Measurement and analysis of magnetostriction of nanocrystalline alloy laminations under medium-frequency excitation

Nanocrystalline alloys, widely used as core materials of medium-frequency transformers, require accurate measurement of their magnetostriction to calculate the core vibration and noise during the transformer design phase. A synchronous measuring system consisting of a magnetizer with an optical reflector and a laser vibrometer is constructed to measure the 1D magnetic loss and magnetostriction properties under medium-frequency excitation. The annealed nanocrystalline alloy sheets are laminated and measured in this study due to their softness and brittleness. The influence of single- and double-yoke magnetic circuit structures on the measurement of magnetic properties is discussed. The hysteresis loops and magnetostriction of nanocrystalline alloy laminations with a double-yoke structure are measured from 1 kHz to 10 kHz. The results indicate that the hysteresis loops widen as the frequency increases, resulting in increased losses. Moreover, the peak-to-peak value of magnetostriction first increases and then decreases with increasing excitation frequency, and the magnetostriction curves exhibit a transition from elongation to contraction. These results can provide data support for the design of cores for medium-frequency electromagnetic devices.