| 摘要 |
FIELD: electricity.SUBSTANCE: voltages of the corresponding phase lines (L1, L2, L3) of AC power source (1) of three-phase four-conductor type are rectified by means of full-wave rectifying circuit (11), and it is determined, whether output voltage of full-wave rectifying circuit (11) of pre-determined values is higher or not. If the result continuously points at exceedance of pre-determined value during a certain period of time, connection to AC power source (1) of three-phase four-conductor type is determined as non-erroneous. If the result doe not point continuously at exceedance of pre-determined value during a certain period of time, connection to AC power source (1) of three-phase four-conductor type is determined as erroneous.EFFECT: enhancement of safety.6 cl, 10 dwg |
