Three Phase Induction Motor
- It requires only three phase alternating supply. It is single excited motor.
- The speed of the Three phase induction motor decreases as the load on the motor increases.
- The induction motor runs at lagging power factor.
- The rotor of the induction may be wound or squirrel cage type.
- The induction motor is used for driving mechanical loads.
- The efficiency of induction motor is higher than that of synchronous motor for same voltage rating.
- The induction motor is known as asynchronous motor because it runs less than synchronous speed.
- The induction motor is used in industrial drives, textile industries, centrifugal pump, compressor etc.
Synchronous Motor
- It requires alternating supply for armature winding and DC supply for field winding. It is doubly excited motor.
- The speed of the synchronous motor remains constant. If the load increases beyond its specific rating, the motor becomes out of synchronous.
- The synchronous motor may runs at lagging, leading or unity power factor.
- The rotor of the synchronous motor may be cylindrical or projecting ( Salient ) type.
- It can be used for power factor correcting device. It is called as synchronous condenser when it is operated at leading power factor.
- The efficiency of synchronous motor is lower than that of induction motor for same voltage rating.
- The synchronous motor is cheaper than induction motor of low speed high power applications.
- The damper winding is used in the pole face of rotor in order to dampen oscillations.
- The application of synchronous machines for constant speed drives for compressors, blowers, fan and low head pumps.
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