| 摘要 |
PROBLEM TO BE SOLVED: To provide an active filter device that removes commercial frequency components superimposed on a common-mode current. SOLUTION: The active filter device reduces noises by the common-mode current flowing on the power-supply line between a three-phase AC power supply 1, by using a power-supply line 1b as the grounding phase and a power converter 3 for converting an AC power supplied from the power supply into a specified AC power or DC power and supplying a load 5 with the AC power or DC power and having a grounding terminal E in a box body, while having Y capacitors 5A to 5C on the input side. The active filter device has a current-detecting means 10 for inserting the power-supply lines 1a to 1c and a detection line 10a, detecting the common-mode current by the detection line 10a and outputting a common-mode current-detection signal and an amplifying means 11 which is connected between the power-supply line 1b, having the grounding phase and a ground, amplifying the common-mode current-detection signal at an amplification degree 1 and making the common-mode current-detection signal flow between the power-supply line, having the grounding phase and the ground via a capacitor 12. The device further has removing means 20A, 20B, 21A and 21B for flowing a current between the power lines 1a, 1c having the non-grounding phase and the power line 1b having the grounding phase; adding the current to the common-mode current-detection signal; and removing the commercial frequency component in the detection signal. COPYRIGHT: (C)2009,JPO&INPIT
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