| 摘要 |
PURPOSE:To start an inverter stably by using a power transistor having normal proper capacity by making the frequency of a carrier on starting higher than that of a carrier on operation. CONSTITUTION:The frequency of a carrier 12 used on starting is made higher than that of a carrier 22 employed on operation. A PWM waveform 10 on starting has narrow pulse width, and a PWM waveform 20 on operation has wide pulse width. Accordingly, currents increase for a period when the impedance of an induction motor is small on starting, but the breakdown of a power transistor can be avoided because of narrow pulse width.
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