Hysteresis loss

Loss as heat in magnetic materials in a motor caused by the hysteresis phenomena. Hysteresis loss is almost proportional to rotational speed, the area of the hysteresis loop shown in fig. (a), the volume of the magnetic body where hysteresis occurs and the frequency of the magnetic field change. For this reason, the hysteresis loss in the iron core of the motor is basically proportional to the rotational speed. However note that the hysteresis loss is part of the iron loss and the other component is the eddy-current loss which is proportional to the square of speed. In the case of hybrid stepping motors shown in fig. (b), little iron loss occurs in the permanent magnet at the center of the rotor, but since the frequency of change to the magnetic field of the fine toothed portion of the stator and the rotor is high, major iron loss occurs here.