how to measure the inductance of an induction motor

Discussion in 'The Projects Forum' started by onlyvinod56, Oct 15, 2008.

  1. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    362
    1
    Hi
    i want to measure the losses in an induction motor. can u help me in determining the inductance of the motor.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Measure the resistance of one of the stator coils. Then lock the rotor and apply a low AC voltage, say 24Volts and measure the current through the coil. Then according to the magnitude of the current and its phase shift with the voltage determine the impedance of the coil. Finally, extract the inductance out of this impedance by using complex numbers.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    ∏There are meters for that purpose.

    Another method is to use a signal generator and fixed resistor. Sweep the frequency and use a meter to track voltage across the winding. It will be at a maximum at some frequency. That gives you the F term and the Xl term in the inductance formula: Xl = 2∏FL. Solve for L with a bit of algebra.
     
  4. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    Just a bit of a warning, inductance is dynamic in motors. This is because as the flux density is increased, the permeability will drop. If you need to model the motor for some control application, you may need to do locked rotor tests under varying current.

    Steve
     
  5. siddharth mittal

    Member

    Oct 14, 2008
    23
    0
    please tell how permeability falls due to increase in flux density?
     
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