There is no single winning design of a traction motor - one of the main elements of cost in a vehicle. For example, reluctance-assisted synchronous motors are proving useful and some motors switch from synchronous to asynchronous at high speed. Nonetheless, even in the over-simplified form of synchronous vs asynchronous there is no firm choice for any category of vehicle. Asynchronous wins for large electric vehicles such as e-bus but only by the smallest of margins. Synchronous permanent magnet motors win for smaller vehicles but the situation is fluid.
uses asynchronous motors. John Deere
uses switched reluctance synchronous motors without magnets. Supplier Nidec
rightly sees these as having the lowest inherent cost - no magnets with their expensive rare earths and little copper. By designing its own traction motors, Zero Motorcycles
in the USA has made the remarkable breakthrough of increased efficiency and heat distribution to the extent of abandoning the expense, weight and volume of water cooling. This motor is behind the superlative acceleration of its on and off-road e-motorbikes, a major selling feature.
Electric motors are merging into powertrains or merging with controls and gearing. Recently Scientists from Nanyang Technological University (NTU)
and German Aerospace Centre (DLR) invented a 2-in-1 electric motor which increases the range of electric vehicles
. This novel, space-saving design allows the use of bigger batteries
, which can increase the range of electric vehicles by a precious additional 15 to 20% they claim, the sort of contribution obtained from multiple energy harvesting
and other imminent advances. Little wonder that IDTechEx sees a tipping point in sales of pure electric cars by the end of the decade.
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Top image: Wikipedia