Iron Loss Evaluation of an Ultrathin Electrical Steel Sheet for a High-speed Motor Stator Core Under PWM Excitation

It is well-known that iron loss in the stator core of a motor increases when the rotational speed of the motor increases. An eddy-current generated in the stator core is the cause of the increased iron loss. To decrease the eddy-current loss in the stator core, it is effective to reduce the thickness of the electrical steel sheet used for the stator core. We developed a 0.08-mm-thick ultrathin electrical steel sheet for the stator core of a high-speed motor. To demonstrate its effectiveness, we prepared two ring cores including one made of the 0.08-mm-thick ultrathin electrical steel sheet and another made of a 0.35-mm-thick electrical steel sheet. We compared the iron loss excited by a sinusoidal wave with the iron loss excited by a Pulse Width Modulation (PWM) wave using the two ring cores. In both specimens, the iron loss excited by the PWM wave was larger than the iron loss excited by the sinusoidal wave. Particularly in the specimen made of the 0.08-mm-thick ultrathin electrical steel sheet, the increasing rate of iron loss caused by an increase in the carrier frequency of the PWM wave was lower. In this paper, the effectiveness of a high-speed motor stator core made of a 0.08-mm-thick ultrathin electrical steel sheet is shown.