Device for the automatic determination of the magnetic properties of electrical steel sheet

In order to investigate the magnetic properties of soft magnetic materials, especially of electrical steel sheet, with high accuracy and minimal manual operation, we have developed a computerized control and measuring device which cooperates with all commonly used magnetization equipment such as an Epstein frame, single sheet yoke etc. The device delivers a sinusoidal voltage with programmable frequency and amplitude which is used to control a power amplifier supplying the magnetizing current. The following magnetic quantities are derived from the induced voltage in a secondary winding and from the voltage drop at a series shunt in the primary circuit or, alternatively, from a tangential field sensing coil: peak value of magnetic flux density, rms value of induced voltage, remanent induction, peak value of magnetic field strength, rms value of magnetic field strength, coercive field strength, and total maqnetic loss. All quantities are converted to dc voltages for analog readout and, after digitization, for computer storage. The time dependence of H(t) or dH(t)/dt and B(t) or dB(t)/dt can be sampled at up to 256 points per period, allowing the reconstruction of the hysteresis loop; thus all quantities can be obtained by analog and digital signal processing as well. The frequency range of the apparatus is 8 Hz to 1023 Hz.