Precise characterization of soft-magnetic materials at high saturation

The presented paper deals with a computerized measuring system for evaluating magnetic properties of soft-magnetic ring cores (in compliance with the IEC60404-2 standard). A measuring set-up with a feedback power amplifier is introduced. Its basic operation is explained and an upgraded version is presented. Its main feature is a superior control loop based on a repetitive action control method which assures an accurate and stable secondary induced sinusoidal voltage waveform without voltage zero-crossing distortion caused by a large magnetizing current. Two variants of the repetitive method are presented which provide more realistic measurements of magnetic field strength H at the specified amplitude of the secondary induced voltage. Measurements done without and with the repetitive action corrector are presented and discussed. Reasons for choosing one variant are given and results that confirm the improvement over a conventional approach without the repetitive controller are shown.