Extended back EMF model for PM synchronous machines with different inductances in d- and q-axis

This paper discusses a reluctance-dependent back electromotive force (EMF) model for encoderless vector driven permanent magnet synchronous machines (PMSM) compared to well known, non reluctance-dependent back EMF models. Established PMSM could have considerable varieties in direct and quadrature inductances. So it makes sense to consider this behaviour in an extended back EMF model. On closer examination it will turn out that a reluctance dependent EMF model has a better behaviour at low speed as the standard model. Also the derivation of the extended model will be illustrated. Furthermore some simulation results and practical measurements will be discussed.