Test on basics

Electrical Engineering Electrical Machines
1

Terms and Definitions – Self Test 1
Questions

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Using the above diagram, answer questions 1 to 5:

  1. Which letter identifies the component that normally provides overcurrent protection for the
    motor branch circuit?
  2. Which letter identifies the component that normally provides overload protection for the
    motor branch circuit?
  3. When energized by the control circuit, which letter identifies the component that provides
    normal starting and stopping actions?
  4. Between which two letters is the control circuit power normally taken from?
  5. Which letter(s) identify devices that must be horsepower rated?
  6. A melting alloy type of thermal overload is called a:
    A. Solder-pot relay
    B. Dash-pot relay
    C. Thermal relay
    D. Bimetallic relay
  7. The part of a manual AC motor starter which senses motor overload current is the:
    A. High-limit switch
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    B. Solder-pot assembly
    C. Overload contact
    D. Heater element
  8. If automatic starting after a power failure represents a safety hazard for a motor drive, it
    should be equipped with:
    A. Low voltage release
    B. A flashing red light
    C. Low-voltage protection
    D. A warning sign
  9. An overload relay that uses a strip of dissimilar metals is called a _______ relay
    A. Melting alloy
    B. Thermistor
    C. Solder pot
    D. Bimetallic
  10. Referring to the drawing, assuming that fuse C is blown, which pair of points will result in a
    reading of zero volts when the voltmeter is connected across them?

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  1. To connect a motor solely for jogging operation, the control circuit will:
    A. Use holding contacts
    B. Connect holding contacts in series with the start button
    C. Connect holding contacts in parallel with the start button
    D. Not use holding contacts
  2. Timed relays are the best method to provide plugging for a motor. True or false?
    146 Chad Flinn and Aaron Lee
  3. The electrical interlocks in a reversing magnetic starter are:
    A. Controlled by the timing relays necessary for circuit operation
    B. In parallel with the forward and reverse pushbuttons
    C. Normally closed contacts
    D. Normally open contacts
  4. Overload protection for motors is achieved by connecting:
    A. Thermal sensing elements in series with the motor
    B. A reset relay in series with the motor
    C. Cartridge fuses in series with the motor
    D. A set of N.C contacts in series with the motor
  5. With a three-wire control circuit, when power is restored after a low voltage situation:
    A. An operator must restart the motor
    B. The motor will polyphase
    C. The motor will automatically restart
    D. The motor will automatically restart after a time delay
    Answers
  6. B
  7. D
  8. C
  9. B and C
  10. A and C
  11. A
  12. D
  13. C
  14. A
  15. 3 and 6
  16. D
  17. False
  18. C
  19. A
  20. A
Reference

Basic Motor Control by Aaron Lee and Chad Flinn is used under a CC BY 4.0 Licence.