Investigation on Stator Mutual Inductance Factor used for Induction Machine Control

-0.5 is commonly used as stator mutual inductance factor for induction motor control. However, -0.5 is only valid if magnetomotive force is sine wave. Due to the definition of inductance calculation, only one phase should be excited with current; hence, the magnetomotive force can never be a sine wave when calculating the inductance, even number of slots per pole per phase is infinitely large. It is known that this value is influenced by winding topology; however, until now, the analytical expression of this factor has not been found yet. Moreover, the value of this factor cannot be easily obtained via experiments, especially for squirrel cage induction motor. Hence, the contribution of this work is, the analytical expression for calculating this factor is derived and exhibited in detail. Both single-layer and double-layer machine with short-pitched winding are covered. Finite element analysis is performed to validate the discovery. Experiment has been done.