SOLUTION

The speed regulation of a motor expresses how much its speed varies between no-load and full load. The synchronous motor runs at a constant speed whose magnitude is dependent on supply frequency and the number of poles.

The steady-state speed of the motor is constant from no load to the maximum torque that the motor can supply (called pull-out torque).

where

n_nl = no-load speed
n_fl = full load speed

Since the speed of the motor is constant hence its speed regulation is zero.