| 摘要 |
PURPOSE:To prevent that a harmonic current of a certain order is expanded to an extent higher than the amount of generated heat of a harmonic generating source on the load side and also prevent heating of a capacitor on the load side by cutting off the harmonic by detecting expansion of harmonic current in a load and then detecting such expansion for each harmonic. CONSTITUTION:A harmonic current 1L is enlarged when a load which becomes a low impedance for harmonic of a capacitor is applied in the load side. For example, it is assumed that enlargement is generated by the 13th harmonic. In this case, the 13th DC signal Pd exceeds the present value Pr and an output signal Ph of comparator becomes high. Moreover, its output signal Ph appears at the output of a second gate circuit 16d, then turned to a low level via a first inverter 21d to become the first gate signal Gd. Thereby, when it is detected that the 13th harmonic among the harmonics current IL is enlarged in the system condition, the first gate circuit 13d is turned off. Accordingly, harmonics assisting enlargement can be cut off. |
