RATING: MOTOR CONTROLER

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pascual
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3551
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RATING: MOTOR CONTROLER
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2009-12-27 16:13:22
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  1. What Naval Ship's Technical Manual (NSTM) deals with electric motors and motor controllers?
    NSTM302.
  2. How does a magnetic motor controller function?
    The contacts are opened by electromechanical devices.
  3. What is the most common type of motor controller found on Gas Turbine vessels? Magnetic across-the-line type.
  4. What is a master switch?
    A device that controls the electric operation of a motor controller.
  5. Float, limit, and pressure switches are all examples of what type of master switches?
    Automatic master switches.
  6. Multi contact switches are classified in what manner? By the number of poles and the number of
    throws.
  7. Accurate snap-acting type switches are commonly known by what name? Microswitches.
  8. What are 8 types of microswitches?
    Lever, leaf, pin-plunger, roller lever, roller leaf, overtravel plunger, panel-mount plunger, panel-mount roller plunger.
  9. A microswitch with a leaf roller is used for what application?
    Low-force, slow moving cams or slides.
  10. What are two basic methods used to check a switch?
    An ohmmeter or a voltmeter.
  11. The speed of a two-speed AC induction motor is controlled by what?
    By shifting from one set of windings to another.
  12. What does the acronym LVP stand for?
    Low voltage protection.
  13. What type of controller uses a closed-transition compensator which keeps the motor connected to the supply line during the entire transition period?
    Autotransformer controller.
  14. What happens to electrical equipment with LVP installed upon a loss of supply power? You must manually restart the controller.
  15. How does a LVR controller function?
    When supply voltage is reduced or lost altogether the controller disconnects the motor from the supply, when power is returned it restarts.
  16. Most small manual across-the-line controllers are equipped with what type of voltage protection?
    LVRE - Low voltage release effect.
  17. Nearly all shipboard motor controllers are protected from excessive current by?
    Overload relays
  18. What are the two types of overload relays installed on shipboard controllers?
    Thermal and Magnetic.
  19. What are the four types of thermal overload relays?
    Solder-pot, Bimetal, Single-metal, and Induction.
  20. What type of thermal overload relay uses a heat-sensitive element connecting a cylinder to a hollow tube?
    Solder-pot type.
  21. When adjusting a thermal overload relay a coarse adjustment is achieved by?
    Changing the heater element.
  22. How does a Bimetal type overload relay function?
    When heated the strip or coil deflects because one metal expands more than the other. The deflection causes the overload relay to open.
  23. What type of thermal overload relay can be used for AC or DC?
    Induction type.
  24. An overload relay that has a coil connected in series with the motor circuit and a tripping armature or plunger is known as?
    A Magnetic overload relay.
  25. Controllers are protected from short circuits by?
    A circuit breaker in the power supply system.
  26. How is short circuit protection provided for in control circuits?
    By fuses in the controller enclosure.
  27. After a thermal overload relay has tripped, the relay must be allowed to cool for what duration of time before resetting the relay?
    1 minute or longer.
  28. What are three types of overload relay resets?
    Manual, automatic, and electrical.
  29. A chattering controller usually is attributed to what?
    Dirty relay contacts.
  30. What provides uninterruptable power to the 60 Hz ship's service power system upon a loss of power?
    Battery backup systems.
  31. What system is known as the uninterruptable power system?
    The UPS system.
  32. Propulsion electronics operate at what power range?
    115/120 Volt range.
  33. The batteries in the UPS system generate what type of power?
    Low-voltage DC power.
  34. What type of batteries are used in the UPS system?
    Acid-lead Wet cell type.
  35. What type of controller uses an electromechanical device to open and close contacts?
    A magnetic controller.
  36. A resistor controller is only used for what type of applications?
    DC only.
  37. What type of controller starts the motor at reduced voltage through an auto-transformer?
    A compensator controller.
  38. Name two types of compensator controllers?
    Open transition and closed transition.
  39. How are controllers classified?
    As either manual or magnetic.
  40. What is the most common type of AC controller?
    Across-line type.
  41. What device protects the motor from overheating by excessive current?
    An overload relay.
  42. Overload relays are classified into what two types?
    Magnetic and thermal.
  43. What type of overload relay has a coil connected in series with the motor load circuit and a tripping armature or plunger?
    Magnetic type
  44. Name two types of magnetic overload relays?
    Instantaneous and time-delay type.
  45. What is the most common type of time-delay magnetic overload relay?
    An oil dashpot with a piston attached to the tripping armature.
  46. What determines the speed of operation on a time-delay magnetic overload relay? he size of the hole in the piston.
  47. How is the tripping current adjusted in both the instantaneous and time-delay magnetic overload relays?
    By changing the distance between the series coil and the tripping armature.
  48. What effect does ambient temperature have on magnetic overload relay operation?
    None.
  49. What are four types of thermal overload relays?
    Solder pot, bimetal, single metal and induction.
  50. What thermal overload is constructed of a cylinder inside a hollow tube held together by solder?
    Solder pot type.
  51. What type of thermal overload can only be used for AC applications?
    Induction type.
  52. The copper tube within an induction type thermal overload relay serves what function?
    Acts as the short circuited secondary of a transformer and is heated by the current induced in it.
  53. The heat-sensitive element within the induction type overload relay is of what design?
    Bimetal strip or coil.
  54. How is a rough adjustment made on a thermal overload relay?
    By changing the heater element.
  55. What are three methods of resetting a tripped overload relay?
    Manual (hand), automatic and electric reset.
  56. What is the most common type of reset method used on overload relays?
    Manual or hand reset.
  57. Where is the hand reset normally located?
    In the controller enclosure.
  58. What type of overload relay reset device is reset by spring tension or gravity?
    Automatic reset device.
  59. When is full field protection required?
    It is required in controllers for DC motors in which a shunt field rheostat or resistor is used to weaken the motor field and obtain motor operation at speeds in excess of 150 percent of the rated field current.
  60. What is a solenoid?
    A control device that uses electromagnetism to convert electrical energy into mechanical motion.
  61. What is the inner core of the solenoid constructed of?
    Soft-iron.
  62. What energizes the solenoid?
    A switch or relay.
  63. The solenoid's effective strength within the magnetic field and the plunger will vary based on what variable?
    The distance between the plunger and the core.
  64. What links the solenoid to the relay?
    Electrical wiring.
  65. What is the difference between a solenoid and a relay?
    The relay does not have a movable core (plunger).
  66. Power relays are commonly called what?
    Contactors.
  67. What does the term "cone and crater" mean when associated with a relay?
    A detrimental effect caused by current flowing in one direction through the relay.
  68. What is the advantage of a relay equipped with ball-shaped contacts?
    Dust or other substances are not as readily deposited on a ball-shaped surface.
  69. Which type of relay is used to control low power common circuits?
    Control relay.
  70. Anchor windlasses use what form of circuit protection to prevent excessive motor overloading?
    Jamming or step-back protection.
  71. Electrical brakes are normally operated with what type of driver?
    solenoid or motor.
  72. What type of tool is used to clean ball-shaped contacts?
    burnishing tool.
  73. After using a burnishing tool it should be immediately cleaned with what?
    Alcohol.
  74. What special tool is used to straighten bent contacts in a relay?
    point bender.

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