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AC induction motor,i use a strong clamper to lock the motor shaft

  1. Sep 24, 2009 #1
    I have a AC induction motor,i use a strong clamper to lock the motor shaft.Then i switch on the power supply.?
    So,i wanna ask is there the motor will become short circuit?
    Can i know what is the cause for this malfunction?Is that the motor stator burn out or they still got other reason causing this?
     
  2. jcsd
  3. Sep 24, 2009 #2
    Re: motor

    Quick question on what you are trying to do.... Are you trying to test the characteristics of a motor, debug a motor, or are you trying to figure out why the motor cannot provide an adequate amount of torque at a radial velocity of zero?

    As for whether or not it will look like a short circuit, and the answer is no. There's the stator and rotor impedances to take into account.
     
  4. Sep 24, 2009 #3
    Re: motor

    No. It will become an electric heater.

    I don't understand this question. Locking the rotor with a clamp is not a malfunction.

    The motor will continue to heat until the overload switches it off. When the motor cools down the overload will switch back on and the cycle will repeat.
     
  5. Sep 24, 2009 #4
    Re: motor

    Do you happen to know why?
     
  6. Sep 24, 2009 #5
    Re: motor

    Ya.I want to test the characteristics of the motor.I want too find out if accidently the motor rotor is stuck but the motor power supply are still switch on, so will the motor burn? And what is the causes to this?
    By the way,may i know what is the motor overload switch?
     
  7. Sep 24, 2009 #6
    Re: motor

    It's a thermal overload which is located in close proximity to the windings and field core. It simply switches the main winding on and off with rise and fall of temperature.
     
  8. Sep 24, 2009 #7
    Re: motor

    This mean every motor have this thermal overload switch,and how this thermal overload switch operate?
     
  9. Sep 24, 2009 #8
    Re: motor

    It's called a lock rotor test. If the thermal overload is functioning correctly then the motor will become very hot, but not hot enough to cause damage. However, a locked rotor is not a normal condition and the motor should not be purposely operated that way.
     
  10. Sep 24, 2009 #9
    Re: motor

    Well, all I can say is that every motor my company manufactured had an overload. We manufactured fractional hp motors between about 1/5 hp to 1 hp.

    Our motors were required to have an overload for UL certification.
     
    Last edited: Sep 24, 2009
  11. Sep 24, 2009 #10
    Re: motor

    Thank,Sir...But if we despite the overload switch.We just supply the normal power to the motor and with the rotor locked.So ijust wanna know will the motor burn out or it still can operate like before after we remove the locked?
     
  12. Sep 24, 2009 #11
    Re: motor

    If you operate a locked rotor motor without an overload then the enamel on the motor windings will start to burn. It smells bad. :) This would be a fire hazard. The windings would eventually short out and trip the breaker, hopefully before it starts a fire.

    The amount of time you can operate a motor with locked rotor varies depending on the motor design.
     
    Last edited: Sep 24, 2009
  13. Sep 24, 2009 #12
    Re: motor

    Thanks Sir...But a motor is build up with coil same as transformer.So if we let the transformer switch on with no load connect to it,is it will burn also?
     
  14. Sep 24, 2009 #13
    Re: motor

    No. A motor is similar but not the same as a transformer. There is an air gap between the stator and rotor. A locked rotor motor is more comparable to a transformer with its output shorted. If not fused then the transformer would also burn.
     
  15. Sep 24, 2009 #14
    Re: motor

    Thanks Sir..Thanks for the info...=)
     
  16. Sep 24, 2009 #15
    Re: motor

    You're welcome. Glad I could help.
     
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