| 摘要 |
PROBLEM TO BE SOLVED: To provide an open-phase detection system for detecting open-phase of the input power supply for a power converter comprising a three-phase AC power supply surely at low cost by providing a rectifier circuit and a smoothing capacitoar. SOLUTION: A rectifier circuit 2, a smoothing capacitor 3 and an inverting section 4 constitute a voltage type inverter and variable speed control of an induction motor 5 is performed using three-phase AC input power supply. In such a system, a DC voltage detection circuit 7 is provided and a voltage detection amount is inputted to a fast Fourier transform(FFT) processing section 8 where FFT is performed. 2f and 6f (f: power supply frequency) are then extracted from the processing results and open-phase of input power supply is determined based on the increase/decrease of level (6f component decreases and 2f component increases in case of open-phase). |
