| 摘要 |
Before an inverter (INV) is put into operation, only a switch (K0) of R phase is made conductive while an switch (K11) of S phase and a switch (K12) of T phase are kept open in a group of switches (SW). At least one of three low arm side switches (Q21, Q22, Q23) is made conductive. When a ground fault (J0) that is due to insulation failure of a motor (P) is generated, a current flows from a power supply of R phase through the conductive one or ones of the low arm side switches, a low arm side diode (D 14) of R phase and the switch of R phase. This current (IM) is detected by a current transformer (CT) that has conventionally been provided to detect whether or not an overcurrent flows during the operation of the inverter. When the above-discussed ground fault is not generated, this current does not flow as a matter of course. That is, it is possible to detect whether or not a ground fault is generated in the motor based on the presence or absence of this current. |
