Synchronous motor

In induction (asynchronous) motors the rotor rotates slower than the magnetic field that moves around him. In synchronous motors the rotor is rotated simultaneously with the field. In simple synchronous motors the rotor consists of one or more permanent magnets, their poles are attracted to different poles of the rotating magnetic field, so they rotate at the same speed. Sometimes, instead of permanent magnets in the rotor are electromagnets, but the principle remains the same. In another type synchronous motors are used jumping alternating current to create a magnetic field, which step by step rotates the rotor gear.
Most of the motors create rotational movement. But in some of them the windings of the stator are opened and placed on the same line, which creates a magnetic field which moves linearly together with conductive material. Such engines are called linear induction. They are used to open sliding doors, transporting Luggage at airports, in high-speed trains.