Low pass filter for DC or mains frequency AC - with resonant frequency damping provided by inherent resistance variation

摘要

The filter is intended for use on power frequency or dc circuits, for example on the input and output of an inverter. The system frequency is thus between 0 and 50 or 60 Hz, and the filter resonant frequency around 300-360 Hz. The filter comprises a series inductor and a parallel capacitor. The damping of resonant and higher frequencies is improved by constructing the inductor (12) such that, at these higher frequencies, the current concentration in the conductors increase rapidly and thus raises the effective ohmic resistance of the coil. The change in resistance is determined by the dimensions, in partic. the radial dimension, of the conductor used in the winding, and the shape of the magnetic field of the inductor.