| 摘要 |
PURPOSE:To suppress local overheat generated on the conductor piece of a rotor, by changing the frequency of a carrier wave repeatedly, and by controlling harmonic component included in inverter output voltage. CONSTITUTION:From carrier oscillators 8a, 8b, 8c, the carrier waves of different frequency are generated. By a switching device 7, according to signal fed from a time setting unit 6 via a signal line 13, one of three sorts of carrier waves is selected, and the carrier wave is fed to a comparator 5 through a signal line 14. By changing the carrier waves of low frequency and the carrier waves of high frequency repeatedly in order in this manner, heat generation is suppressed, and the span of life for a motor is lengthened, and magnetic noise is attenuated. |
