When AC current passes through a wire, an alternating magnetic field will be generated around the wire. The internal part of the whole conductor in the alternating magnetic field will produce induced current. Because this kind of induced current forms a closed loop inside the whole conductor, much like the vortex of water, it is called eddy current. Eddy current will not only waste electric energy, reduce the efficiency of electrical equipment, but also cause heating of electrical appliances (such as transformer core), which will affect the normal operation of equipment in serious cases.