| 摘要 |
A control method for variably controlling the speed of an AC motor serving as an inductive load, by use of a frequency converter which is formed of a rectifier, a DC reacter and an inverter connected to a capacitive load, comprises the steps of forcibly commutating switching elements constitating the inverter, when the output frequency of the inverter is below a predetermined value. The switching elements are load-commutated when the inverter output frequency is above the predetermined value and current supplied to the inductive and capacitive loads becomes a phase-advanced reactive current.
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