The Effect of Two- and Three-Level Inverters on the Core Loss of a Synchronous Reluctance Machine (SynRM)

The paper shows the reduction of core losses by using a three-level inverter over a two-level inverter for the same dc-bus voltage and switching frequency. A synchronous reluctance machine stator-core toroid was used in the analysis. Hence, the analysis is realistic as it accounts for mechanical effects through the stator core, and the distorted supply of the line-to-line inverter voltage supplies. The paper also shows the limitations of using finite element-derived excitation; hence, the toroid was directly supplied by the inverter. The reduction of core losses by use of a three-level inverter is significant at very high flux densities and frequencies; approximately 60% lower core losses. Therefore, it can reduce the cooling burden especially in the hard to cool teeth, increase the service life, and allow increased output. The latter is because the output of the three-level fundamental voltage is higher for the same dc-bus and switching frequency at lower machine losses.