# 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?