixed speed generator connected with slip on the border runs. They receive power supply grid, and their excitement is only in parallel with the supply may run. When the line was, he grid, where they present their excitement but as an additional generator is useless when the power grid goes down right to return power to take. Restricted their limited speed limit possible applications.
Variable speed - self excited induction generator SEIG ():

Small-scale power generation systems are often stand alone applications, from grid power supply, wind and water power widely used as a source of energy for their unstable energy sources. Fixed speed is not suitable for applications that include the generator. Some form of self stimulation generators include variable speed is required as well as to optimize the power of their irregular voltage and frequency output are able to use practical.
Operation:

Self excitation of the generator is obtained by adding capacitors across the stator terminals. When an external prime mover, a small residual magnetism in the rotor due to current flow will be induced in the stator coils as driven by the existing duty reduction windings and capacitors. As the rotor turns, stator windings cutting the opposite direction of change as the remains of the magnetic field orientation changes with rotor will flow. In this case the current will be induced in the opposite direction will make the discharge capacitors. But at the same time machine to release the capacitors charge current increase will flow are strong. As the rotor and stator windings current turn to EMF induced growth will continue until steady state is attained in progress, machine, depending on the magnetic circuit saturation.

Voltage and current for the time this work was determined by peak value and frequency characteristics of the machine will continue to oscillate, in the air gap, slip, weight and capacitor size options. A combination of these factors than speed limit on the maximum and minimum limits set is self stimulation. Is usually small and the operating slip frequency limit depends on the speed of change operations.
If the generator voltage one way to make itself overloaded decline rapidly - will provide security.
Control Include one variable speed drive applications for generators need a converter or power supply grid determine the frequency of the variable frequency generator production optimization. During operation the controllable factors include a self-excited generator mechanical input from the prime mover is available in the affected production, so the system response is not responsible for effective control. Necessary to issue a controllable voltage and frequency, external AC / DC / AC converters are provided. A three-phase diode bridge three phase generator output voltage and frequency required for the thyristor inverter converts DC power from a DC link to provide the link current is used to correct.

DC generators Dynamos () Direct current (DC) Generator:
Stable region for AC generator can be modified as described above is one communicator with an appropriate current Unidirectional slip rings on the rotor shaft as a conductor to replace Horoscope by each half cycle to reverse connections north and south magnetic Optional pole passes. But now the tide of current as the one shown below rectifier as one half of the waveform will be a series of sinusoidal pulses.
Output voltage ripple can be reduced by using a multipole design.
Construction of a DC generator is similar to the construction of a DC motor.
Providing a sector electromagnet are of rotor excitation. Present in very large generators with rotor or stator case derived from a different rotation on the rotor shaft is provocative. The connection is through a commutator rotor, stator windings so that the direction of current in the direction of change as rotor poles alternate between north and south poles pass through the stator. Currently very low rotor current and stator windings is busy in summer's most heavily stator structure is compared with.

In self-excited machines, when starting from rest, currently working up electromagnets and the magnetic circuit around the small residual magnetism present in the electromagnets is drawn from.

Automotive Alternators A variable speed DC generator automotive production levels to a certain machine is AC.

Generators are typically excited turn on a machine. Instead of using an alternator by a DC one and its potential reliability problems can be avoided commutator generator use. However, current direct and addition is required to load in the car, including batteries, DC output voltage regardless of engine speed or load current must be constant. So one rectifier for charging system and a regulator designed to convert AC to DC engine speed to maintain the voltage generated within the limits will include independent.
Rotor is driven by engine and provides field excitation. Its speed is directly related to engine speed and the drive ratio gearing or pulleys depends. Stator is taken from current production.
Generally, a three phase alternators automotive machines compact design at the same time spread between the windings by three sets of stator windings and are able to reduce the present. This improvement gives the possible decrease in voltage ripple.

Construction A claw pole rotor and a rotor, which rotor electromagnet in the south of the North form two ends of poles. 'Claws' of each other effectively as a productive alternative north and south poles of the stator poles will spend between. Rotor with three auxiliary diode current active electromagnet stator windings is fed through which to improve it through two slip rings before a rotor passing through wire.
To move an existing magnetic field rotor poles associated with the stator windings as the current flows in the region over the stator conductors.
A complete three phase current wave of reform generated by alternator, the diode bridge circuit is a DC output yield. Engine alternator Alternator EMF directly (or is proportional to) the speed. But all is designed Alternator voltage, common as a 12 volt nominal 14.2 volts for lead acid batteries, and engine idle speed as the speed increases to maintain the level of the output voltage constant.

Voltage regulator DC output voltage to prevent battery from being overcharged for a maximum 14.2 volts to charge the battery should be kept below the specified voltage. The regulator's job is that if it senses alternator output voltage exceeds 14.2 volts reference voltage is provided by a Zener diode, the field (rotor) is in between the existing curve. Voltage drop of a region without current alternator begins. Falls below the reference voltage when the alternator voltage, current field once again at the desired level of output voltage to be supplied to maintain the wire.

This type of engine rotor speed limit receive a pulsed DC current to operate, install something by closing Rotor smoothed. Alternative design and a feedback current alternator load using pulse width modulation to provide a constant output voltage regardless of load control system provides monitoring of stator current.

Electric Drives:

Motor Controllers and Control Systems (Description and Applications):
Purpose For many years the controller engine was a box which provides control of engine speed and allowed the engine to adapt to variations in load. Projects were often at a loss or provided only slow increases in the control of parameters.
Modern controllers can integrate both power electronics and microprocessors, allowing the check to take on many more tasks and apply them more accurately. These tasks include:
Monitoring the dynamics of the machine and its response to applied loads. (speed, torque and efficiency of the machine or the position of the moving parts.) Providing electronic conversion. Turn yourself starting the engine. The protection of the engine and the controller itself from harm or abuse. Matching the power sources available to meet the engine requirements (voltage, frequency, number of phases).

This is an example of "Power Conditioning" whose purpose is to provide pure sinewave power DC or without harmonics or interference. Although it could be an integral part of the generator control system in general, conditioning could also be provided by a separate autonomous unit operating on any energy source.
Control System Principles:

Open Loop Systems (manual control) In an open loop control system are the control parameters specified or operator and the system finds its own equilibrium.

In the case of an engine balance desired function may be the motor speed or angular position. The controlling parameters such as the supply voltage or load may or may not be under the control of the operator.
If any of the parameters such as load or supply voltage changed the engine will find a new equilibrium, in this case will settle at different speeds. The true equilibrium can be changed by forcing a change in parameters on which the operator has control.

Closed Loop Systems (Automatic Control):

Just set the initial operating parameters, an open loop system can not respond to subsequent changes or disturbances in the system operating environment such as temperature and pressure, or different requirements for the system, such as power supply or load conditions.
For monitoring and control mode of a system without operator intervention, for greater accuracy and faster response, require automatic control.
Negative feedback
To meet these requirements "closed loop" systems are needed. Also called the control feedback or negative feedback, allowing the user to specify a desired running object or reference and control system will automatically move the system to the desired operating point and maintain it at this point then.
A sensor used to monitor the effective running of the system and feed back to the input of the controller analog or digital signal representing the state exit. The actual and desired or reference than ever if the reality is different from the baseline, an error message is created that the auditor uses to force the change of parameters checked to eliminate errors in driving the system back in the desired operating point.
Gain Loop:

The error signal is usually very small so the control circuit or mechanism must include a high gain "amp error" to provide the controlling signal with the power to influence change.
The aid provided for in the loop called the loop gain.
Loop Delay:

The answer is not always instantaneous as there is usually a delay between sensing the error, or targeted at a new location, and correcting errors or moving in the desired new location. This delay is called delay loop.
In mechanical systems the delay may be due to the inertia associated with the lowest possible speed to get a large mass to move when a force is applied.
Electrical circuits the delay may be associated with the inductive circuit elements that may reduce the rate of current build up in the circuit when the voltage is applied.

The closed loop control systems should act quickly to implement error correction without delay before the system has time to change to a different situation. Otherwise, the system may become unstable.
When there is a time lag between sensing the error and completion of remedial measures and the loop gain is large enough system the system can be exceeded. If this occurs, the error will then be in the opposite direction and control system will be reversed also the direction of action to fix this new error. The result is that the actual position will vary around the desired position. This instability is called hunting, and the system hunts to find the point of view.
At worst, the slow reaction to correct the error will reach 180 degrees outside stage with the disorder try to eleiminate. When this occurs, the direction of the system response will not act to eliminate the error, instead will increase the error. Thus, the delay has changed the system's response to negative feedback to positive feedback and the system is critically unstable.

If the loop gain is ot greater unity in the frequency of an input sinusoid if the delay time the system is equal to half the period of the cycle, the sytem will be unstable.
In practical terms, a system with high electrical or mechanical inertia will have a slow response (long delay). With a small, correcting errors of action (mechanical power or voltage), the system will slow in responding (acceleration), but because they are slow, will also have a little momentum and will tend to settle to the desired operating point when the error correcting power is removed.
The delay in implementation of corrective measures, but depends on the loop gain.
If, on the same system, the error correcting power is high (amplified / higher gain loop), as in a fast-acting, the system will respond (alert) faster (less delay), but has higher sprint (faster response). When the error correcting power is removed, and any system of high inertia, momentum of the system will keep moving and it will overshoot the target position. Applying the error message in the opposite direction to bring the system back in order, will cause it to excess in the opposite direction.
Nyquist shows how delay can be tolerated in a system with unity gain loop, and determining the point at which the system becomes unstable
In the example of a DC electric motor, the desired mode can be a particular speed. A tachometer is used to measure the actual speed in comparison with the reference speed. If different, an error message, the size and polarity of which corresponds to the difference between the reference and actual speed, is supplied with a voltage controller to change the engine speed to reduce the error message. With the engine at the desired speed signal error is zero and the engine will maintain the speed.
The three different types of treatment commonly used in error control, P, I and D, named after three main ways to manipulate the error information. Analog - Analog error correction multiplies the error of a (negative) constant P, and adds that the controlled quantity. Integral - Integral error correction incorporates past experience. Integrates the error over a period and then multiply by a (negative) constant I and adds that the controlled quantity. Balance is based on the average error and avoid excess vibration and a more stable system. - Production debugging based on the rate of change of error and reflect future expectations. Used in so-called "Predictive Controllers". The first derivative of the error over time is calculated and multiplied by another (negative) constant D, and also added the controlled quantity.

The derivative term provides a quick response to the climate system. The combinations of three treatments of error are often used simultaneously "PID" Those responsible for dealing with different priorities of system performance. Where noise can be a problem, the derivative term is not used.
Four Quadrant Operation When an electric motor is required to work as both an engine and generator, both forward and reverse directions is said to be four quadrant operation. A simple engine operates only in one direction and never driven a generator is an example of a single application quadrant. An engine designed for automotive use which must run forward and reverse directions, which should provide regenerative braking in both directions, the needs of four quadrant controller.
Control systems for four quadrant applications will obviously be more complex than single quadrant of the controls.

Basic Motor Control functions and applications Auditors may have some or all of the following functions many of which have been applied to integrated circuits.

Speed DC machines One of the main attractions of brushed DC motors is the simplicity of the controls. The speed is proportional to the voltage and the torque is proportional to the current.
Speed control used in brushed DC motors to be achieved by varying the voltage supply, using lossy rheostats in voltage. The speed shunt wound DC motors can be controlled through the weakened area. Today electronic control voltage is employed. See below.
Simple open-loop voltage control is adequate when the engine has a fixed load, however, open loop voltage control can not respond to changes in load on the engine. If the load, engine speed will change. If the load increases, the engine has to deliver more torque to reach an equilibrium position and it needs more power. The engine slows down accordingly, reducing the back EMF, so that more current flows.

To maintain the desired speed, the voltage change is necessary to provide the necessary current required by the new load conditions. Automatic speed control can be achieved only in a closed loop. This uses a tachogenerator on the output shaft to a feedback measure the actual speed. When this is compared with the desired speed, a "velocity error" signal is produced which is used to change the input voltage to the motor lead to the desired speed. Note - This is essentially a system voltage control since the tachogenerator usually provides a dc output that is compared with an input voltage reference.
Voltage control alone may be insufficient to cover the broad, rapidly changing load on the engine after the voltage controller may request currents in excess of the limits of the design of motors. A separate current feedback loop may be required to provide automatic current control. The current control loop must be nested within the voltage control loop. This allows the voltage control loop to provide more modern, but can not override the current control which ensures that the current stays within the limits set by the current control loop.
The Brushless DC motor powered by a pulsed DC supply create a rotating field and the speed is synchronous with the frequency of rotating field. Speed is controlled by varying the frequency of supply. Inverters see below.
AC machines The speed of AC depends generally on the frequency of the voltage supply and the number of magnetic poles per phase in stator. Early speed controllers depends on the transition to a different number of poles and control was only available with manual and slow steps. Modern electronic converters make continuously variable frequency supply may enable closed-loop speed control. To control the speed induction motors, but the supply voltage must change in harmony with the frequency. This requires a special Volts / Hertz control.
Torque Control If the application requires direct control of torque rather than speed, in simple machines can be achieved by controlling the flow, which is proportional to torque, and omitting the loop speed control. For more precise control, the auditors used the disease entities.

Voltage Control It is no longer necessary to use energy wasting rheostats to provide a variable voltage.

Voltage Choppers Modern controllers use switching regulators or channels helicopter to provide a variable DC voltage supply from a fixed DC. The dc power supply is switched on and off at high frequency (typically 10 kHz or more) with the use of electronic switching devices such as MOSFETs, IGBTs or GTOS providing wave form of pulsed DC. The average output current can be controlled by changing the duty cycle of the helicopter.

Pulse Width Modulation (PWM):

AC voltages can be controlled in the same way bi-directional pulses to represent the sine wave.
The PID controller are also called "3 term controllers:

Motor controllers can be simple or open loop systems may include various inserts closed loop systems operating simultaneously. For example, closed-loop controls can be used to synchronize the excitation of stator poles in the angular position of the cursor or simply to control the motor speed or angular position of the cursor.

Pulse Frequency Modulation - PFM
Various PWM schemes are possible. Only one is shown here. By varying the pulse width of the amplitude of the sine wave can be changed.
Variable voltage can be generated through the use of fixed pulse width, but instead (by different pulse amplitude (pulse amplitude modulation - PAM) or pulse rate Pulse Frequency Modulation - PFM).
The DC output from Chopper and PWM circuits is known to be plagued by high harmonic content. Most DC motors, but can tolerate a pulsed DC supply, since the inductance of the motor itself and the mechanical inertia of the rotor to help smooth out the fluctuations in the supply voltage. Since there is no current when the switching device is switched off, the technique is relatively lossless. Cogging can occur if the chopper frequency is too low.
The voltage regulator can be manually activated in an open-loop system, but for the continuous voltage control, the inverter must be included in a feedback loop in a closed-loop system. The control system monitors the actual output voltage and provides a control signal, which is an analog or a digital representation of the error signal to correct the pulse width modulator of any discrepancies. If voltage is control for controlling the speed of the error signal is a tachometer generator to the engine output shaft will be used derived.
Electronic voltage regulation is also an essential part of many generator applications. In automotive systems, generator or alternator with variable speed, which depends directly driven by the engine speed. It has its full voltage at the output of the lowest speed to give, but the tension is when the engine speed increases will be retained. Generators used in 12 volt systems usually have built in voltage regulation. In HEV applications a chopper regulator at the output of the generator used to keep the voltage on the DC-link within narrow limits in order to damage the battery. If the battery is fully charged, the battery management system itself separates it from the supply to prevent overcharging.

Linear Voltage Regulator:

For low power applications, a series or linear is often used. It is less efficient than a switching regulator, because the fluctuations in the supply voltage must be addressed, and the resulting power dissipated from the drop-volt transistor series but offers a pure DC. Series regulators are not suitable for high power applications such as electric traction in which the efficiency in mind.
Thyristor Voltage Control When powered by AC, s are used thyristors (SCR) in series with the load to a variable voltage to the blocking of the passage of current to the load for the first part of the cycle on and off the river by a signal to the gate creating the SCR. A single SCR affects only one polarity of the waveform. To change the positive and negative current will require two SCRs connected in parallel and in opposite polarity or a triac (bidirectional SCR). By varying the delay (phase angle) before the power is turned on can, the average current, and thus the average voltage seen by the load, be varied, as shown below.
This is the same principle as with dimmer switch.
Gate Turn Off Thyristor (GTO) can be used to turn power switching it on and that more control over the duration of the current through the device.
Current Control In many applications, the motor current the motor can supply through the inductor in the circuit was, and it is often desirable to control the current directly, rather than the voltage, or to obtain faster and more accurate control of the current and hence the torque. In this case, a shunt resistor or a current transformer is used to the current monitor. The difference between the actual and target currents in a high-gain feedback loop used to provide the necessary current regulation.
Current control is particularly important for induction motors in order to protect the motor against excessive start current. A current feedback signal is used to the firing angle of the thyristors in the rectifier or inverter circuits for limiting the current change in its reference value.

Converters:

This is a generic term for circuits that could provide AC or DC outputs from either AC (mains frequency) or DC (battery) supply lines. These include power bridges for the elimination of supply and AC supply inverters for generating an AC waveform from a battery.
Buck and Boost Converters Buck and Boost converters, DC / DC converters, the equivalent of AC DC transformers.
Buck Converter:

The buck converter is used to reduce the DC voltage. The chopper above is an example of a step-down DC converter.
Boost Converter The boost converter is used to increase voltage.
The route can Step up or step down the input voltage by varying the duty cycle of the switch transistor.
The transistor switch turns off the power supply voltage on the LC circuit on and off. When the transistor is to recharge the inductor and the diode cuts the capacitor. When the transistor switches, the inductor discharges through the diode, through the capacitor can charge up. Note that the polarity of the output voltage is the reverse of the input voltage. With a low load when the transistor is switched off for more than 50% of the time, the voltage that appears at the output is lower than the supply and the circuit acts like a step down transformer. With a high load when the transistor is switched on more than it is off, the tension builds on the capacitor and the output voltage of the supply voltage. Voltage control by varying the duty cycle is thus made available.

Traction batteries for EV and HEV Applications
Typical battery requirements apply traction Traction applications have traditionally been working for lead acid batteries, but the restrictions lead acid batteries, including the high cost alternative, which in turn limits the range of potential uses battery powered traction. A typical family car would have the battery capacity of about 40 kWh to provide one way to the 200 miles and 40 kWh of Lead Acid batteries weighs 1.5 tons.

The situation changes, however, the new battery chemistries and supporting technologies have created new technical solutions and economic benefits of making the battery pay for traction applications that were previously unprofitable and unrealistic. In particular, the use of lightweight nickel metal hydride and lithium batteries instead of the heavy and bulky lead acid batteries has a practical electric vehicles and hybrid electric vehicles, the possibility for the first time.

General requirements:

It is obvious that low cost, long time (more than 1000 cycles), low self discharge rate (less than 5% per month) and low maintenance costs are the basic requirements for all applications. Traction batteries usually operate under very difficult operating conditions and must withstand a wide temperature range (-30 ° C to +65 ° C), as well as shock, vibration and abuse. Low weight is not always a priority to ensure stability of the heavy weight of material handling equipment such as forklifts and handle the necessary aircraft tugs to tow heavy loads. However, low weight is essential to ensure high-capacity EV vehicles and HEV batteries used in passenger vehicles and that excludes the lead to these conclusions.
Circuit protection is also essential to the battery using a non-Lead Acid chemistries.

Purchase Specifications:
Traction batteries are very expensive and, like all batteries they deteriorated during their lifetime. Customers are demanding a minimum level of performance even at the end of battery life, so the buyer can specify the results expected by the end of life (EOL), and not the beginning of life (BOL). Under normal circumstances, applications for GE's ability EOL is defined as no less than 80% of the capacity of BOL. HEV applications for changes in the internal impedance is often used as an indicator of age. In this case EOL internal impedance can be defined as no more than 200% of BOL's internal impedance.
12 Volt Automotive SLI (starting, lighting and ignition) Battery Operating Requirements One deep discharge a short time (50% depth of discharge (DOD) with at least 5C rate), and then trickle charging. The battery is essentially always fully charged. No prolonged collaboration with the deep discharge. Typical capacity 0.4 - 1.2 kWh (33 Ah - 100Ah.) Maximum power 2.4 -3.6 kW (200 - 300 amperes).
PowerNet 36/42 Volt Battery Operating Requirements One of the deep discharge followed by intermittent heavy loads of electricity. No prolonged collaboration with the deep discharge. High efficiency and high cycle life necessary, especially if you stop / start functions used to run support. Tolerant to repeated high current pulses.are n Typical capacity of over 1 kWh. Peak power 5 to12 kW.
EV, HEV and PHV Battery Specifications The graph shows a comparison of the battery and the capacity requirements for a vehicle of the same size and weight, as EV, HEV or a PHEV configuration. Models of batteries can be optimized for power or capacity (energy content), but not both (see the energy trade-offs in the section Cell Construction), and therefore the type of cells used, and not just quantity, must be selected for use.
In the case of EV, the battery is the only source of power, and so the battery must be selected to achieve this power more or less continuously. EV capacity must be sufficient to achieve the required range, but also because it is not desirable to fully discharge the battery, a margin of about 20% is required to discharge depth shall not exceed 80%. Further margin of around 5% is also required to take regenerative braking charges a battery has just been charged. In othe words the battery should be directed to ensure the required capacity at the maximum SOC is 95% and up to 80% DOD. Continuous discharge rate of batteries are optimized for efficiency is typically about 1C, although some cells can tolerate pulsed currents to 3C or more for short periods. EV battery deep discharge usually one day from an intermediate topping the regen braking and the typical life of lithium-EV can be from 500 to 2000 cycles.

Corresponds to a series of hybrid batteries must also be able to provide the same power as the battery EV, because these vehicles are essentially the same size and weight, and intermittent periods of battery will be the only source of energy. However, due to global demand for energy is made available in an internal combustion engine (ICE) of the required battery capacity is much smaller. Parallel hybrids can have different arrangements for the sharing of power and so their energy requirements may be addressed by less battery power. HEVs, therefore an additional burden and complexity of the exercise about two power sources, each of which is large enough to power the vehicle on its own.
As a result, severe restrictions on the formula weight and size of the battery, which can be taken into account and HEV batteries are typically less than one-tenth the size of EV batteries used in the same vehicle size. Unavoidable consequence is that in order to obtain the same power of a battery one tenth the size of the HEV batteries must be able to supply current to 10C and more. Fortunately, the power is disconnected (but much longer than the required short pulse), because it is shared with ICE. Battery capacity is therefore less important than the supply of energy in hybrid vehicle, because the scope can be extended by a motor. Therefore, HEV batteries optimized for power.
The downside is that because of its low capacity of the HEV battery is constantly charged and discharged during normal operation and may be subject to the equivalent of one hundred per-discharge cycles per day. With deep discharge of the battery is, unfortunately, to be consumed within a few weeks. But we know that the life cycle of batteries is increasing exponentially in the DOD is limited (see the cycle of life and the DOD in the section on battery life) so that the HEV batteries must be carried out at partial DOD to extend the life cycle. This means that the battery capacity must be increased to allow for lower Dods although full capacity is almost never used. In this example, the HEV battery operates from 40% to 80% SOC. Longer working time can be achieved with even higher capacity batteries so that the desired capacity can be transported between the SOC ranged from 60% to 75%.

Plug in hybrids must work part time in EV mode, the depletion charge and part time in maintenance mode HEV fees. See detailed PHEV requirements below. PHEV battery requirements to be a compromise between energy storage and energy supply.
This is a major challenge for producers of the cells.

Variable Speed:

Self Excited Induction Generator (SEIG) Small systems of electricity generation are often stand alone applications, remote network of electricity supply, using widely fluctuating energy sources like wind and water for their source of energy. Generator fixed speed induction is not suitable for such applications. Generators at variable speed induction need some form of self excitation and packaging powerful to make practical use of their output voltage frequency and unregulated.
Operation Self excitation is obtained by connecting the capacitors to the terminals of the stator of the generator. When driven by an external prime mover, a small current is induced in the stator coils as flux due to residual magnetism in the cutting rotor windings and this current charges the capacitors. As the rotor turns, the flux cutting the stator windings will change in the direction opposite the orientation of the remanent magnetic field rotates with the rotor.

The current induced in this case is in the opposite direction and will tend to discharge capacitors. At the same time freed from the charge that the capacitors tend to reinforce the current increase in flow in the machine. As the rotor continues to turn induced emf and current in the stator windings will continue to rise until equilibrium is reached, according to the saturation of magnetic circuit in the machine. At this point the operating voltage and current will continue to oscillate at a given value peak and the frequency determined by the characteristics of the machine, the air gap, the slip, the calculation and choice of capacitor sizes .

The combination of these factors sets maximum and minimum speed range over which self-excitation occurs. The sheet of operation is generally low and the frequency variation depends on the speed range of operation.
If the generator is overloaded, the voltage will drop quickly provide a measure of the construction of self-protection.
Control Operating at variable speed induction generator needs a converter to adapt the output frequency variable generator fixed frequency of application or grid electricity. During operation of the controllable factor only available in a generator self-excited induction influence the output is the input mechanical mover, so that the system is not suitable for control of effective feedback.

Provide adjustable output voltage and frequency, external AC / DC / AC are required. A bridge with three diodes phase is used to correct the output current generator providing a current link three-phase thyristor inverter that converts energy from DC to link the required voltage and frequency.

DC generators (dynamos) Current (DC) Generator:
The field of stationary AC generator described above can be modified to provide unidirectional current by replacing the rings to slide on the rotor shaft of a collector adapted to reverse the connection to the coil each half cycle that passes Driver alternate north and south magnetic poles. However, power will be a series of half sine pulse, as the waveform from a rectifier as shown below.
Ripple output voltage can be minimized by using multi-plans.
The construction of a DC generator is very similar to the construction of a DC motor.
The rotor consists of an electromagnet to provide the excitement on the field. Current on the rotor is derived from the stator or in the case of large generators, from a separate excitation in rotation on the rotor shaft as well. Connection through the rotor is a switch so that the direction of current in the direction of the stator windings changes as the rotor poles crossing between northern and southern parts of the stator poles. The rotor is very low compared with the current in the stator windings and most of the heat is dissipated in the structure more massive stator.

In self-excited machines, when starting from rest, the current to start the electrical work is based on the small residual magnetism that exists in electro and around the magnetic circuit.

Automotive Alternators Generator automobile is a machine for variable speed AC issuing a fixed dc output.

Generator is a typical self excited alternating current machine. Using a generator rather than a DC generator using a switch and its potential reliability problems can be avoided. However, the current is required for all loads in the vehicle including the battery and, furthermore, the DC output voltage should be constant regardless of engine speed or load current. The charging system must include a rectifier to convert AC to DC and a regulator to maintain the tension generated within the independent design of the motor speed.

The rotor is driven by the engine and provides excitement on the field. Its speed is directly related to engine speed and depends on the ratios of the transmission or the drive pulleys. The output current is taken by the stator.

Automotive alternators are generally three phase machines to enable a compact design and at the same time, reducing the current in the stator windings by spreading it among three sets of windings. This also gives a reduction of the ripple voltage potential after correction.

Construction:

The rotor is a rotor claw pole in which both ends of the shape of the rotor north and south poles of an electromagnet. The "claws" extend them effectively produce parts in the north and south poles crossing poles of the stator. The rotor current energizing the electromagnet is supplied by the stator windings through three diodes auxiliary remedy before passing through two slip rings to a single rotor coil.
Moving magnetic field associated with the poles of the rotor causes a current to flow through the stator windings as the password field on the conductors of the stator.
The phase current produced by the alternator is rectified in a full wave, bridge circuit diode to produce a DC output. The EMF generator is directly proportional to the alternator (or engine) speed. The alternator is however designed to provide full voltage, typically 14.2 volts for a nominal 12 volt battery lead, at idling speed and maintain output voltage constant at that level that the engine increases speed.

Voltage Regulator:

To prevent the battery from being overloaded voltage DC output must be maintained below 14.2 volts maximum charge voltage specified for the battery. The function of the regulator senses the output voltage of the alternator and if it is greater than the voltage of 14.2 volts reference provided by a Zener diode, it interrupts the current field (rotor) coil . Not a current field of alternator voltage starts to fall. When the alternator voltage falls below the reference voltage, the current will be supplied to the field coil once again maintaining the output voltage at the desired level.

The rotor thus receives a pulsed DC on the speed range of engine operation, smoothed somewhat by the rotor winding inductance. Alternative designs to monitor the current load on the generator and provide a feedback mechanism using modulated pulse width to control the stator current to provide constant output voltage regardless of load.

Electric Drives:

Generators (Description and Applications)
The primary power of the world's electricity is generated in three-phase synchronous generators with machines with power up to 1500 MW or more. Design rules Despite the variety of electric generators is not as big as the wide range of electric motors available, they obey similar and most of the operating principles used in the various classes of electric motors, are also applicable to electrical generators. The vast majority of generators are machines (alternators), with a smaller number of DC generators (Zamalek).

Voltage and Frequency Regulation:

Most applications require some way control the generator output voltage and, in the case of an AC machine control method of the frequency. Voltage and frequency regulation is normally attained in the field of large machines that carry very high currents, controlling the excitation of the generator and the speed of the first engine driving the generator.

In smaller systems, particularly those designed to capture energy from intermittent energy flows such as wind and wave power voltage and frequency control can be done electronically. In principle, these control systems are similar to the engine controls and the various components are described in that section.

Generator Types
AC Generators (Alternators) :

Stationary Field Synchronous AC Generator In a stationary field generator, the stator in a fixed permanent magnets (or electromagnets powered by direct current) provides the magnetic field and current is generated in the windings of the rotor.
When the coil rotor rotates at constant speed in this field between the two poles of the stator the emf generated in the coil will be approximately sinusoidal, the actual waveform depends on the size and shape of the magnetic poles. The peak voltage occurs when the conductor is moving through the center line of the magnetic pole. Decreases to zero when the conductor is the space between the posts and increased to a peak in the opposite direction as the driver approaches the center line of the opposite pole of the magnet. The frequency of the waveform is directly proportional to the speed of rotation. The wave amplitude is proportional to the speed until the magnetic circuit saturates while the rate of increase of tension, as the speed increases, slows dramatically.
The output frequency is proportional to the number of poles and the rotor speed in the same way as a motor sychronous. See Table of engine speeds.
The current output generated alternating the rotor can be connected to external circuits via slip rings and does not need a switch.
Typical applications are portable AC generator with output power up to 5 kilowatts.
The rotating field synchronous AC generator The power management capabilities of a machine brushed, it is usually limited by the current handling capacity of the rings to slip in a car AC (or even more, the switch in a DC machine). Since the load current source is generally much higher than the current field, it is usually appropriate to use the rotor to create the field and take power from the generator stator to minimize the load on the rings slip .
Exchanging fixed and moving elements in the example above a generator rotating field is created in which the CEM is instead generated in the stator windings. In this case, in its simplest form, the field is provided by a permanent magnet (or electromagnet) that is rotated within a fixed cycle or coil of wire in the stator. The magnetic field in motion due to rotation of the rotor magnet will then cause a sinusoidal current flowing in the coil stator fixed the field moves beyond the stator conductors. If the field of rotor is provided by an electromagnet, will need to direct excitation current supplied through slip rings. Does not need a switch.
If instead of a single coil, three independent coils or the stator windings, spaced 120 degrees apart around the periphery of the machine are used, then the output of these coils are three-phase alternating current.
Series Wound Generator Classified as a generator at constant speed, they have poor voltage regulation and few are in use.
Shunt Wound Generator Classified as a constant voltage, the output voltage can be controlled by varying the field current. Reasonably good voltage regulation in the range of machine speed.
Brushless excitation Industry rotating machines are used for high power generation plants, in most systems of the world, the national grid. The power of excitement on the ground, these machines can be as large as 2.5% of the power (25 kW in a 1.0 MW generator), although this reduces the efficiency improves with the size so that a generator of 500 MW to 2.5 MW needs (0.5%) of power of excitation. If the voltage field is 1000 volts, the required field current will be 2500 Amps. Provide through the rings of excitement this shift is a technical challenge that was overcome by generating the necessary energy into the box itself by means of a pilot, three phase, stationary field generator on the same tree. The AC current generated in the windings of the pilot generator is rectified and fed directly to the windings of the rotor to provide excitation for the main machine.
Cooling The efficiency of a generator of large size can be as high as 98% or 99%, but for a generator of 1000 MW, with a loss efficiecy of just 1% means 10 megawatts of losses must be dissipated, primarily as heat. To avoid overheating, cooling, special precautions must be taken and the two forms of cooling are usually used simultaneously. The cooling water is circulated through copper bars in the stator windings and hydrogen is passed through the casing of the generator. Hydrogen has the advantage that its density is only 7% of air density with consequent loss of derivation of the rotor turning out less because the air in the machine and its thermal capacity is 10 times greater than air give him the ability to remove the heat higher.
Permanent Magnet AC Generators Smaller versions of both cars above can be used permanent magnets to provide magnetic field of the machine and the power is used to supply the industry, this means that the machines are simpler and more efficient. The disadvantage is however that there is no easy way to control this type of machine. Permanent magnet synchronous generators (PMSGs) are typically used in low-cost "power generators" to provide emergency power.
The voltage and output frequency of the permanent magnet generator is proportional to rotation speed, and although this may not be a problem for applications powered by a fixed speed drive mechanic, many applications such as wind turbines, require an output voltage fixed frequency, but are powered by variable speed prime movers. In these cases, complex control systems, feedback or external power conditioning may be required to provide the desired output stabilized.
In general, the output will be rectified and the output voltage variable supplied through the DC link to a dollar - reinforce that provides a fixed voltage regulator together with an inverter that provides a fixed output frequency.
Variable / Switched Reluctance Generators Similar in construction of the reluctance motor running, the generator is a doubly salient machine without magnets or brushes. As inert, iron poles of the generator rotor reluctance poles are pushed over the stator, the reluctance of the magnetic circuit evolution of the source is accompanied by a corresponding change in inductance of the stator poles, which in turn causes a current to be induced in the stator windings.

It would therefore be in a pulsed waveform appears at each pole of the stator. In machines polyphase results of each phase are fed to a converter that allows you to pass each stage sequentially to the DC link to provide a DC voltage. The system needs to detect the rotor position to control the timing of triggering the converter switches. These position sensors also allow the current to be controlled by varying the turn on and off the corners of the output current depending on the position of the rotor. As for the permanent magnet generator, Buck - boost regulators are also used to provide control over production.
The car unfortunately is not in itself self-exciting and different methods were adopted to enable the start, including the provision of an excitation current from a battery backup through the stator windings during start up or using small permanent magnets embedded in some of the poles of the rotor.
Features Compact, rugged design:
Variable speed operation.
The phases of the generator are completely independent.
Inexpensive to produce.
Because they have simple, inert without rotor windings or magnets embedded that can be driven at very high speeds and can operate in conditions of high temperature.
Suitable for models up to megawatts of capacity and speed of more than 50,000 rpm.
Applications:

Hybrid electric vehicle (HEV) drive systems, automotive starter generators, the generation of aircraft auxiliary power, wind generators, gas generators, high-speed turbine.

Motor Action:

Michael Faraday showed that passing a current through a wire freely suspended in a fixed magnetic field, a force that creates the conductor moving through the field causes. Conversely, if the conductor is not the magnet is then forced to create the magnet field will move in relation to the conductor.
Thus, in general, the force created by the current, now known as the Lorentz force between the conductors and the magnetic field or the magnetic field to create.
The size of the force on the conductor is given by:
F = BLI
Where F is the force on the ladder, L runs the length of the conductor and I the current through the conductor is
Generator Action:

Faraday also showed that the opposite is true - moving a conductor through a magnetic field or moving the magnetic field relative to the conductor, causing a current to flow into the pipe.
The size of the EMF is generated in this way, given by:
E = BLV
Where the generator emf E (or back EMF is in an engine) and v is the velocity of the conductor through the field

Alternative Motor Action (Interactive Fields):

Another form of motive power, which can not on the Lorentz force, and from the flow of an electric current, in principle, from the purely attractive (or repulsive) magnetic force which is exerted on a magnet or magnetically sensitive materials, as inferred be iron, if placed on the territory of another magnet. The movement of a compass needle in the presence of a magnet is an example. In practice, however, must create at least one magnet, the field of an electromagnet to achieve the necessary control of the magnetic field to the sustainable movement and at a practical level, the torque obtained.
Brushless DC motors and reluctance motors depends on this phenomenon as "reluctance torque", since no electric currents flow known in the rotor. Rotational movement is by sequential pulsing of the stator, a rotating magnetic field that drags along the moving-magnet with it will create.
For AC induction motors the rotating field is obtained by another method and the basic motor action depends on the Lorentz force, however, synchronous AC motors have magnet rotor elements are drawn to sync with the rotating field as in a brushless DC motor .

Reluctance torque:

Torque produced by the interaction of magnetic fields. Imagine a small bar magnet in the territory of another major magnet as the divide between the poles of a horseshoe magnet or the pole pair of an electric motor. (See chart reluctance motor). When the bar magnet with the poles of the great magnet focused its territory will be in line with the external field.

This is a state of equilibrium and the bar will not have any power to move it. However, if the bar is rotated out of alignment with the poles, either or moved, it is nevertheless a force once it moves into line with the external field. In the case of a lateral shift, it takes the power of the distance increases, but in case of a rotation will increase the force reaches a maximum when the bar is at right angles to the external field. In other words, the torque on the magnet is at a maximum when the fields are orthogonal and zero if the fields are aligned.
Salient poles Motors, which usually depend on the reluctance torque "salient poles - poles, which are outstanding. This is the river into sections focusing angle to maximize and focus the alignment of forces between the areas.
Torque of rotating fields For engines that depend on rotating fields, such as induction motors, brushless DC motors and restraint, the instantaneous torque depends on the rotor, from its angular position with respect to the angle of the flow wave. Although the flow wave tries to pull the rotor poles in line with the flow, there will always inertia and operating losses of the rotor back.
Slip:

The friction, windage and other losses cause the rotor of an induction motor at a slower speed than the rotating field which is associated to an angular misalignment between the rotating shaft and the rotational flow field with the rotor poles. The difference between the speed of the wave of the river and the speed of the rotor is called a "gaffe" and the torque of the motor is proportional to the slip.
Torque angle Even in the synchronous motors in which the rotor turns with the same speed as the flow wave, because of the aforementioned losses of the rotor poles will never achieve full alignment with the peaks in the flux wave, and there will be a shift between the rotating flux wave and the rotating field. Otherwise there would be no torque. This shift is called the "torque angle".

The torque of the motor is zero when the torque angle is zero and is at its maximum when the torque angle is 90 degrees. If the torque-angle exceeding 90 degrees, the rotor will pull out and stop synchronously.

Electrical machinery:

The majority of electrical machines (motors and generators) still sold today is based on the Lorentz force and its operations may be replaced by the following example, which turns a single-turn coil design electrical current in a magnetic field between the two poles, are shown a magnet. turn, several coils, the effective current NI (ampere turns), where N is the number of turns in the coil.
If the coil is supplied with a stream of machine that acts like a motor. If the coil is rotated mechanically, current is induced in the coil and thus the machine as a generator.

In rotating machines of the rotating element is called the rotor or armature and integral part of the stator is called.
Action and reaction In practice, both the engine and generator impact site at the same time.
Pass the effect of current through a conductor in a magnetic field that the line through the field, but once the conductor starts moving, it will create a generator to move a current through the pipe in the opposite direction to the current application. Thus, the movement of the head creates a "back EMF" which opposes the use of EMF.
Conversely, moving the ladder leads through the field to a current through the conductor which in turn exerts a force on the conductor applied force against the current.

The current flowing in the pipe, is given by:
I = (V - E)
R
Where V is the applied voltage, E is the back-EMF, and R is the resistance of the conductor.

Equilibrium operation under load To load the "action and reaction" effects described above an important automatic self-feedback mechanism in both DC and AC motors to adapt to changes in the application. As the engine load increases, it will tend to slow down, reducing the back EMF. This in turn allows more current to generate more torque to adapt to the increased load.

Magnetic Fields:

The motor of the magnetic field is made available through the stator and in the example above, the stator, a permanent magnet, but in the majority of electrical machines, the magnetic field by electromagnetic coils around the stator poles wound is provided. The stator windings are also in the field windings and the motor is said to be "illuminated box. The rotor is usually wrapped in an iron core to improve the efficiency of the magnetic circuit of the machine. Magnetic circuits In the case of electrical machinery, the magnetic circuit is the path of the magnetic flux through the stator body via the air gap, through the rotor and back through the air gap into the stator.

The length L of this path than the mean magnetic path length is known MMPI Magnetic circuits are designed to produce the maximum possible flow and concentrate it in the air gap between rotor and stator to move through the coils. The flux F measured in Webers The flux density B is measured in tesla and is as the magnetic flux F per unit area A. Thus defined, B = F / A, where A is the area through which the river flows.