Extension to Multiple Coupled Circuit Modeling of Induction Machines to Include Variable Degrees of Saturation Effects

Multiple coupled circuit models (MCCM) of cage induction machines (CIMs), also called the winding function approach, is the most detailed and complete model used to analyze the performance of CIM especially under various faults. However, the inclusion of saturation effects to this model is still in the beginning stages. This paper extends the model to include variable degrees of saturation effects using an air gap function which incorporates saturation factor as a parameter. Simple exact analytic equations have been obtained to update time varying inductances used in the model and their derivatives versus rotor position. This eliminates the need for huge lookup tables, inexact analytic equations, and numerical differentiations which are common in MCCM. Also, this facilitates the introduction of the saturation factor to the model as a continuous variable. A novel technique has been introduced to locate the angular position of the air gap flux density, which is required with the air gap function. Results obtained from the simulation of a general purpose CIM is verified by the results obtained from the experiments and this demonstrates the efficiency of the extended model.