PMSG

A permanent magnet synchronous generator (PMSG) is a type of electric machine that converts mechanical energy into electrical energy. It uses permanent magnets on the rotor to provide the magnetic field, while the stator carries three-phase windings. The electrical output is synchronous with the rotor field and typically requires a power converter to interface with the grid, especially in variable-speed applications.

Construction and operation: In a PMSG, the rotor contains permanent magnets arranged to produce a constant magnetic field. The stator has three-phase windings connected to a converter. In wind turbine implementations, PMSGs are often used in direct-drive configurations that omit a gearbox or with a gearbox for higher-speed turbines. Because the field is supplied by permanent magnets, no rotor excitation is needed, reducing copper losses and simplifying maintenance. Some PMSGs use interior permanent magnets or surface-mounted magnets, and cooling may be air-, water-, or oil-cooled.

Advantages and challenges: PMSGs offer high efficiency, good torque density, and ease of control for variable-speed operation. They avoid slip rings and, in direct-drive designs, reduce mechanical complexity. Drawbacks include the cost and supply risk of rare-earth magnets, potential demagnetization at high temperatures, and the need for power electronics to interface with the grid.

Applications: The technology is widely used in modern wind turbines, particularly direct-drive machines for offshore installations. It is also used in small-scale hydro, microgrids, and other renewable-energy or distributed-generation contexts where compact, efficient generators are advantageous.