The Effect of the Three Level Neutral Point Clamped (NPC) Inverter on the Core Loss of a Synchronous Reluctance Machine (SynRM)

The effects of the three level inverter on the core losses of a SynRM are investigated particularly at the stator yoke and tooth. A comparative study on the effects of space vector pulse width modulated (SV-PWM) two and three level inverter on the iron/core loss are analyzed. A SynRM stator made of silicon steel, M36, 0.35 mm thickness is used. The machine was driven from a two and three level inverters and the current waveforms where used in the finite element model so as to capture the flux densities. The SynRM stator was then excited by these flux density waveforms obtained from the FE model. Tests were conducted at 30 Hz, 60 Hz and 180 Hz and there was an approximate 6 % reduction in core losses at 180 Hz under a three level inverter drive. The reduction in core losses were significant on the stator tooth than on the stator yoke. The use of a three level inverter will reduce the burden of the cooling system on the machine.