A simple circuit-oriented model for predicting six-phase induction machine performances

The paper deals with a six phase induction motor (6PIM) design for 42 V embedded application, in particular, for an electrical power steering (EPS). This motor with symmetrical 60 degrees displacement windings allows to have more reliability in automotive applications, such as steering by wire. In fact with a failure of one or more phases of one of the two three phase windings the motor is able to run as an usual three phase machine. The paper presents a simple circuit-oriented method to simulate a six-phase squirrel-cage induction machine (6PIM) in order to predict its performances. This method can be applied for different types of induction machines (one-phase, three-phase, six-phase and n-phase induction machines) and it consists in the elaboration of an electric equivalent circuit obtained from minimal dimensional knowledge of stator and rotor parts of the machine under study. It takes into account only the magnetic circuit dimensions and the airgap length. A six-phase squirrel-cage induction machine of 0.09 kW, 17 V, 50 Hz, 2-poles is used for the experimental set-up. The magnetic structure available by a standard three phase induction machine has been redesigned for getting the six phase one using a software devoted to the electromagnetic design and analysis of three phase induction machines. The finite element method associated to an induction machine non linear model has been used too with a complete description of stator and rotor cores using the iron non-linear characteristic for the final verification. The simulation results given by the circuit-oriented and the non linear modeling methods are compared with the experimental results for the classical torque-speed, current-speed and torque-current characteristics