Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Chapter 55, Problem 1SQ
To determine
Explain the operating principle for all three-phase motors.
Expert Solution & Answer
Explanation of Solution
Discussion:
The three-phase AC motors work on the principle of rotating magnetic field (RMF). When the three-phase supply is connected to stator of the motor, the three-phase currents induce the three flux waves. The fluxes interact with each other and produce the RMF. The speed of the RMF is a synchronous speed.
The synchronous speed of RMF depends on the number of poles per phase and the applied voltage’s frequency. The electromotive force (EMF) is induced in the rotor conductors due to the RMF. The induced EMF on the rotor leads to the flow of current in the rotor conductors, and subsequently rotor torque is produced. The rotor rotates in the direction of RMF due to the rotor torque.
Conclusion:
Thus, the operating principle of all three-phase motors is explained.
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What are the three basic types of three-phase motors?
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
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Chapter 55 Solutions
Electric Motor Control
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- What are the principle characteristics of DC series motor and DC compound motor, and what are its uses? Explain the Difference between Single Phase & Three Phase transformers with a Comparison Chart. What conditions are necessary for paralleling two synchronous generators?arrow_forwardA-1)- a- Which of the following is/are a general class of single-phase split-phase motor? a resistance-start induction-run b capacitor-start induction -run c) capacitor-start capacitor-run d) all of the aboveb-The single-phase split-phase motor operates on the principle of a rotating magnetic field. a) true b) false c- The voltages in a 2-phase power system are_______ degrees out of phase. a) 90 b) 120 c) 180 d) none of the above d-The voltages in a 3-phase power system are______ degrees out of phase. a) 90 b) 120 c) 180 d) none of the above e- Which of the two stator windings used on single-phase split-phase motors is made up of smaller wire? a) start winding b) run winding c) either "a" or "b" d) neither "a" nor "b"arrow_forwardQ3) I. What' s the effect of The auxiliary winding of split - phase induction motor when it becomes short circuit ?arrow_forward
- 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 abovearrow_forwardWhy do we need to have brushes in a squirrel-cage rotor type induction motor? (short answer)arrow_forwardExample -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?arrow_forward
- B: Compare between split-phase and the shaded pole motors.arrow_forwardA 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?arrow_forwardA 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)arrow_forward
- A Switched reluctance motor has a phase sequence of A-B-C while rotating clockwise. Phase sequence while rotating anti clockwise is .. O C-A-B O B-C-A O A-B-C O A-C-Barrow_forward• Q5/ in a DC motor. List and describe the types of losses that occurarrow_forwarddiscuss how the dc motor is used in washing machinearrow_forward
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