On-line estimation of stator resistance and mutual inductance of multiphase induction machines

Multiphase drives are receiving attention not only for medium and high power applications, but also for some low power applications, such as heavy electric vehicles. In the case of multiphase induction machines, the most widely adopted control technique is the field-oriented vector control, which provides high torque dynamics and can exploits all the degrees of freedom that this technology offers, but requires an adequate knowledge of the machine parameters. In this paper, a technique for the on-line estimation of the stator resistance and the magnetizing inductances is proposed. Under the assumption that the machine torque is produced by the fundamental component of the air-gap magnetic field, the proposed technique controls the higher harmonics in such a way to excite the machine and to estimate the unknown parameters. Experimental tests confirm the feasibility of the method described in the paper.