Harmonic Distortion Canceller for Line-Operated Apparatus.

This paper presents new higher-harmonic distortion canceller for line-operated apparatus with a relatively small power rating. Almost all types of electronic equipment employ a capacitor-input smoothing circuit, and their input currents contain many higher-harmonic components. In industrial use, the popular phase-controlled rectifiers also generate higher harmonics. These higher-harmonic currents distort the line voltage waveforms by impedance of commercial ac lines, and affect all the equipment connected to those lines. This distortion causes a vibration or heat in the smoothing capacitor. In the worst case, fire may break out; several instances of this have been reported recently However, it seems that existing countermeasures are not adequate for users of equipment affected by the higher harmonics. The proposed circuit was constructed by using our original noise superimposer, and decreased the total harmonic distortion (THD) from 4.92% to 0.69%.