An AC alternator with PMG has an AVR which is independently powered from a separate permanent magnet generator (PMG). Made of two parts, the PMG rotor and the PMG stator. The PMG rotor is mounted on the main alternator rotor shaft and voltage is induced in the PMG stator as the PMG rotor moves the permanent magnets.

The PMG (Permanent Magnet Generator) is a system which is used for secondary exciting. The PMG provides stable and reliable electric energy for AVR regardless the generator’s terminal voltage. The generator with PMG excitation system can provide 300% rated current during short-circuit, which occurs for 5–10 seconds.

PMG supplies isolated power to the AVR when the generator shaft rotates. The AVR utilizes the extra power when supplying non-linear loads such as; starting of motors. A clean, isolated, uninterrupted 3-phase waveform is produced when the generator shaft is turning.

A permanent magnet generator (PMG) allows significant benefits instead of a traditional alternator systems. The physical advantages are the reduction of weight and length while the electronic advantages consist in the use of advanced technology designed to maximize the efficiency of the entire energy system.