| 摘要 |
<P>PROBLEM TO BE SOLVED: To detect an open-phase state, wherein operations of some of conductor switches that operate an inverter circuit are interrupted, exactly and in a short time without false operations regardless of the situation of the inverter circuit. <P>SOLUTION: An output voltage waveform of each phase of the inverter circuit 3 is detected by an AC voltage detection means 7; the AC voltage waveform of each phase is traced by a each-phase AC voltage waveform trace means 9; voltage peak values of the positive side and the negative side of the AC voltage waveform are continuously recorded by a peak-voltage record means 10; the difference of the voltage peak values of the plus and minus sides is compared with a prescribed value by a comparison means 12; and the inverter circuit 3 is protectively operated by a gate control means 14 when a state that the difference of the voltage peak values exceeds the prescribed value is continued for prescribed hours. <P>COPYRIGHT: (C)2003,JPO |
