Motors and Drives
Such has been the concern that some manufacturers of servo motors have had to charge customers ‘servo surcharges’ because of the high prices paid for the rare-earth magnets; while some manufacturers charge a flat rate per motor, others levy a charge that relates more closely to the weight of rare- earth magnetic material contained in each motor.
Researching alternatives
Manufacturers of motors and products that incorporate motors, as well as government agencies, have started to take the view that the situation is unsustainable and that alternative technologies need to be developed. In the UK, a group of specialist engineering technology companies has won funding to undertake research into the development of the next generation of electric vehicle drivetrain systems that will reduce significantly the future dependency on rare- earth metals, as most motors for electric and hybrid vehicles currently contain significant amounts of rare-earth metals such as neodymium and dysprosium. Sevcon is leading the collaborative project, with other participants being Cummins Generator Technologies and Newcastle University’s Power Electronics and Drives Research Group; the aim is to develop a new type of ‘no rare-earth metals’ electric traction drive system for use in hybrid and pure electric vehicles. Instead of using conventional motors with rare-earth magnets, the team is to develop a drive system based around advanced high torque density switched reluctance (SR) motors. Over £500 000 in matched funding has been received from the government-backed Technology Strategy Board (TSB) and the Department for Business Innovation and Skills (BIS). It
is anticipated that the project should result in a drive system being ready for volume production within four years. The drive system design under development will not only
use SR motors to avoid the need for rare-earth magnets, but will also replace traditional electronic control systems with new types based on power electronics. As well as providing sufficient power, the new-generation drive system will be designed to be both cost-competitive and suitable for high-volume manufacture.
Fig. 2. Mike Dowsett, vice president of business development at Oxford Yasa Motors, with a yokeless and segmented armature motor rated at 60kW and 200Nm.
Fig. 3. A pair of Yasa 750 motors, each with 750 Nm peak torque, are installed in the Westfield iRacer. 54
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