| 摘要 |
<p>When an AC ground fault occurred on the secondary side of a three-phase inverter circuit 3 of a step-up power supply circuit 1, and when a flying capacitor C1 reaches a continuous charging state while forming a charge circuit including a ground fault resistance RL due to an AC ground fault, the ground fault resistance RL due to an AC ground fault is obtained using the same method as that for a positive-side ground fault resistance RLp or a negative-side ground fault resistance RLn, due to a DC ground fault. Accordingly, when the flying capacitor C1 reaches a continuous charging state while forming a charge circuit including the ground fault resistance RL due to an AC ground fault, and even when a switching duty ratio of respective semiconductor switches of the three-phase inverter circuit 3 varies, a value of a ground fault resistance RL due to an AC ground fault can be accurately obtained without using the data of the switching duty ratio of respective semiconductor switches of the three-phase inverter circuit 3.</p> |
