The growing global demand of rare earth metals combined with China’s ever-tightening grip on the material keep pushing up the magnet prices. While we at The Switch don’t think that the price trend can last for 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 up to new opportunities.
The Switch has done intense research and development to reduce the amount of magnets needed for the production of permanent magnet generators (PMG). Based on the successful testing of 20 different machine types, we are in a unique position to make third generation permanent magnet machines. By combining our extensive field experience with our state-of-the-art design methods, not only do we have the skills to produce classical machines but we can also bring new innovation to the PMG field.
Firstly, in the majority of current 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, as dysprosium is the most critical element in the magnet. However, many of the worst case scenarios related to a PMG design are exaggerated fears, and the demagnetization risk can be safely eliminated even by using lower grade magnets.
Another way to optimize costs is to design an effective cooling system for the machine. The lower the magnet temperature, the cheaper the selected magnet grade can be, as magnets with a higher temperature class, such as dysprosium, are more expensive. Still, more power can also be generated with lower temperature coolant or even the machine size can be reduced to generate the same output power.
We at The Swicth 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 is 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 used have to be of a higher grade and consequently requires 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 equal power-rating. The FusionDrive™ power train solution integrates a gear, traditionally the largest component in a turbine, and a PMG in an innovative way – together smaller in size and lighter in weight than any other solution in the market.
Panu Kurronen, Product Manager, PMG
