GATE 2022 : Electrical Machine Quiz 9

A 3- , 400 V, 50 Hz, 4 pole, Y connected induction motor has rotor resistance of 0.3 Ω per phase and rotor reactance 0.5 Ω per phase. The value of external resistance required that should be connected in rotor circuit such that maximum torque occurs at starting?

Consider 3-ϕ, 400V, 50Hz, 4 pole squired cage induction motor working at racked voltage and freq for same air gap flux if motor if fed from 30Hz, voltage of induction motor.

The transformation ratio of an auto transformer for a 30 kW, 400, 3-ϕ induction motor is______. If the starting torque is to be 75% of full load torque.

Assume the full load slip to the 5% and the short circuit current to be 6 times the full load current.

A 3-ϕ, star connected 400 V, 50 Hz, 4-pole induction motor has the following phase constants in ohms referred to stator:

R₁ = 0.3 Ω, X₁ = X₂’ = 0.35 Ω , R₂’ = 0.15 Ω, X_m = 35 Ω

Compute full load torque when motor is operated at rated voltage and frequency for a rated speed of 1440 rpm.

A 4-pole, 50 Hz, 6 kW, 3-phase induction motor develops rated torque at 1450 rpm. In case, the load torque is reduced to one-third of original load torque by keeping voltage, frequency and other parameter constant and assuming linear torque slip characteristics, the power output will be ________.

During the cascading connection of two induction motors, the input of second motor is  supplied through rotor output of first motor.

Motor 1 : 8 poles, Input frequency = 50 Hz

Motor 2 : 6 poles

The possible speeds are: