Hi
i want to measure the losses in an induction motor. can u help me in determining the inductance of the motor.

 

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.

 

∏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.

 

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

 

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

please tell how permeability falls due to increase in flux density?