| 摘要 |
PURPOSE:To enable to readily match a resonance frequency of a filter device to the frequency of a harmonic current by winding a coil on a core to form a reactor of a filter and providing a bias coil, through which a DC current flows, at the core. CONSTITUTION:A primary coil 71 is wound on a core 71 forming a main part of a reactor 7, a secondary bias coil 73 is similarly wound on the core 72, a variable resistor 74 is connected to one end of the coil 71, and a diode 75 is connected between the resistor 74 and the coil 73. Since the value of dlambda/di is reduced so that a reactance L is decreased when a bias current Ib rectified by the diode 74 is increased, the reactance L can be adjusted to the prescribed value by varying the bias current Ib with the resistor 74. In this manner, a filter device having a resonance frequency to be matched to the frequency of harmonic current thus flowed can be readily formed. |
