Consider a 460-V, 25-kW, four-pole, 60-Hz induction motor which has the following equivalent-circuit parameters in ohms per phase referred to the stator:

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The motor is to be operated from a variable frequency, constant-V/Hz drive whose output is 460-V at 60-Hz. Neglect any effects of rotational loss. The motor drive is initially adjusted to a frequency of 60 Hz.

a). Calculate the peak torque and the corresponding slip and motor speed in r/min.

b). Calculate the motor torque at a slip of 2.9 percent and the corresponding output power.

c). The drive frequency is now reduced to 35 Hz. If the load torque remains constant, estimate the resultant motor speed in r/min. Find the resultant motor slip, speed in r/min, and output power.

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R₁ = 0.103 R₂ = 0.225 X₁ = 1.10 X₂ = 1.13 Xm= 59.4 R₁ = 0.103 R₂ = 0.225 X₁ = 1.10 X₂ = 1.13 Xm= 59.4