Tuesday, August 25, 2009

Reluctance:
Features:-
No I2R loss in the rotor.
Inert rotor.
No permanent magnet.
Compact size and light weight.
Low cost.
Efficiencies of more than 90%.
Inexpensive and easy to manufacture.
Low complexity of building an engine.

Many of stamped metal elements.
High reliability (no brush wear).

Robust construction.
High efficiency.
High initial investment

torque and high-speed operation possible.

Applications:

Available with capacities up to thousands of amps and hundreds of kilovolts.
The automotive industry now makes extensive use of variable reluctance motors for applications such as traction drives, power steering, pumps and windscreen wipers.
3 or 4-phase motors for scooters and fans are used.
High-speed pumps and compressors.
Household appliances.
See also integrated starter-generator.

Stepper Motors:
The stepper motor, which some of the features of modern switched reluctance motor includes invented and patented in 1920 in Aberdeen by CL Walker

A stepper motor is a special case of a variable reluctance motor or a permanent magnet brushless DC motor. Instead of a constant, repetitive stream of pulses, the motor can be strengthened to make an impulse at a time so that the motor is supplied at very precise angles rotations.The motor, reversible, to go positive momentum causes a rotation in one direction while the engine go negative impulses in the opposite direction.
When the engine is equipped with a threaded spindle can be used to make a precise linear displacement coupled.

The pulses can be generated by a voltage controlled oscillator (VCO), but the design is particularly suited for digital and microprocessor controllers.
All these factors make the stepper motor is ideal for industrial robotics, machine tools and process controls.

The stepping angle through which each pulse is given by:
Step angle = 360 °
(Rotor Teeth) X (stator phases)

Position control is simply by counting the pulses and complex closed-loop feedback systems are possible, not necessary that the basic operation. ) For further control (small angle can be achieved by stacking and to compensate for several rotors and stators in a single rotor shaft.

For long movements, it may be desirable to control the speed during the operation, to accelerate to a maximum speed then slows as the proposed target is approached. For such applications, a speed control can be added.

Stepper motors are used as permanent magnet (PM), variable reluctance (VR) or hybrid specified (a combination of PM and VR).
Features:
Precise control of position.
Simple attitude control opened.
Accessible to control simple computer.
Applications:
Used computers on the plotters and printers.
Industrial control.
Numerically controlled machine tools.
Robotic systems.

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