Self Test on Motor Starters and Contactors

Electrical Engineering Electrical Machines
1

Questions

  1. The minimum number of control circuit conductors to a stop/forward/reverse pushbutton
    station that provides low-voltage protection for a three-phase reversible motor is:
    A. 2 wires
    B. 3 wires
    C. 4 wires
    D. 6 wires
  2. Which of the following type of motor starter does not normally provide running protection
    for the motor?
    A. A magnetic starter
    148 Chad Flinn and Aaron Lee
    B. A pushbutton starter
    C. A toggle-switch starter
    D. A drum-switch controller
  3. If the circuit in the drawing was operating normally and an overload occurred, then
    image
    image881×431 11.8 KB

    A. Both lights would come on
    B. The green light would come on, and the red light would go out
    C. Both lights would go out
    D. The red light would come on, and the green light would go out
  4. With a three-wire control circuit, when power is restored after a low voltage situation:
    A. The motor will automatically restart after a time delay
    B. The motor will automatically restart
    C. An operator must restart the motor
    D. The motor will polyphase
  5. A melting alloy type of thermal overload is called a:
    A. Solder-pot relay
    B. Thermal relay
    C. Bimetallic relay
    D. Dash-pot relay
  6. A starter rated at 10HP, 600 V, if used on a 120V motor would most likely be rated at:
    A. 2 HP
    B. 3 HP
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    C. 10 HP
    D. 2.5 HP
  7. A N.C.T.C contact will be open immediately after the coil is de-energized. True or false?
  8. An overload relay that uses a strip of dissimilar metals is called a _______ relay
    A. Thermistor
    B. Melting alloy
    C. Solder pot
    D. Bimetallic
  9. A shading coil is not required for a DC voltage coil. True or false?
  10. Overload protection for motors is achieved by connecting:
    A. A set of N.C contacts in series with the motor
    B. Thermal sensing elements in series with the motor
    C. Cartridge fuses in series with the motor
    D. A reset relay in series with the motor
  11. The part of a manual AC motor starter which senses motor overload current is the:
    A. Overload contact
    B. Solder-pot assembly
    C. Heater element
    D. High-limit switch
  12. The essential difference between a magnetic motor starter and a magnetic contactor is that the
    contactor does not contain:
    A. Shading coils
    B. Holding contacts
    C. Overload relay protection
    D. Horsepower-rated contacts
  13. The rotation of an AC three-phase induction motor may be reversed by interchanging:
    A. The control circuit
    B. The forward/reverse interlocks
    C. The forward reverse coils
    D. Any two power lines
  14. If an AC magnetic contactor with a 480V coil was energized with 120V, then most likely the:
    A. Overload relay would trip
    B. Contactor would not pick up
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    C. Control circuit fuses would blow
    D. Coil would overheat during normal operation
  15. In a control schematic, a dotted line between two coils generally means that the two coils:
    A. Are operated together
    B. Are mechanically interlocked
    C. Are electrically interlocked
    D. Have a common set of contacts
  16. During normal operation, a loud chattering noise is heard from the enclosure of an AC
    magnetic starter. What is the most likely cause?
    A. Broken shading coil
    B. Open in the seal-in circuit
    C. Rust on pole faces
    D. Power contact is not making good contact due to poor pressure
  17. The purpose of electrical interlocking in a three-phase reversing AC magnetic motor starter is
    to:
    A. Ensure that the forward direction of rotation is selected first
    B. Allow both coils to be energized together
    C. Prevent both coils from being energized simultaneously
    D. Maintain the coil circuit after the stop button is released
  18. A double-contact pushbutton is illustrated below. When connected as a start button in the
    control circuit of a magnetic starter, which pair of terminals are normally used
    image
  19. A time-delay relay includes both timed and instantaneous contacts. True or false?
  20. Fill in the missing words. The electrical interlocks on a reversing starter are normally
    _______ contacts
  21. A N.O.T.O contact will be closed while the coil of the relay is energized. True or false?
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  22. A N.C.T.O designation refers to an off-delay timer. True or false?
  23. The electrical interlocks in a reversing magnetic starter are:
    A. Normally closed contacts
    B. Normally open contacts
    C. In parallel with the forward and reverse pushbuttons
    D. Controlled by the timing relays necessary for circuit operation
    Answers
  24. D
  25. C
  26. D
  27. C
  28. A
  29. A
  30. False
  31. D
  32. True
  33. B
  34. C
  35. C
  36. D
  37. B
  38. B
  39. A
  40. C
  41. 3 and 4
  42. True
  43. Closed
  44. True
  45. False
  46. A
Reference

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