Wound Rotor Motor

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Author:
johnbowens
ID:
119526
Filename:
Wound Rotor Motor
Updated:
2012-01-09 21:39:54
Tags:
wound rotor motors ibew jatc
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Description:
Wound Rotor Motors ISBN:978-0-8269-1982-3
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  1. Wound Rotors are especially useful for what reason? Motors Second Edition 2010, PP 118 (NC set: wound rotor motor)
    They are able to deliver high starting torque without overloading the electrical supply system.
  2. What is the difference between a squirrel cage motor and a wound rotor motor? Motors Second Edition 2010, PP 118 (NC set: wound rotor motor)
    The conductor bars are replaced with coils of wire.
  3. The windings in a wound-rotor motor are wye or delta? Motors Second Edition 2010 PP 118 (NC set: wound rotor motor)
    Either, and dual or single voltage.
  4. The Rotor of a wound-rotor motor is different from a squirrel cage motor how? Motors Second Edition 2010 PP 119 (NC set: wound rotor motor)
    The conducting bars are coils of wire, there are 3 slip rings, and an external resistance bank.
  5. Wound-rotor motors may be delta or wye wound, to match what? Motors Second Edition 2010 PP 119 (NC set: wound rotor motor)
    The stator: the rotor is wound to match their stator in this type of motor.
  6. The rotor windings in a wound-rotor motor are marked what? Motors Second Edition 2010 PP 119 (NC set: wound rotor motor)
    M1, M2, and M3.
  7. External resistors are used to limit what? Motors Second Edition 2010 PP 118 (NC set: wound rotor motor)
    Starting current and to create a more resistive circuit with more starting torque.
  8. Brush material is usually composed of what, for high and low voltage machines? Motors Second Edition 2010 PP 120 (NC set: wound rotor motor)
    • High voltage: carbon and graphite
    • Low voltage: metallic powder and graphite
    • Note: graphite functions as a lubricant
  9. The resistors used with the rotor in a wound-rotor motor are often referred to as what? Motors Second Edition 2010 PP 120 (NC set: wound rotor motor)
    Secondary resistors, because the rotor is the secondary of the motor.
  10. How much rotor current is carried by the resistors in a wound-rotor motor? Motors Second Edition 2010 PP 121 (NC set: wound rotor motor)
    All of the current is carried by this in a wound rotor motor.
  11. As the wound-rotor motor speed is reduced the frequency is raised, this affects an ammeter how? Motors Second Edition 2010 PP 121 (NC set: wound rotor motor)
    The ammeter operates at 60 HZ and will not operate at higher HZ and lower motor speeds effectively.
  12. A starter starts a wound-rotor motor with how much resistance in the circuit? Motors Second Edition 2010 PP 122 (NC set: wound rotor motor)

    When the motor reaches full speed, what happens to the resistance? Motors Second Edition 2010 PP 122 (NC set: wound rotor motor)
    Full resistance

    It is switched out and the rotor windings are shorted in a wound-rotor motor. (Thus operating like a shorting ring in a squirrel cage induction motor.)
  13. The resistors in a wound-rotor motor starter are designed for continuous operation? Motors Second Edition 2010 PP 122 (NC set: wound rotor motor)

    What must be used in order to allow continuous operation of resistors after starting in a wound-rotor motor? Motors Second Edition 2010 PP 122 (NC set: wound rotor motor)
    These in a wound-rotor motor are not designed for continuous operation.

    • A regulator, must be used in order to allow this i a wound rotor motor.
  14. In a wound rotor motor, the starting torque decreases as the frequency decreases and the speed of the rotor increases, thereby reducing current and induction in the rotor and allowing resistance to be removed manually or automatically how? Motors Second Edition 2010 PP 122 (NC set: wound rotor motor)
    manually with a rheostat (a series resistor limiting voltage) or automatically with a controller and.
  15. For each step in acceleration in a wound-rotor motor, what happens to current and frequency in tcontactorshe rotor? Motors Second Edition 2010 PP 123 (NC set: wound rotor motor)

    Why?
    Current and Frequency in the rotor decrease as the rotor starts turning during startup. (summary motors PP 128)
  16. When the speed of the wound-rotor motor rotor is reduced, what increases resulting in more current induced into the windings of the rotor? Motors Second Edition 2010 PP 125 (NC set: wound rotor motor)
    Slip occurs as the speed of a wound-rotor motor rotor is reduced, resulting in more of this.
  17. when a wound-rotor motor operates at a lower speed, what happens to normal ventilation and therefore speed? Motors Second Edition 2010 PP 125 (NC set: wound rotor motor)
    The normal ventilation is reduced and therefore the speed is usually reduced no more than 50 percent.
  18. The most common type of 3 phase motor is what? Motors Second Edition 2010 PP 385 & Electrical Field reference hand book NEC 2008 (NC set: wound rotor motor)
    Squirrel cage induction type
  19. In a wound-rotor motor, because some of the resistors in the rotor circuit are shunted, the resistance in the rotor circuit is what? What happens to rotor current? Motors Second Edition 2010 PP 124 (NC set: wound rotor motor)
    Resistance in the rotor decreases and thereby the rotor current increases. Shunted means parallel.
  20. Wound-rotor motor regulators are high or low wattage resistors? Meaning what? Motors Second Edition 2010 PP 125 (NC set: wound rotor motor)
    High wattage, meaning they may remain in the circuit continuously to maintain speed. Versus a starter which cannot due to low wattage resistors.
  21. Three common types of wound-rotor motor regulators are? Motors Second Edition 2010 PP 125 (NC set: wound rotor motor)
    Drum switches, three pole rheostats, and silicone controlled rectifiers.
  22. Of the three common wound-rotor motor regulator types, which one is used the least? Motors Second Edition 2010 PP 125 (NC set: wound rotor motor)
    Silicon-controlled Rectifiers (SCR's). Because they are only used in applications that require continuous speed variations.

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