ELECTRIC LEAK DETECTING CIRCUIT AND ELECTRIC LEAK DETECTING METHOD

摘要

Provided is an electric leak detecting circuit available at a reasonable cost. Before starting an operation of a multi-phase AC motor (3), power switch unit (2)(switches (21 to 23)) is turned OFF and a switch (4) is turned ON. For example, if an electric leak occurs in the multi-phase AC motor (3), current flows into a line formed by a multi-phase AC power source (1), an output line (81), a second line (85), and a current detecting resistor (5). A judging unit (72) detects an electric leak according to a current value flowing in the current detecting resistor (5) and detected by a current detection unit (6). If the current value exceeds a predetermined value, the judging unit (72) judges that an electric leak has occurred. That is, it is possible to detect an electric leak from the current flowing in the output line (81). As compared to a case of detecting an electric leak according to the total of currents flowing in output lines (81 to 83), it is possible to use a cheap current detection unit.