Stator input = stator output + losses
Rotor input = stator output[stator output is transferred entirely inductively to the rotor circuit]
Rotor gross output = rotor input – rotor copper losses.
This rotor output is converted into mechanical energy and gives rise to gross torque Tg. Out of this gross torque developed, some is lost due to windage and friction losses in the rotor and the rest appears as the useful or shaft torque Tsh. If Tg is in N-m and N is the actual speed of the rotor in r.p.m.