4) It is advisable to avoid line-starting of induction motor and use starter because: A. motor takes five to seven times its full load current B. it will pick-up very high speed and may go out of step C. it will run in reverse direction D. starting torque is very high E. starting speed is very high 5) In a three-phase induction motor, the number of poles in the rotor winding is always: A. zero B. more than the number of poles in stator C. less than number of poles in stator D. equal to number of poles in stator E. two 6) DOL starting of induction motors is usually restricted to: A. low horsepower motors B. variable speed motors C. high horsepower motors D. high speed motors A variable torque motors

4) It is advisable to avoid line-starting of induction motor and use starter because: A. motor takes five to seven times its full load current B. it will pick-up very high speed and may go out of step C. it will run in reverse direction D. starting torque is very high E. starting speed is very high 5) In a three-phase induction motor, the number of poles in the rotor winding is always: A. zero B. more than the number of poles in stator C. less than number of poles in stator D. equal to number of poles in stator E. two 6) DOL starting of induction motors is usually restricted to: A. low horsepower motors B. variable speed motors C. high horsepower motors D. high speed motors A variable torque motors

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter35: Harmonics 916

Section: Chapter Questions

Problem 3RQ: Would a positive-rotating harmonic or a negative-rotating harmonic be more harmful to an induction...

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Similar questions

Name three factors that determine the torque produced by an induction motor.
6- Which of the following supply is given to the rotor winding of 3-Phase Induction Motor: a) DC Supply b) AC Supply c) No Supply d) Pulsating Supply 7- 3-Phase Induction Motor will have Starting Torque and Starting Current a) High, High b) Low, Low. c) High, Low d) Low, High 8- Which of the following method is used for controlling the speed of an induction motor: a) Changing number of stator poles b) Supply voltage control c) Frequency control d) All the options are correct 9- Which of the following method cannot be used for starting of 3-Phase Squirrel Induction Motor: a) Star-Delta Starting b) Line resistor startling c) transformer Starter d) Rotor Resistance Starting 10- The rotor of a stepper motor has no: a) windings b) commutator c) brushes d) all of the above
L-1). The 3-phase wound-rotor induction motor has .... . a) high starting torque b) low starting current c) both "a" and "b" d) neither "a" nor "b" L-2). The 3-phase wound-rotor induction.........a) motor has a wire wound rotor b) motor's rotor can be connected to an external resistive load by way of slip rings and brushes c) motor requires more maintenance than the 3-phase squirrel-cage induction motor d) all of the above L-3). The 3-phase wound-rotor induction motor's rotor circuit's resistance should be adjusted so it is__________ during starting. a) low b) high c) either "a" or "b" d) neither "a" nor "b" L-4). Will a 3-phase wound-rotor induction motor start with no external circuit connected to its rotor leads? a) yes b) no
What are the various losses in an induction motor? On what factors do they depend? IV. V. List the different types of stray load losses in an induction motor.
B/ Fill in the blanks: TV ezur 1- In a three-phase induction motor iron losses in stator will be..... that in rotor. 2- In three-phase induction motors sometimes copper bars are placed deep in the rotor to........... 3- Blocked rotor test on induction motors is used to find out. R..., ke, X. 4- The maximum torque in an induction motor depends on .............and .....
An 3-phase induction motor(IM) has full load slip = 0.5%. If the rotor circuit resistance is increased so that R2new =2R2old, then the slip at which the motor develops the same full load torque is=.. * ......
Q3) I. What' s the effect of The auxiliary winding of split - phase induction motor when it becomes short circuit ?
Q.14. What is slip in an induction motor? Q.15. What is the value of slip at start in an induction motor?
An 8 pole, 50 Hz slip ring induction motor runs at a slip of 2.67% on full load. The rotor resistance per phase of the winding is 0.2 ohm. What external resistance per phase must be added in the rotor circuit so that the motor now runs ate a slip of 17.33% such that the torque remains same in both the cases. (Ans: 1.1 ohm)
Frequency of emf in the stator of a 8 pole induction motor is 50Hz and the rotor emf frequency is 1Hz. The motor speed is ................ Answer
A three-phase induction motor used for a commercial application in Oman runs at 580 rpm at no load and at 552 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 5 % d) The frequency of the rotor currents at standstill. a) b) c) d)
Example -4. A three-phase. 60-Hz induction motor runs at 890 r/min at no load and at 840 r/min at full load. (a) How many poles does this motor have? (b) What is the slip at rated load? (c) What is the speed at one-quarter of the rated load? (d) What is the rotor's electrical frequency at one-quarter of the rated load?