An introduction to typical current waveforms and harmonics for single phase equipment

The problems of harmonics in AC supply systems are well known. Nonlinear loads supplied with sinusoidal voltage draw nonsinusoidal current. The unfortunate effects include resonances of the supply system inductances and capacitances at the harmonic frequencies present in the current waveform, the failure of capacitors due to the extra harmonic currents carried, disturbance of the power system protection, metering and communication equipment, conducted and radiated interference, and voltage waveform distortion which is dependent on the supply system impedance. The need therefore is to limit the levels of such harmonics which are conventionally considered to be injected back into the supply from the converter