ABB says it has developed permanent magnet (PM) generators for applications that call for direct drives, and medium and high-speed. The electrical performance of individual generators can be tweaked for best performance in cooperation with the wind-turbine OEM. For a closer look:

A low-speed gearless design works best in direct-drive applications. The turbine and generator form a compact and structurally integrated unit. The design is said to give free access to all parts for easy installation and maintenance. The simple and reliable low-speed rotor without separate excitation or cooling system results in minimum wear, reduced maintenance requirements, lower life-cycle costs, and a long lifetime.

A medium speed PM generator provides a compact low-speed system. The turbine main bearing and PM generator combined with a single-stage gear box to work at high efficiency and require little maintenance. This design features a simple and reliable low-speed generator rotor without separate excitation or cooling systems. The designs result in less wear, reduced maintenance requirements, lower life cycle costs, and a long lifetime.

And the third design arrangement is a high-speed PM generator similar to a doubly-fed version with even smaller space requirements. It is said to package high power in a small size. Its typical speed range is from 1,000 to 2,000 rpm using a 6 or 8-pole generator. Other pluses are a mechanically identical design to mainstream equipment but without slip rings.

ABB also offers wind turbine generators in conventional synchronous versions.