A 440-V, 60-Hz, 4-pole, Delta-connected, three-phase induction motor has the following parameters in ohms/phase referred

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A 440-V, 60-Hz, 4-pole, Delta-connected, three-phase induction
motor has the following parameters in ohms/phase referred to the
stator circuit: R1 = 0.3 ohms, R2 = 0.6 ohms, X1 = 0.9 ohms,
X2 = 0.9 ohms, Rc = 150 ohms, Xm = 60 ohms. The rotational
loss is 4% of the power developed. If the motor runs at 4% slip,
Determine:
a) rotor speed
b) stator current
c) power factor
d) efficiency
e) the slip at which the motor develops maximum torque
f) if the rotational losses are kept constant at 500 W, what is
the required rotor current to operate the motor at maximum
efficiency?