NEMA dedines pull-out torque of a synchronous motor as the maximum sustained torqe which the motor will develop at synchronous speed for one minute at rated frequency and normal excitation.
normal pull-out torqe is usually 150% of full load torqe for unity power factor motor and 200%
to 225% for 0.8 leading power factor motors. It can be increased by increasing thefield strength,which generally means increasing the air-gap and flux density. This usually means increasing the physical size of the motor.