Precision B– H Analyzer With Low THD Secondary Induced Voltage

This paper deals with an improved precision B-H analyzer based on a power amplifier (PA) with a feedback loop, which is suitable for measuring B-H curves and losses of soft-magnetic toroidal cores. The theory pertinent to the PA-assisted measurement setup is summarized. The presented system is then upgraded with a correction method that gives it the ability to generate accurate and stable secondary induced voltage independent of load, thus assuring more precise measurements of the magnetic field strength H and consecutive specific core losses. The focus is on the proposed repetitive action control method used to achieve a very precise sinusoidal waveform that reduces the peak H while preserving the amplitude of the secondary induced voltage. Two variants of the control method are presented, and their influence on the output waveform are compared. Reasons for choosing one are stated, and measurements done with the proposed method, which shows a considerable improvement, are presented.