POWER FACTOR MEASURING METHOD FOR 200V/400V THREE-PHASE CIRCUIT

摘要

PURPOSE:To measure the power factors of a 200V DELTA circuit and a 300V Y circuit in common by using an interline voltage of a specific phase for the 200V DELTA circuit and a voltage between a current detection phase and a neutral point of Y, and correcting an angle when the power factor of the 400V Y circuit is measured. CONSTITUTION:A phase angle measuring circuit 11 measures the phase angle between a voltage input (e) and a current (i) and when a 200V/400V deciding and switching part 12 decides 200V from the result, switching to a power factor arithmetic display part 14 is performed and the phase angle is converted as a 3phiDELTA circuit power factor into a power factor. When the switching part 12 decides 400V, on the other hand, switching to a 90 deg. phase correcting part 13 is performed to correct the phase by 90 deg. and the phase angle is converted as a 3phiY circuit power factor into a power factor by a display part 14. The ground potential of the 400V Y circuit is 400/31/2 and can be set close to the potential of the 200V circuit, so when the ground potential is used as a voltage input, the power factors of a DELTA circuit of 3phi200V and a Y circuit of 3phi400V are measured in common by inputting a voltage and a current from the same input part.