Synchronous watt:

The synchronous watt is defined as the torque developed by the motor such as the power input to the rotor across the air gap is 1 W while running at synchronous speed

The torque produced in the induction motor is given by

T= P2X60/2pi Ns

Here the torque is directly proportional to the rotor input,

By defining new unit of torque which is synchronous watt and that can be written as

T=P2 Synchronous watts

If the Torque is given in synchronous watts that can be obtained in N-m as

1 Syn-watt =60/2pi Ns  N-m

1 N-m = 2piNs/60 syn-watt