5.29 The motor of Example 5.5 is running at rated (full-load) condition. The motor is stopped by
plugging (for rapid stopping)-that is, switching any two stator leads and removing the power
from the motor at the moment the rotor speed goes through zero. Determine the following, at the
time immediately after switching the stator leads:
(a) The slip.
(b) The rotor circuit frequency.
The torque developed and its direction with respect to rotor motion.
A 75-kW, 3-phase, Y-connected, 50-Hz, 440-V cylindrical rotor synchronous motor
operates at rated condition with 0.8 power factor leading. The motor efficiency,
excluding field and stator losses, is 95% and Xs = 2.5.2.
Draw the equivalent circuit model of the synchronous motor.
Determine the mechanical power developed, Pm- Pm= 78950
Determine the armature current, la Ia = 129A
Determine the back emf, Er. Ef= 516L-38
Determine the power angle, S. 8- -30
Determine the maximum or pull out power, P, m(max) Pm= 1572751 W
Determine the maximum or pull out torque, Tm(max) Tm= 1000 Nm
Draw the phasor diagram.
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