PWM Influence on the Iron Losses and Characteristics of a Slotless Permanent-Magnet Motor With SiFe and NiFe Stator Cores

This paper investigates the influence of switching frequency and modulation index combined with welding on the iron losses in thin silicon–iron and nickel–iron lamination sheets of a small slotless permanent-magnet synchronous machine (PMSM). First, measurements are conducted on welded and nonwelded stator ring cores for switching frequencies between 1 and 20 kHz and modulation indexes of 0.4, 0.7, and 0.9, keeping constant fundamental flux density peak values. This is possible by changing the dc-link voltage of the inverter. The obtained measurement data are afterward used in finite-element method simulations to investigate the inverter influence on the performance of the PMSM.