2. The star-connected rotor of an induction motor has a standstill impedance of (0.4+j4) ohm per phaseand the rheostat impedance per phase is (6+j2) ohm. The motor has an induced e.m.f. of 80 Vbetween slip-rings at standstill when connected to its normal supply voltage. Find (a) rotor current atstandstill with the rheostat in the circuit (b) when the slip-rings are short-circuited and the motor isrunning with a slip of 3%.3. A4-pole, 50-Hz induction motor has a full-load slip of 5%. Each rotor phase has a resistance of 0.3 Qand a standstill reactance of 1.2 Q. Find the ratio of maximum torque to full-load torque and the speedat which maximum torque occurs.4. A 3-phase, 4-pole, 50-Hz induction motor has a star-connected rotor. The voltage of each rotor phaseat standstill and on open-circuit is 121 V. The rotor resistance per phase is 0.3 and the reactance atstandstill is 0.8 N. If the rotor current is 15 A, calculate the speed at which the motor is running.Also, calculate the speed at which the torque is a maximum and the corresponding value of the inputpower to the motor, assuming the flux to remain constant.5. A 4-pole, 3-phase, 50 Hz induction motor has a voltage between slip-rings on open-circuit of 520 V.The star-connected rotor has a standstill reactance and resistance of 2.0 and 0.4 Q per phaserespectively. Determine :(a) the full-load torque if full-load speed is 1,425 r.p.m.(b) the ratio of starting torque to full-load torque(c) the additional rotor resistance required to give maximum torque at standstill[5.27 A ; 3.3 A][2.6 ; 1125 г.p.m.][1444 г.р.m.; 937.5 г.р.m.][(a) 200 N-m (b) 0.82 (c) 1.6 N] (Elect. Machines-II, Vikram Univ. Ujjain 1977)

Answered: Image /qna-images/answer/33725f3d-8adc-449f-832f-3e0bb33304d8.jpg

2. The star-connected rotor of an induction motor has a standstill impedance of (0.4+ j4) ohm per phase and the rheostat impedance per phase is (6+j2) ohm. The motor has an induced e.m.f. of 80 V between slip-rings at standstill when connected to its normal supply voltage. Find (a) rotor current at standstill with the rheostat in the circuit (b) when the slip-rings are short-circuited and the motor is running with a slip of 3%. [5.27 A ; 3.3 A]

2. The star-connected rotor of an induction motor has a standstill impedance of (0.4+ j4) ohm per phase and the rheostat impedance per phase is (6+j2) ohm. The motor has an induced e.m.f. of 80 V between slip-rings at standstill when connected to its normal supply voltage. Find (a) rotor current at standstill with the rheostat in the circuit (b) when the slip-rings are short-circuited and the motor is running with a slip of 3%. [5.27 A ; 3.3 A]

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter2: Fundamentals

Section: Chapter Questions

Problem 2.21P: An industrial plant consisting primarily of induction motor loads absorbs 500 kW at 0.6 power factor...

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