By Panu Kurronen, Product Manager, The Switch
The growing global demand of rare earth metals combined with China’s ever-tightening grip on the material keep pushing up magnet prices. While we at The Switch don’t think the price trend can last too long, we understand that the matter is of great concern for the wind power industry. To tackle with this alarming situation and to meet future needs, the industry needs to change its perspective to open new opportunities.
The Switch has done intense research and development to reduce the amount of magnets needed for the production of p
ermanent magnet generators (PMG). Based on the successful testing 20 different generators, we are in a position to make a third generation, permanent-magnet generator. Combining field experience with state-of-the-art design methods has provided the skills to produce classical machines and innovation to the PMG field.
First, in most PMG designs, the risk of demagnetization of the rotor has been eliminated to the greatest possible degree by using high-dysprosium content rare earth magnets. Dysprosium is the most critical element in the magnet. However, many worst case scenarios related to a PMG design are exaggerated fears, and the demagnetization risk can be safely eliminated even when using lower grade magnets.
Another way to optimize costs is to design effective cooling for the generator. The lower the magnet temperature, the cheaper the selected magnet grade can be. Magnets with a higher temperature class, such as those with dysprosium, are more expensive. Still, more power can also be generated with lower temperature coolant. Even the machine size can be reduced to generate the same output power.We continue to believe that PMG technology in different configurations offers a viable alternative for future turbines. A direct-drive PMG concept with a simple mechanical construction and high efficiency levels well highly suited for offshore turbines. However, the machine’s large physical size often requires large amounts of magnets for the production.
The Switch high-speed PMGs feature a three-stage gearbox. Based on the machine concept and operating range, the magnets once used higher-grade material, and so required higher amounts of dysprosium. The magnets are embedded inside the rotor for increased mechanical strength.
A multi-megawatt medium-speed PMG, such as The FusionDrive requires a fraction of the amount of magnets needed for direct-drive generators with an equal power rating. The FusionDrive power train combines a gearbox, traditionally the largest component in a turbine, and a PMG in a way that produces a smaller and lighter drivetrain than possible by other methods.
Filed Under: Generators, News