Permanent magnet generators (PMG), also called permanent magnet alternators (PMA), use the magnetic field of a rotor to provide a stable, reliable power source.
Permanent magnet generators and permanent magnet alternators do not require a DC supply for excitation circuit, nor does it need to have slip rings or contact brushes. Permanent magnets are embedded in the steel rotors creating a constant magnetic field. The stator carried windings are connected to an AC supply to produce a rotating magnetic field.
At a synchronous speed, the rotor poles lock to the rotating magnetic field. The rotor and the magnetic field rotate with the same speed because the magnetic field is generated through a shaft-mounted permanent magnet mechanism while the current is induced into the fixed frame.