| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent error determination of ground direction detection by: inverting a phase of zero phase current detected in a prescribed period just before a prescribed period; and adding it to zero phase current detected at every prescribed period. Ž<P>SOLUTION: A ground detecting apparatus includes: a zero phase current waveform recording circuit 1 recording detected zero phase current Io for a first prescribed period; a zero phase current waveform storing circuit 2 storing a recorded waveform value; a zero phase current correcting circuit 3 inverting stored zero phase current, adding it with detected zero phase current and outputting corrected zero phase current Io'; a corrected zero phase current amplitude value recording circuit 4 recording corrected zero phase current at starting time of a second prescribed period; a corrected zero phase current amplitude value storing circuit 5 storing a recorded amplitude value; a first ground determining circuit 6 operating a corrected zero phase current amplitude value difference, operating an inclination value based on the difference, outputting a prescribed value when the value is equal to or more than a setting value, increasing a count value when the value continues and outputting a ground determining signal when the value equal to or more than the setting value; a second ground determining circuit 7 outputting a ground determining signal when corrected zero phase current equal to or more than the setting value and equal to or more than setting time; and a ground direction detecting circuit 8 operating a phase difference between zero phase voltage Vo at that time and corrected zero phase current when both ground determining signals are inputted. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
|
