Measurement of rotating flux in silicon iron laminations

A method of calculating the magnitude and direction of the instantaneous flux density in a thin lamination of magnetic material is described. The technique was demonstrated by measuring the rotating flux in samples of mild steel, grain-oriented silicon iron, and at a point in the T-joint of a three-phase, three-limbed transformer core. The flux in the mild steel sample was found to rotate at a constant angular velocity and to be constant in magnitude. In the silicon iron sample, and at a point in the T-joint, the flux density varied both in angular velocity and magnitude. A large 150 Hz component of rotational flux was found to cause high localized power loss in the T-joint. The power loss was measured using the "initial rate of rise of temperature method" and was compared with the predicted rotational hysteresis loss.