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.