Torque in the Synchronous Motor

Starting torque

• It is torque developed by the synchronous motor when name plate voltage is applied to its armature winding. It is also called as breakdown torque. 
• It may as low as 10% in the case of centrifugal pump.

Function of Damper Winding

• When the synchronous motor is driven for variable load such as shears, punching press, compressors etc., its rotor falls back or advance by some angle a . 
• When the load on the motor increases, its rotor falls back by some

Compare Squirrel Cage Induction Motor and Synchronous Motor

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.