A Technique of Measuring Amplitude and Harmonic Content of Surge Voltages in Machine Windings During Switching

A combination amplitude and frequency discrimination technique has been developed to investigate the amplitude and harmonic content of surge voltages in electric machinery during switching. Bypass networks of 10 kc (kilocycles per second), 100 kc, and 2 mc (megacycles per second) were used in conjunction with a voltage divider to measure surges voltages at the line terminals of an induction motor during plug reversing. These bypass networks enabled measurement of the voltage amplitude of a surge as a function of its harmonic content. Oscilloscope photographs were used to establish the amplitudes of the surge voltages having frequency components between 0 and 30 mc.