Direction: The following item consists of two statements, one labelled as ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answer using the code given below:

Statement (I): Synchronous motor is a constant speed motor.

Statement (II): Synchronous motor is not a self-starting motor.

Speed:

Synchronous motor run at the synchronous speed of the supply. Synchronous motors are constant speed motors. They are generally used for constant speed operation under no-load conditions such as to improve the power factor.

Self-Starting Property:

• At the start the rotor is stationary and take a positive cycle of AC supply, N pole of the stator (Ns) is opposite to N pole of the rotor (Nr)
• The repulsion on the rotor will move clockwise or counterclockwise
• Now Take negative half cycle N pole of the stator will become S pole
• Now S pole of the stator (Ss) will attract N pole of the rotor (Nr)
• Because of attraction, during the negative cycle and repulsion during the positive cycle, the resultant rotation is zero
• So resultant torque is zero
• So synchronous motor is not self-starting

Therefore, Both Statement I and Statement II are individually true but Statement II is not the correct explanation of Statement I.