Q23/ The rotor of a 4-pole, 50 Hz, 3-phase slip-ring induction motor has a resistance of 0.252/phase and runs at 1440 r.p.m. on full-load. Calculate the external resistance per phase which must be added to lower the speed to 1200 r.p.m. , the torque remaining constant in both cases. Ans[ 12] L024/ The resistance and stand nhase induction motor with star-

Q23/ The rotor of a 4-pole, 50 Hz, 3-phase slip-ring induction motor has a resistance of 0.252/phase and runs at 1440 r.p.m. on full-load. Calculate the external resistance per phase which must be added to lower the speed to 1200 r.p.m. , the torque remaining constant in both cases. Ans[ 12] L024/ The resistance and stand nhase induction motor with star-

Introductory Circuit Analysis (13th Edition)

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...

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K-1)The speed of a 3-phase wound-rotor induction motor can be changed by varying the amount of resistance in the rotor circuit. a) true b) false K-2). Which of the following statements are true about a 3-phase synchronous motor? a) It is a constant speed motor even under varying loads. b) It runs at the same speed the magnetic field rotates on the stator. c) It can correct its own, and the supply line's power factor d) all of the above K-3. A) What determines the speed of a 3-phase synchronous motor? a) the number of poles b) the frequency of the supply c) both "a" and "b" d) neither "a" nor "b" K-3)B) From a technician's standpoint, which of the following is the most practical method of providing a wide range of speed control for a 3-phase synchronous motor? a) by changing the frequency b) by changing the number of poles c) both "a" and "b" d) neither "a" nor "b"
The rotor of the 4-pole three-phase squirrel cage induction motor has been replaced with the rotor of the three-phase 4-pole rotor wound induction motor. When the motor is fed with normal supply, the machine will a) Does not work b) Runs at a very slow pace c) Runs at slightly lower speed than normal speed d) Runs at a slightly higher speed than normal speed e) none
Q2] Fill in the blank (9 Marks) 1-The current drwan by the armature of D.C. motor is directly proportional to 2- The speed of a D.C. shunt-wound motor will shunt field regulator is increased. 3- The synchronous speed of a three-phase induction motor is number of pairs of poles. Rotor copper losses Rotor input power in induction motor = 5- A 4-pole three-phase induction motor has a synchronous speed of 25 r.p.s. The frequency of the supply to the stator is_ Hz. 6- The power input to a mains transformer is 200VA. If the primary current is 2.5A, the secondary voltage is 2V and assuming no losses in the transformer, the turns ratio step down. is 7- A 200kVA transformer has an iron loss of 1 kW and full load cu loss of 2 kW. Its load kVA corresponding to maximum efficiency is kVA. 8- If cu loss of a transformer at 7/8th full load is 4900 W, then its full-load cu loss would be watt. 4- if the value of resistance of the proportional to the 9- The slight curvature at the lower end of the open…
A 400 V, 50 Hz 30 hp, three-phase induction motor is drawing 50 A current at 0.8 power factor lagging. The stator and rotor copper losses are 1.5 kW and 900 W respectively. The friction and windage losses are 1050 W and the core losses are 1200 W. The air-gap power of the motor will be
A 240 V series motor develops a torque of 120 Nm at a speed of 900 rpm. The armature winding resistance is 0.20 and the series field winding resistance is 0.1 Q. For a constant load torque find the new speed of the motor when a diverter resistance of 0.1 Q is placed across the series field winding.
A three-phase induction motor used for a commercial application in Oman 50HZ runs at 584 rpm at no load and at 546 rpm at full load. a) How many poles do this motor have? b) What is the percentage slip at full load? c) The frequency of the rotor currents when slip is 7 % d) The frequency of the rotor currents at standstill.
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3. A 440V 60-hp six pole 60 hz A connected induction motor has the following parameters R1=0.048 R2= 0.035 Xm= 9.50 X1= 0.33 0 X2= 0.37 0 Pcore= 600W PF&W= 350W Use the Thevenin's Equivalent circuit concept to find: (a)Vth and Zth seen by the rotor circuit (b)The slip at which maximum torque occurs (c) the value of Max/pullout Torques (d) The starting torque.
Q.14. What is slip in an induction motor? Q.15. What is the value of slip at start in an induction motor?
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