Merits, Demerits and Applications of SRM

Merits of SRM

1. Construction is simple and robust.
2. Rotor carries no windings, no sliprings, no brushes, less maintenance.
3. There is no permanent magnets.
4. Ventilating system is simpler as losses takes place mostly in the stator:
5. Power semi conductor switching circuitry is simpler
6. No shoot through fault likely to happen power short circuits.
7. Developed torque doesn’t depends upon the polarity of current in the phase winding.
8. The operation of the machine can be easily change from motoring mode to generating mode by varying the region of conduction.
9. It is possible to get very high speed.
10. Depending upon the requirement T-ω characteristics can be achieved.
11. It is the self starting machine.
12. Energy stored in the phase winding is fed back to the supply through the feedback diodes during off period.

Demerits of SRM

1. Stator phase winding should be capable of carrying magnetising current also.
2. For high speed operations the developed torque has undesirable ripples. As a result develops undesirable noises (or) acoustic losses.
3. For high speed current waveform has undesirable harmonics. To suppress this effect large size capacitor is to be connected.
4. 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.
5. Size of the motor is comparable with size of variable speed induction motor drive.
6. 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.
7. It requires a rotor position sensor (RPS).

Applications

1. Washing machines
2. Vacuum cleaners
3. Future automobile applications
4. Fan
5. Robotics control applications