| 摘要 |
PROBLEM TO BE SOLVED: To efficiently suppress a higher harmonic current. SOLUTION: A higher harmonic suppressing circuit 10 is constituted of an active filter 11, a load current detector 12 which detects a load current, a tertiary higher harmonic current extractor 13 which extracts a tertiary higher harmonic current from the detector 12, a level discriminator 15 to which the tertiary higher harmonic current and load current are inputted, a gate block circuit 16, etc. The circuit 10 compares the tertiary higher harmonic current with a present prescribed value by means of the level discriminator 15 and, when the current exceeds the prescribed value, stores the value of the load current by operating the active filter 11 by outputting a filter operating signal to the gate block circuit 16. While the filter operating signal is outputted, the circuit 10 compares the load current with a stored current value and, when the load current becomes smaller than the stored current value, stops the active filter 11 by stopping the output of the filter operating signal. |
