I need the answer as soon as possible 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 2and a standstill reactance of 1.2 2. Find the ratio of maximum torque to full-load torque and the speedat which maximum torque occurs.[5.27 A ; 3.3 A][2.6 ; 1125 r.p.m.]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 2 and the reactance atstandstill is 0.8 2. 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. A4-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 2 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[1444 r.p.m.; 937.5 r.p.m.][(a) 200 N-m (b) 0.82 (c) 1.6 2] (Elect. Machines-II, Vikram Univ. Ujjain 1977)6. A 50-Hz, 8-pole induction motor has a full-load slip of 4 per cent. The rotor resistance is 0.001 2per phase and standstill reactance is 0.005 2 per phase. Find the ratio of the maximum to the full-load torque and the speed at which the maximum torque occurs.[2.6; 600 r.p.m.] (City & Guilds, London)7. A 3-0, 50-Hz induction motor with its rotor star-connected gives 500 V (r.m.s.) at standstill betweenslip-rings on open circuit. Calculate the current and power factor in each phase of the rotor windingsat standstill when joined to a star-connected circuit, each limb of which has a resistance of 10 2 andan inductance of 0.03 H. The resistance per phase of the rotor windings is 0.2 2 and inductance0.03 H. Calculate also the current and power factor in each rotor phase when the rings are short-circuited and the motor is running with a slip of 4 per cent.[13.6 A, 0.48; 27.0 A, 0.47] (London University)8. A4-pole, 50-Hz, 3-phase induction motor has a slip-ring rotor with a resistance and standstill reactanceof 0.04 2 and 0.2 2 per phase respectively. Find the amount of resistance to be inserted in each rotorphase to obtain full-load torque at starting. What will be the approximate power factor in the rotor atthis instant ? The slip at full-load is 3 per cent.9. A 3-0 induction motor has a synchronous speed[0.084 2, 0.516 p.f.] (London University)250 r.p.m. and 4 per cent slip at full-load. Therotor has a resistance of 0.02 2/phase and a standstill leakage reactance of 0.15 Q/phase. Calculate(a) the ratio of maximum and full-load torque (b) the speed at which the maximum torque is devel-oped. Neglect resistance and leakage of the stator winding.[(a) 1.82 (b) 217 r.p.m.] (London University)10. The rotor of an 8-pole, 50-Hz, 3-phase induction motor has a resistance of 0.2 N/phase and runs at720 r.p.m. If the load torque remains unchanged. Calculate the additional rotor resistance that will[0.8 Q] (City & Guilds, London)11. A 3-phase induction motor has a rotor for which the resistance per phase is 0.1 2 and the reactanceper phase when stationary is 0.4 Q. The rotor induced e.m.f. per phase is 100 V when stationary.Calculate the rotor current and rotor power factor (a) when stationary (b) when running with a slip[(a) 242.5 A; 0.243 (b) 49 A; 0.98]12. An induction motor with 3-phase star-connected rotor has a rotor resistance and standstill reactanceof 0.1 2 and 0.5 N respectively. The slip-rings are connected to a star-connected resistance of 0.22 per phase. If the standstill voltage between slip-rings is 200 volts, calculate the rotor current per[19.1 A]13. A 3-phase, 50-Hz induction motor has its rotor windings connected in star. At the moment of startingreduce this speed by 10%of 5 per cent.phase when the slip is 5%, the resistance being still in circuit.

As per the guidelines of Bartleby we supposed to answer first question only.

Answered: 2. The star-connected rotor of an…

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...