FREQUENCY-DEPENDENCE OF LOSS-IMPROVEMENT OF GRAIN-ORIENTED SILICON STEELS BY LASER SCRIBING

Dynamical hysteresis loops of unscribed and laser scribed grain oriented silicon steels were measured in the frequency range from 0.05 to 500 Hz for polarizations from 1.4 to 1.7 T to determine frequency dependent loss improvement. For low frequencies the plot of fractional loss change show increased power losses due to laser scribing. However by increasing the frequency the fractional loss change is decreased until an optimum in relative loss reduction is reached, dependent on laser treatment. The loss change due to laser scribing depending on frequency can be explained by the assumption that the number of movable domains is increased by the same amount for all frequencies.