The hysteresis power loss is caused by forcing the magnetic material around the hysteresis loop. Each time the magnetic domains change direction, external energy is required. As shown in Sec. 1.2.4, the area inside the hysteresis loop represents energy (Fig. 1.22). Each time the magnetic material is forced around
the hysteresis loop, energy equal to the area inside the hysteresis loop is lost. Therefore, the hysteresis power loss is proportional to the product of the hysteresis loop area and the cyclic frequency, as shown here. The outer hysteresis loop area wH, J/m3, can be approximated as a rectangle having a height of 2BS and a width of 2HC.
Dividing the hysteresis loop area by the magnetic material density p and multiplying it by the cyclic frequency f gives the outer loop hysteresis core loss PH, W/kg, as follows.
The area of a minor hysteresis loop can be approximated by substituting the peak flux density BP in place of the saturation flux density BS, and by assuming that the minor loop width remains constant.
It should be noted here that the hysteresis core loss is directly proportional to the excitation frequency.