The paper investigates maximum possible torque improvement in a two-pole surface permanent magnet synchronous machine (PMSM) with a reduced magnet span, which causes production of highly nonsinusoidal back-EMF. It contains a high third and fifth harmonics, which can be used for the torque enhancement, using stator current harmonic injection. Optimal magnet span is studied first and it is shown that with such a value the machine would be able to develop an insignificantly lower maximum torque than with the full magnet span. Next, field-oriented control (FOC) algorithm, which considers all non-fundamental EMF components lower than the machine phase number, is devised. Using maximum-torque per Ampere (MTPA) principles, optimal ratios between fundamental and all other injected components are calculated and then used in the drive control. The output torque can be in this way increased up to 45% with respect to the one obtainable with fundamental current only. Alternatively, for the same load torque, stator current RMS value can be reduced by 45%. Last but not least, a method for position sensor fault mitigation is introduced. It is based on the alternative use of a back-EMF harmonic for rotor position estimation, instead of the torque enhancement. Experimental verification is provided throughout for all the relevant aspects.

The version presented here may differ from the published version or from the version of the record. Please see the repository URL above for details on accessing the published version and note that access may require a subscription.

This paper investigates multiphase drives in which winding configuration (symmetrical or asymmetrical) can be easily obtained by only rearranging voltage source inverter (VSI) power supply cables at the machine's terminal box. The type of the machines where this is possible is identified and the examples of reconfiguration are given and explained. Following from the examples (for nine-and fifteen-phase cases), a general reconfiguration algorithm is introduced. As shown, changing asymmetrical to symmetrical winding configuration (and vice versa) means that just another mimic diagram needs to be placed over the existing one on the machine's terminal box. Possible reconfigurations of a six-phase machine, which do not follow the same pattern, are also addressed. Differences caused by different winding configuration are identified and experimentally confirmed using a nine-phase surface mounted permanent magnet synchronous machine (PMSM) and a nine-phase induction machine (IM).

No abstract

No abstract