10- What is the ratio of rotor input power to rotor copper loss in an induction motor? a) 1/(1-S) b) 1 - S c) 1/S d) S 11- If the frequency of 3-phase supply to the stator of a 3-phase induction motor is increased, then synchronous speed a) Increased b) Decreased c) Remain unchanged d) None of the above

10- What is the ratio of rotor input power to rotor copper loss in an induction motor? a) 1/(1-S) b) 1 - S c) 1/S d) S 11- If the frequency of 3-phase supply to the stator of a 3-phase induction motor is increased, then synchronous speed a) Increased b) Decreased c) Remain unchanged d) None of the above

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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Would a positive-rotating harmonic or a negative-rotating harmonic be more harmful to an induction motor? Explain your answer.
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
1. The operation of Commutator in DC Motor is * O a) to convert dc to ac O b) to convert ac to dc O c) to convert fixed dc to variable dc O reverse the current direction in the rotating windings each half turn
If a 4-pole induction motor has a synchro- nous speed of 1500 r.p.m., then, supply fre- quency is (1) 50 Hz 60 Hz (iii) (ii) 25 Hz (iv) none of the above
T-a. The direction of rotation of a single-phase split-phase motor can be change by........ a) reversing the connection of the start winding b) reversing the connection of the run winding c) reversing the connection of the start and run winding at the same time d) "a" or "b", not "c" T-b. Single-phase split-phase motors using an electrolytic capacitor in the start winding circuit should not be cycled more than about__________ time per hour. a) 8 b) 12 c) 24 d) none of the above T-c. When replacing the capacitor in a capacitor-start induction-run motor, one must be sure to replace the bad capacitor with__________ . a) a smaller one b) one of the same size c) a larger one d) none of the above
7- Iron loss in the rotor of a 3-phase induction motor is negligible due to (a) Very low frequency of emf induced in the rotor (c) Very low flux density in rotor parts 8- The starting current of a 3-phase induction motor is about (a) Half (c) 5 to 7 times (b) Twice (d) 8 to 10 times 9- During plugging of an induction motor (a) Phase sequence is reversed (b) A de source is connected to stator (e) One phase is open circaited (d) Power is ied back to mains 10- Direct online (D.O.L.) starter is used for induction motors (a)Less than 5 h.p. (b) Less than 10 h.p. (c) Greater than 10 h.p. (d) For any capacity (b) Very low emf induced in the rotor (d) Constant magnitude of flux linking the rotor core of its full load rated current
8. A 3-phase induction motor is running at 2% slip. If the input to rotor is 1000 W, then mechanical power developed by the motor is ............ (i) 20 W (iii) 500 W (ii) 980 W (iv) 200 W
The name plate of single phase induction motor has following data output 373W,230V, frequency 50Hz. Input current 2.9A and power factor is 0.71. Speed 1420 rpm What is efficiency of motor.
The rotor of a 3-phase, 60-Hz, 4-pole induction motor gets a total of 120kW through the air gap with a rotor frequency of 3Hz. a. What is the rotor speed (RPM)? b. What is the rotor copper loss (W)?
A value of magnetizing current in a 3-phase induction motor * gives power factor smaller .. larger smaller. .poor large . better O large...poor O
A four-pole induction motor drives a load at 2478 rpm. This is to be accomplished by using an electronic converter to convert a 400-V dc source into a set of three-phase ac voltages. Part A Find the frequency required for the ac voltages assuming that the slip is 4 percent. The load requires 2 hp. Express your answer to three significant figures and include the appropriate units. f= Submit Part B Value I = HA Request Answer Submit If the dc-to-ac converter has a power efficiency of 90 percent and the motor has a power efficiency of 80 percent, estimate the current taken from the dc source. Express your answer to three significant figures and include the appropriate units. HÅ Value Units Request Answer ? Units ?
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