Direct Measurement of DC Hysteresis Losses by Means of Digital and Sampling Techniques

Abstract

The fundamental equation for evaluating the hysteresis losses P h = ??? H dB, transformed for the use of electrical units and approximated as numeric integral Ph = W 1 /W 2 2/1 m A ???? -J ??+J J is sufficiently correct ???? is constant and very small. By continuously changing the magnetizing current in the primary winding w 1 of Epstein frames or ring cores (electronically controlled so that the induced voltage in the secondary winding W 2 does not exceed a fixed limit) the flux ?? can be determined by means of a voltage-to-frequency-converter that generates a pulse train whose frequency is proportional to the input voltage and summing the pulses with an electronic counter. These pulses are scaled to groups of constant number (representing ???? = constant) by means of a preset counter that generates trigger pulses giving commands to a sample and hold digital voltmeter in order to measure the instantaneous values of the current as voltage drop across a standard resistor in the primary circuit. An electronic adder with Nixie display totalizes the current values according to the sign. The measuring procedure takes about 40 s, the accuracy is in the order of some parts in 1000.