Eddy-current motor

The eddy-current motor is a type of induction motor, and cup-shaped soft iron is used for the rotor. The picture below is an eddy current motor designed to control the disc of a record player at a constant, low speed. It is a structure in which a cup-shaped rotor, produced from the plastic working of a thick steel plate, rotates. When the number of slots of the stator is increased to overlap the two sets of windings, the magnetic field smoothly rotates, and an eddy current is generated in the rotor by the rotating magnetic field. Due to the interaction between the magnetic field and the eddy current, the rotor rotates smoothly so as to be dragged by the magnetic field.