Wednesday, May 2, 2012

No. 502: Two rare earth-less vehicle motors are put into practical use before too long (May 3, 2012)

Two universities successfully conducted experiments of a rare earth-less vehicle motor. Tohoku University drove an electric vehicle loaded with a rare earth-less motor that it had developed in alliance with JEF Holdings and ENAX that is a lithium-ion battery manufacturer. The research team will also drive a small-size electric bus loaded with a rare earth-less motor coming July. Tokyo Institute of Technology verified a rare earth-less motor using a commercially-available e-vehicle and confirmed that there was virtually no difference in noise and ride quality between an rare earth-containing motor and the new rare earth-less motor. 

The two rare earth-less motors are switched reluctance motors. The concept of a switched reluctance motor was invested in the 1830, and part of it was put into practical use in the 1950s. However, it was too big and too noisy to be built in an e-vehicle. It was widely believed that the switched reluctance motor would be applied only to construction and agricultural machinery. The research team of Tohoku University devised a system to strictly control the current transmitted to a motor using semiconductors and reduced the rotational fluctuations. The team members drove a single-seater e-vehicle with the developed motor that weighs 220 kg at 40 km/h and confirmed that both acceleration and deceleration were very smooth. They are confident that it will not be difficult to increase the speed to 60 km/h if the system with improved system. They are developing a motor for an electric bus that will be driven for experiment coming July.

A professor from Tokyo Institute of Technology and a professor from Tokyo University of Science drove an e-vehicle loaded with the newly developed motor and confirmed that it has almost the same energy efficiency as the motor built in a Toyota’s hybrid vehicle. However, the former is 15% heavier than the latter. The two professors are trying to reduce the weight in alliance with automakers.  

  Switched reluctance motor test

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