| 摘要 |
PURPOSE:To diminish the change in the sine waveform and prevent a thrust from being changed and harmonic from being generated, by switching the waveform at a point where the momentary values of two sine waves coincide with each other. CONSTITUTION:When a sine wave pattern 1 is switched to a sine wave pattern 2, then a phase difference between the two sine wave patterns is detected by a phase comparator 6. By the patterns set within a regulated range and coming to a change-over speed or more, the output of waveform switching permission 6a is generated. Then, the momentary values of two sine waves are compared with each other by a comparing section 4, and at a point where the values coincide with each other first, the output of switching command 5a is directed to a waveform switching section 7, and a synchronous sine wave is switched. As a result, the sudden change of the waveform is less, and so a propelling force and a power source side are less influenced by the sudden change. |
