Magnetic Material Test by Waveform Sampling

The evaluation of magnetic steel for electric motor applications has been most effectively done with ring samples rather than Epstein samples. However, the tests required skilled technicians and considerable time to wind magnetizing and excitation coils and to compute required magnetic variables. A test system is presented that is fast and requires no special skills. Yet the controls and calculations required by standard magnetic testing are performed. A simple three-turn fixture replaces toroidal windings, and the necessary flux waveform control is achieved by a power amplifier and feedback control. Calculations and the test report are supplied by a microcomputer that also replaces meters by data sampling. The tester can also be used to evaluate the yokes of stator cores, and losses can be separated into hysteresis and eddy current by the two-frequency method.