| 摘要 |
PURPOSE:To prevent a beat phenomenon from becoming conspicuous by changing chopper frequencies from each other according to an inverter freqnency varying with the lapse of time by means of an unstable domain decision circuit. CONSTITUTION:Two fixed chopper frequencies and a frequency domain, where a beat phenomenon becomes conspicuous, are set beforehand at an unstable domain decision circuit 16. Also, one fixed chopper frequency is selected as a chopper frequency outputted from a normal changeover circuit 17. If an inverter frequency outputted from a pulse distributor 15 varies with the lapse of time and six times as much as said frequency crosses an unstable domain, the unstable domain decision circuit 16 outputs a changeover signal, which changes the chopper frequency over to the other fixed chopper frequency.
|
