Electric motors - DC Motors :

Description and Applications :
Brushed (Field energized) Engines (engines with wound rotors) The traditional DC motor has two current supply, one by the stator windings to the magnetic field to offer and the other by the rotor windings to interact with the magnetic field to generate the driving force. There are three ways to reach each one unique feature results in motor performance. Because they all wound rotors use, they all need a collector at the current feed into the rotor windings.
The speed is controlled by varying the rotor voltage and thus the rotor current, or by varying the magnetic flux in the air gap by changing the current in the field windings.
With access to both the field and the rotor windings, all DC motors offer the possibility of simple speed and torque control.
Series Wound The series wound motor has only one power supply to the engine and the field winding is connected in series with the rotor winding.
Features:

The series has a bad motor speed control. It provides more torque with increased engine power but at the expense of speed, which falls with increasing torque requirements.
This engine has a very high starting torque because there is zero EMF zero as the speed builds but does the back EMF causes a reduction in torque. Increasing the load on the engine tends to slow down, but this in turn reduces EMF and torque increases with the tax concerns.
Speed control is possible by varying the voltage. Under no load conditions the speed will accelerate to dangerous levels likely caused the destruction of the engine. The motor can be reversed by reversing the connections to both the field or rotor windings, but not both.
Regenerative braking is not possible because the area's current needs to be maintained, but it collapsed when the rotor current passes through zero and vice versa.
Applications:

Series DC motor is an industrial workhorse for both high and low power, fixed and variable speed electric drives. Applications range from cheap toys for applications in the automotive sector.
They are cheap to produce and are used in variable speed domestic appliances such as sewing machines and power tools.
Its high torque makes it particularly suitable for a wide range of traction applications.
Shunt Wound The shunt wound motor has also only one power supply to the engine, but in this case the winding is connected in parallel with the rotor winding.
Field Weakening:

The speed of a shunt wound motor can be controlled to a limited extent without affecting the power supply by "field weakening". A rheostat in series with the winding field can be used to reduce the current field. This in turn reduces the flux in the air gap and as the speed is inversely proportional to the flow, the engine speed. But the torque is directly proportional to the flux in the air gap, so the speed increase will be accompanied by a reduction of torque.
Features:

The shunt wound motor is running at nearly constant speed as the voltage is fixed. The engine can deliver more torque, without a noticeable reduction in speed, by increasing the motor current. Like the series wound motor, the shunt wound motor be reversed by reversing the connections to both the field or rotor windings.
Regenerative braking is possible. Self excitation maintains the field in the rotor flow reverses.
Applications:

Fixed speed applications such as windshield wipers of cars and fans.
Separately Excited The separately excited motor has independent power of the field and the rotor windings allowing more control over engine performance.
Features The voltage on either the field or the windings of the rotor can be used to the speed and torque of a separately excited motor.
Applications Train and car-traction applications:
Permanent Magnet Motors As the name suggests, these motors use permanent magnets instead of electromagnets to either the rotor or the stator field. They are widely used in small DC motors and increasingly in traction applications.
Rotor Magnets These are by far the most common types of permanent magnet motors. They have no rotor windings but use permanent magnets on the rotor field supply and they act as a shunt wound DC motors with a fixed current shunt.
Their big advantage is the elimination of the commutator.
Field Magnets These motors have no territory, but the liquidation using permanent magnets to the magnetic field to offer. News is still supplied to the rotor via a collector in other brushed motors and speed can be controlled by varying the voltage to the rotor windings. In this way their behavior is similar to a series wound DC motor.

Permanent magnet motors are studied in more depth in the section on brushless DC motors

Universal Motors In a series wound DC motor, reversing both the field winding leads and rotor winding turns leading the direction of the motor. Yet reversing the leads of the power supply will not affect the direction of rotation, since it is equivalent to reversing the current through both the individual windings - in effect a double reversal. In other words, the engine back in the same direction, although the current through the coils series is reversed. This means that the engine can run on AC and DC, since the direction of rotation is independent of the direction of the flow through the series windings.
Universal motors are often used in power tools and household appliances such as vacuum cleaners and food mixers. For more information on universal motors.