Exams › GATE › Technical

A 230 V, 50 Hz, 4-pole, single-phase induction motor is rotating in the clockwise (forward) direction at a speed of 1425 rpm. If the rotor resistance at standstill is 7.8 Ω, then the effective rotor resistance in the backward branch of the equivalent circuit will be

1. (A) 2 Ω
2. (B) 4 Ω
3. (C) 78 Ω
4. (D) 156 Ω

Correct answer: (A) 2 Ω

Solution

Ns=1500 rpm, so slip s=(1500-1425)/1500=0.05 and backward slip 2-s=1.95. The effective rotor resistance in the backward branch is R2/[2(2-s)] = 7.8/(2 x 1.95) = 2 ohm.

Related GATE Technical questions

• The equivalent circuits of a diode, during forward biased and reverse biased conditions, are shown in the figure. If such a diode is used in clipper circuit of figure given above, the output voltage (vₒ) of the circuit will be
• An input device is interfaced with Intel 8085A microprocessor as memory mapped I/O. The address of the device is 2500H. In order to input data from the device to accumulator, the sequence of instructions will be
• Distributed winding and short chording employed in AC machines will result in
• In a stepper motor, the detent torque means
• A two machine power system is shown below. Transmission line XY has positive sequence impedance of Z1 Ω and zero sequence impedance of Z0 Ω. An ‘a’ phase to ground fault with zero fault impedance occurs at the centre of the transmission line. Bus voltage at X and line current from X to F for the phase ‘a’, are given by Va Volts and Ia Amperes, respectively. Then, the impedance measured by the ground distance relay located at the terminal X of line XY will be given by
• The impulse response of a causal linear time-invariant system is given as h(t). Now consider the following two statements: Statement (I): Principle of superposition holds Statement (II): h(t) = 0 for t < 0 Which one of the following statements is correct?

⚔️ Practice GATE Technical free + battle 1v1 →