In a synchronous motor, the starting torque is:

Types of Torque in the Synchronous Motor

1.) Breakaway torque

• The torque that is developed at the starting time of the motor is known as the breakaway torque.
• It is torque developed by the synchronous motor when nameplate voltage is applied to its armature winding.
• It may be as low as 10% in the case of a centrifugal pump. 

2.) Running torque

• It is torque developed by the synchronous motor under running conditions.
• The full load torque of the motor is called running torque. 
• It is determined by horse power and the speed of the motor.

3.) Pull-in torque

• A synchronous motor is started as an induction motor during starting conditions and its speed is below 2 to 5% of the synchronous speed. ​
• When the excitation ( or DC supply ) to the field winding is applied, the motor pulls into synchronism resulting stator and rotor magnetic field rotating at the same speed.
• The amount of torque required for a synchronous motor to pull into synchronism is called pull-in torque.

4.) Pull-out torque

• Pull-out torque is the maximum torque that can be delivered without losing steps.
• It reaches its maximum at the lowest frequency or speed and decreases as frequency increases.