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In a 3-phase induction motor, the rotor induced EMF per phase (Er) is equal to:

(Where Eo is rotor induced EMF at standstill and s is slip)

This question was previously asked in
MPPGCL JE Electrical 19 March 2019 Shift 2 Official Paper
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  1. sEo
  2. Eo
  3. \(\frac{E_{o}}{s}\)
  4. sEr

Answer (Detailed Solution Below)

Option 1 : sEo
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Detailed Solution

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Concept

The EMF induced in the rotor of an induction motor is given by:

\(E_r=sE_o\)

where, Er = Rotor induced EMF

Eo = Standstill EMF

s = Slip

The slip 's' is given by:

\(s={N_s-N_r\over N_s}\)

Ns = Synchronous speed

Nr = Rotor speed

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More Induction Motor Torque Questions

Q1. In a 3-phase induction motor, the rotor induced EMF per phase (Er) is equal to: (Where Eo is rotor induced EMF at standstill and s is slip)
Q2.In a three-phase squirrel-cage induction motor, the increased starting torque can be obtained by: A) Using deep-bar rotors B) Increasing the frequency of operation C) Increasing the number of poles D) Using a double-cage rotor
Q3.The starting torque of a slip ring induction motor is maximum when rotor resistance/phase is ________ rotor reactance/phase.
Q4.If the rotor resistance in an induction motor is decreased, then maximum torque will occur at: 
Q5.The maximum starting torque of a 3-phase induction motor occurs when:
Q6.A 746 kW, 8-pole, 3-phase, 50 Hz induction motor has a rotor resistance of 0.04 Ω per phase and standstill rotor reactance of 0.3 Ω per phase. Full load torque is obtained at 720 rpm. What is the ratio of maximum to full load torque?
Q7.The starting torque in a three phase induction motor, will be the maximum when, \(\rm \frac{rotor \ restistance \ per \ phase}{rotor \ reactance \ per \ phase}=?\)
Q8.A 746 kW, 3-phase, 50 Hz, 16-pole induction motor has a rotor impedance of (0.02 +j 0.15) Ω at standstill. Full load torque is obtained at 360 rpm. Calculate the speed at which maximum torque occurs.
Q9.The torque of an induction motor depends on the strength of fields and phase relation between them. The torque which is developed is directly proportional to which of the following entities?
Q10.The starting torque in a three-phase induction motor, will be maximum when, \(\rm rotor~resistance~per~phase \over rotor~reactance~per~phase\)=?

More Three Phase Induction Motor Questions

Q1.If a 6-pole induction motor operates on a 60 Hz supply, its synchronous speed is _____________.
Q2.Crawling typically causes an induction motor to operate at a speed that is: 
Q3.Which of the following modifications increases the ratio of full load torque to maximum torque in an induction motor?
Q4.In a three-phase induction motor which component represents mechanical load in the equivalent circuit?
Q5.Which of the following is a key characteristic of a slip ring induction motor?
Q6.In a Star-Delta Starter used for induction motors, the starting torque is reduced to approximately:
Q7.A three-phase induction motor is operating at a slip of 0.05 at full load. During the run, if the phase sequence of the supply is reversed, then what is the slip at the instant of reversal?
Q8.A three-phase, 440 V, 6 pole, slip ring induction motor operates with 2% slip and takes a stator current of 50 A. The speed of the motor is reduced at constant torque to 500 rpm using stator voltage control. The new value of the stator current will be _________.
Q9.A 400 V, 50 Hz, three-phase induction motor runs at a slip of 0.06 when it is driving a constant load torque. With what slip will it run driving the same load if the voltage applied is reduced to 200 V, neglecting stator resistance and the equivalent reactance of the motor?
Q10.A 3-phase induction motor runs at 600 rpm when connected to a 3-phase, 60 Hz supply. Find the number of poles.
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