Merits of SRM
- Construction is simple and robust.
- Rotor carries no windings, no sliprings, no brushes, less maintenance.
- There is no permanent magnets.
- Ventilating system is simpler as losses takes place mostly in the stator:
- Power semi conductor switching circuitry is simpler
- No shoot through fault likely to happen power short circuits.
- Developed torque doesn’t depends upon the polarity of current in the phase winding.
- The operation of the machine can be easily change from motoring mode to generating mode by varying the region of conduction.
- It is possible to get very high speed.
- Depending upon the requirement T-ω characteristics can be achieved.
- It is the self starting machine.
- Energy stored in the phase winding is fed back to the supply through the feedback diodes during off period.
Demerits of SRM
- Stator phase winding should be capable of carrying magnetising current also.
- For high speed operations the developed torque has undesirable ripples. As a result develops undesirable noises (or) acoustic losses.
- For high speed current waveform has undesirable harmonics. To suppress this effect large size capacitor is to be connected.
- The airgap at Aligned axis has to be very small by the airgap at the interpolar axis should be very large. It is difficult to achieve.
- Size of the motor is comparable with size of variable speed induction motor drive.
- Number of power wires between the power semiconductor circutary & the motor and number of control cables from the controller to the power semiconductor switching circutary are more.
- It requires a rotor position sensor (RPS).
- Washing machines
- Vacuum cleaners
- Future automobile applications
- Robotics control applications