Controlled Measurement Setup to Characterize a Magnetic Material up into Deep Saturation

This paper presents a controlled measurement setup to characterize a magnetic material up into deep saturation. The material sample in the shape of an ungapped toroidal core is wound with an equally distributed single-layer winding. To characterize this material, the inductive voltage drop and the current of this device under test has to be determined. An aircore coil connected in series to the test coil is used to get a low-noise derivative of the current. Because the inductance of the test coil changes by magnitudes from a demagnetized to a deeply saturated state, the measured voltages suffer from high dynamics. Additionally, the saturation behavior is temperature dependent which prohibits to solve this problem by using an open-loop controller. To saturate the material in a controlled manner, the proposed setup uses feedback control by a microcontroller. This allows to keep the dynamics of the signals within limits, to adjust the distribution of samples on the B-H curve and to select the maximum current without affecting the amplitudes of the voltages. The results show a low-noise measurement of the differential permeability despite the use of simple hardware.