| 摘要 |
Voltages of respective phase lines (L1, L2, L3) of an alternating-current power supply (1) of three-phase four-line type are rectified by a full-wave rectification circuit (11), and whether an output voltage (11) of the full-wave rectification circuit is above a predetermined value or not is determined. If a determination result thereof continuously indicates being above the predetermined value for a constant time, connection to the alternating-current power supply (1) of three-phase four-line type is determined to be not an error. If the determination results does not continuously indicates being above the predetermined value for the constant time, the connection to the alternating-current power supply (1) of three-phase four-line type is determined to be an error. |
