| 摘要 |
PROBLEM TO BE SOLVED: To provide a phase failure sensing method which senses a phase failure of an output for a three phase voltage source type inverter and its circuit. SOLUTION: CTs 3-5 are provided on respective lines from an inverter main circuit 2 to a motor 6. A phase failure sensing circuit which is constituted of comparison arithmetic circuits 21-23, polarity arithmetic circuits 31-33, AND circuits 34-36 and a judgement arithmetic circuit 50 is disposed. A pulse width signal which is produced by the respective AND circuits 34-36 near a zero current point passing point by the respective sensed values of the CTs 3-5 is measured, and a phase failure sensing signal is outputted from the judgement arithmetic circuit 50 by sensing the measured value which exceeds a predetermined value. |
