In this research, it is observed that the iron loss on a star-connection is larger than that on a delta-connection under three phase PWM inverter excitation. Although some investigations by using three phase Pulse-Width-Modulation (PWM) inverter are performed until now[1-2], the investigation which paid its attention to difference of connecting method is not performed. Therefore, in order to clarify the influence by the difference in connecting method, the evaluation of iron loss by using three rings with three phase PWM excitation is carried out in this paper.