Quiz 5

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School

Defense Acquisition University *

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Course

EET390

Subject

Mechanical Engineering

Date

Dec 6, 2023

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docx

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2

Uploaded by charleshaskett on coursehero.com

1. Excessive starting is a prime case of motor failures. True 2. There are no slip rings or any voltage supplied to the rotor of an induction motor. True 3. Direct current motors can normally operate directly from the power supplied by the electric utility system.Direct current motors can normally operate directly from the power supplied by the electric utility system. False 4. Voltage unbalance is the unbalance that occurs when the voltages at the 3-phase motor terminals are not equal 5. A three-phase synchronous motor can produce a leading power factor. True 6. When a load is applied to a 3-phase squirrel cage-motor induction motor, the rotor speed will decrease slightly 7. The purpose of a commutator on a DC motor is to maintain the proper direction of current flow in the armature conductors 8. A DC shunt motor should never be operated without a load 9. The armature of a DC motor acts like a generator in producing counter electromotive fore (CEMF). True 10. When you vary the armature voltage the motor produces full torque but the speed is varied. True 11. The _________ nature of induction motor operation comes from the slip between the rotational speed of the stator field and somewhat slower speed of the rotor. Asynchronous 12. A voltage unbalance can magnify the percent current unbalance in the stator windings of a 3-phase motor by as much as 6 to 10 times the percent voltage unbalance. True 13. On a 3-phase motor, the stator windings are arranged to create a rotating magnetic field
14. The motor energy losses due to the resistance of the windings are known as the core losses 15. The synchronous speed of a 2-pole, 60-hertz AC motor is 3600-rpm 16. If one phase to a 3-phase motor is lost while operating, the motor may continue to rotate. True 17. ________ torque is the torque produced by a motor functioning at rated speed and horsepower. Full load 18. A multimeter is normally used to test the insulation integrity of motor windings. False 19. One of the features of a DC motor is that its speed can be easily controlled. True 20. Like 3-phase induction motors, 3-phase synchronous motors are normally self-starting. False
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Related Questions
Problem 5 1. Where and why is a centrifugal switch used in a split-phase motor? 2. Why and where is a capacitor used in the single-phase AC motor? 3. What type of motor would you select to perform each of the following jobs? (a) Electric drill: (b) Refrigerator: (c) Hair driers and desk fans: (d) Air Conditioner Fan: (e) XY plotters and printers: (f) Electric clock:
In dc. motor, the undirectional torque is produced with the help of *
AHO LUI 3. True or false? A magnetic field opposing the stator's magnetic field is produced in a motor's rotor by a process called induced magnetism.
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