A three-phase, wye-connected, four-pole, 400- V, 60-Hz, 15-hp synchronous motor has a synchronous reactance of 3  per phase and negligible armature resistance. The data for its no-load magnetization curve follow:

Field current, A:

2  3.5  4.4  6  8  10  12

Line-to-neutral voltage, V:

100  175  200  232  260  280  295

(a) When the motor operates at full load at 0.8 leading power factor, determine the power angle and the ?eld current.Neglect all losses.

(b) Compute the minimum line current for the motor operating at full load and the corresponding ?eld current.

(c) When themotor runswith an excitation of 10 A while taking an armature current of 25 A, calculate the power developed and the power
factor.

(d) If the excitation is adjusted such that the magnitudes of the excitation voltage and the terminal voltage are equal, and if the motor is taking 20 A, ?nd the torque developed.