To reduce core loss of an electrical motor, lower iron loss magnetic materials than conventional electrical steel are selected for the motor core evaluation, where the selected ones are GO (grain-oriented) steel, amorphous steel, and nanocrystal material. They are applied to the electrical motor of IPM-SM (interior permanent magnet synchronous motor) and manufactured as GO motor, amorphous motor, and nanocrystal motor. As for GO motor, since GO steel has strong magnetic anisotropy, GO steel is divided into some pieces, and they are arranged so as that the main magnetic flux follows the easy magnetization direction of GO steel. The motor core loss is measured in the drag force test where stator core is excited by the permanent magnet of the rotor. The core loss reduces in order of NO motor, GO motor, amorphous motor, and nanocrystal motor. The measured core loss is in good agreement with the calculated core loss of finite element method. Since the core loss includes the stator loss as well as rotor loss and permanent magnet loss of sintered NdFeB, the calculation data show that the stator loss of the nanocrystal motor is about one-twentieth smaller than the one of NO motor. Next, to evaluate the motor core loss, motor BF (building factor) diagram is proposed. Finally, fifth order harmonics superimposition to sinusoidal PWM control scheme is researched, and the total loss of the motor drive system is shown to be reduced.