I. INTRODUCTION
A lot of induction motors, in which electrical steel is used as stator core, are driven by PWM inverter. However, according to the domestic and international standards, electrical steel property is decided by being measured in sinusoidal wave source (linear amplifier) excitation [1, 2]. PWM inverter has a lot of harmonics components in its output voltage, though sinusoidal wave source contains no harmonics. The comparison between sinusoidal source excitation and PWM inverter drive is a very important problem for the iron loss evaluation.