What Is "stator magnetizing inductance"

Submitted by Duco Pulle on Fri, 04/27/2012 - 03:41.

Okay lets start from first principles: inductance (L) is the ratio of flux divided by current( or voltage divided by rate of current change). So if you apply a current to the phase winding then a flux will result. Of the flux that a winding 'sees' part of this is leakage flux, which is the component of the flux that does not cross the airgap to the rotor, IE it is only seen by the stator winding. That flux component divided by the applied current is the leakage inductance. The other flux component that crosses the airgap (twice of course) is called magnetizing flux from its use in induction motors to induce current flow and a resulting magnetic field in the nonmagnetic but conducting rotor. In PM machines, this flux component is small compared to the leakage flux as it passes through air and magnets (which are also seen as air), so it has a larger path through air than the leakage flux which sits nears the flux concentrating slots.
The flux that crosses the air gap divided by the excitation current is the magnetizing inductance. The sum of magnetizing inductance and leakage inductance is the stator inductance (which is half the terminal inductance in a wye connected motor) see equation 6.2 of our book. Indeed measuring the magnetizing component separate from the stator inductance as a whole is difficult, finite element approach is then the way to go, but it is not needed for motor simulation as the total inductance is required in this case. Hope this helps, -Duco