Referring to FIG. 9, in the case of the interior permanent magnet motor 1 having the rotor 20 provided with the flux barriers 25, 26, 27, and 28, the waveform of the voltage induced in the motor 1 is bilaterally symmetrical so that the distortion rate of the counter electromotive force is small. However, in the case of the interior permanent magnet motor 1′ having the rotor 20′ having no flux barrier, the waveform of the voltage induced in the motor 1′ is not bilaterally symmetrical so that the distortion rate of the counter electromotive force is large.

The distortion rate may vary according to the inner flux barrier angle θib and the outer flux barrier angle θob.

FIG. 10 is a distribution diagram illustrating the relationship between the inner flux barrier angle and the outer flux barrier angle of a rotor and the distortion rate of counter electromotive force of an interior permanent magnet motor according to an embodiment of the disclosure. In FIG. 10, the horizontal axis represents ? of the inner flux barrier angle θib, the vertical axis represents ? of the outer flux barrier angle θob, and the inner lines represent the distortion rate.

Therefore, the inner flux barrier angle θib and the outer flux barrier angle θob of the rotor 20 may be determined to be located inside the line indicated by 0.038 in FIG. 10.

Although the interior permanent magnet motor 1 using the C-shaped permanent magnets has been described above, the shape of the permanent magnets 30 used in the interior permanent magnet motor 1 according to an embodiment of the disclosure is not limited thereto.