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The analysis of minor hysteresis loop behavior during partial alternating flux reversal in toroidal cores with a rectangular hysteresis loop is considered. A simple flux-reversal model is proposed on the basis of which, with the aid of dimensionless units, the asymmetry of minor hysteresis loops is derived. The drift of minor hysteresis loops during alternating flux reversal is investigated on the basis of loop asymmetry and by means of a proposed indirect method. The method involves compensation of the minor-loop drift by means of a dc component of the exciting field, the magnitude and sense of which are a measure of the drift. The experimental section deals partly with a qualitative comparison of the character of the actual asymmetry of a minor loop with that derived from the flux reversal model, and partly with comparing the actual minor-loop drift to the drift derived theoretically on the basis of the indirect method. Experimental results indicate that in the case of the 50 percent nickel-iron alloy, cold-rolled at a great reduction, there appear additional factors which affect the instability of the minor loop. This effect is further investigated, and a simplified mechanism is proposed for its stimulation. Finally, the proposed mechanism is verified experimentally.