For any load conditions as represented by Fig.1, the output per phase is P = V I cos°. The electrical power converted from mechanical power input is per phase
P1 = EtI cos (° σ) (32)

Resolving Et along I

P1 = EtI cos ( ° σ) = (V cos° Ir).I = V I cos° I2R (33)

The electrical input is thus the output plus the I2R loss, as might be expected. The prime mover must naturally supply also the friction, windage and core losses, which do not appear in the phasor diagram.