
120 Shipboard Electrical Power Systems
Therefore, the torque angle δ = – 22.67° at rated load. The negative sign indicates
that the counter emf lags the voltage applied at the terminals, that is, the rotor
magnetic field lags (follows) the stator magnetic field. In the synchronous genera-
tor, the opposite is true.
The synchronous motor performance analysis under mechanical load is similar to
that of the synchronous generator, resulting in the torque output at the motor shaft
given by
T
motor
= T
max
sinδ (5.13)
where T
max
= maximum (pullout) torque the motor can develop, and δ = torque
angle (electrical degrees). The T
motor
versus δ plot