Referring to FIG. 6, there is no flux barrier at both ends of the permanent magnet 30 of the rotor 20′ unlike FIGS. 2 and 3. Graphs in which the waveform of the voltage induced in the motor, the torque ripple, and the distortion rate of the counter electromotive force of the interior permanent magnet motor 1 having flux barriers 25, 26, 27, and 28 at both ends of the permanent magnets 30 as illustrated in FIGS. 2 and 3 are compared with those of the interior permanent magnet motor 1′ having no flux barrier at both ends of the permanent magnets 30 as illustrated in FIG. 6 are illustrated in FIGS. 7, 8, and 9.

FIG. 7 is a graph illustrating the waveform of voltage induced in an interior permanent magnet motor according to an embodiment of the disclosure when a rotor of the motor has flux barriers and when the rotor of the motor has no flux barrier. In FIG. 7, the horizontal axis represents the rotor angle (degrees), and the vertical axis represents the voltage (V).

Referring to FIG. 7, 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 sinusoidal and bilaterally symmetrical. However, in the case of the interior permanent magnet motor 1′ having the rotor 20′ without the flux barrier, the waveform of the voltage induced in the motor 1′ is not bilaterally symmetrical.