Motors_Generators

Card Set Information

Author:
jasonstone808
ID:
103560
Filename:
Motors_Generators
Updated:
2011-09-22 09:08:55
Tags:
GFES Motors Generators Electrical theory
Folders:

Description:
GFES. Motors and Generators and Electrical Theory.
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  1. If a locked rotor occurs on an operating motor-driven pump, motor amps will... (increase or decrease?) Why?
    ...increase due to the decreased rotor speed.

    An instantaneous increase in pump current is required to supply the demanded torque. With torque demand at maximum current demand will be at maximum.
  2. A cooling water pump is being driven by an AC induction motor. Describe how and why pump motor current will change if the pump shaft seizes...
    Current increases.

    When the rotor is seized it stops turning and the motor no longer has the CEMF to limit the current in the armature and the current goes to maximum to try to turn the motor to turn the pump.
  3. Continuous operation of a motor at rated load with a loss of required cooling to the motor windings will eventually result in...
    ...breakdown of the motor insulation and electrical grounds.

    Operating without required cooling of the motor will result in excessive heat being generated by I2R heating losses.
  4. Which one of the following will provide motor protection against electrical damage caused by gradual bearing degradation?
    A. Thermal overload device
    B. Underfrequency relay
    C. Undervoltage device
    D. Overcurrent trip relay
    A. Thermal overload device
    (this multiple choice question has been scrambled)
  5. If an AC generator is operating with a Power Factor of 1.0, is it seen as resistive or reactive?
    A Power Factor of 1.0 indicates a resistive circuit
  6. If an AC generator is operating with a Power Factor of 0.23, is it seen as resistive or reactive?
    A Power Factor of < 1.0, such as 0.23 (or 23%) indicates a reactive circuit

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