Prediction of Power Supply Generated Interference

A technique for predicting conducted interference on input power lines of ac to dc power supplies with diode rectification and smoothing capacitors is presented. Derivation and curves are presented which define the amplitude and conduction angle of the diode current for single- and three-phase supplies. The envelope of the Fourier spectrum of this waveform is then estimated. An example is given which illustrates the use of the curves and the accuracy of the prediction.