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Net Journal 9

New motor concept borne from rare earth substitute materials

――How do ferrite magnet motors for HEVs work?

竹本 真紹准教授

Takemoto: At first, we thought that we could obtain sufficient output with ferrite magnets simply by extending conventional neodymium magnet motors. But after carrying out analysis, we understood that the properties of neodymium magnets and ferrite magnets differ significantly. We couldn’t just replace neodymium magnets with ferrite magnets. We had to rethink the design of the motor itself.

We were able to develop the concept of a motor design specialized for ferrite magnets (Explanation 3/Figure 1) relatively quickly. But what was really difficult was finalizing the design. Because automobile motors require a high level of performance, all components must fit together meticulously, down to the smallest parts. And, in addition to performance, we had to optimize detailed parts so we could arrive at a design that withstands production and industrial productization requirements, all the while conducting repeated simulations and analysis.

Our efforts culminated in the development of a “newly-structured 50 kW ferrite magnet motor for hybrid electric vehicles,” which was jointly announced with NEDO in September 2010. We developed a motor that could generate 50 kW of power, rivaling rare earth-using neodymium magnet motors for HEVs. This achievement has great promise for strengthening Japan’s competitiveness in the development of next-generation automobiles, which has intensified in recent years.

――What kind of changes will the commercialization of ferrite magnet motors bring?

Takemoto: I think a major achievement is the ability to use ferrite magnets in devices that are easy to industrialize. But in actuality, we will still need to use rare earth elements in the future. Rare earth neodymium magnet motors are extremely high-performance, and their designs and production techniques are advanced. Because of this, there are also students in our lab who are researching ways improve the design and performance of neodymium magnet motors. What we are aiming for is not a simple “let’s rid ourselves of rare earth,” but developing alternative methods so we can continue to use rare earth materials effectively from here on. I think it is important to broaden the range of choices. For example, we can use rare earth for high-performance luxury cars, while using alternative materials for inexpensive compact cars.

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(Photo 1) Rare earth-free newly-structured 50 kW ferrite magnet motor for hybrid electric vehicles

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