| 摘要 |
PROBLEM TO BE SOLVED: To protect the driver of an induction motor which is applied to the driving of the fan of an air-conditioner, from an overcurrent caused by an external strong wind, an overvoltage caused by regeneration, etc. SOLUTION: A voltage limiting means 7 which limits the upper limit of the output voltage of an inverter circuit 2, a voltage slow-up means 8 which converts the output signal of an output voltage instructing means 4 into a gently rising signal when the signal rises, a voltage slow-down means 9 which converts the output signal of the output voltage instruction means 4 into a gently falling signal when the siginal falls and a feed cutoff treatment means 11 which makes the output signal value of the output voltage instruction means 4 zero at the time of feed cutoff and outputs a first feed cutoff signal after a lapse of certain time from the cutoff are provided. |
