By Dr Peter Harrop, chairman, IDTechEx
All electric vehicles have at least one traction motor, so the market for electric vehicle traction motors is one of the largest markets for electric vehicle parts and a primary determinant of the performance and affordability of a given vehicle. IDTechEx Research finds that in 2013 44.6 million electric motors will be needed for vehicles, rising to 147.7 million in 2023.
Whether those vehicles are hybrid or pure electric is not a primary determinant of motor type. More important are such factors as whether they are to fly or be used on land or in water. For example, electric aircraft need the very lowest weight for high power to weight ratio, whereas size for a given performance is of interest in underwater vehicles because the larger they are, the more difficult it is to push water out of the way in order to move forward. Then there is the cost aspect; being very important with e-cars and e-bikes for example, and much less so with military and certain professional vehicles.
The duty cycles of traction motors vary hugely. All this adds up to a huge variety of electric traction motor designs with more than one good solution for a given application much of the time. On the other hand, the required cost-performance trade-off can be met by choosing between in-wheel, corner unit and in-board motors of various types so the choice is very large.
There is considerable fragmentation of the industry, with about 150 manufacturers of many different traction motors types today. Much of this is justified by the very varied demands of different vehicles. Nonetheless, patterns emerge. In 2023, possibly 15% of the industrial and commercial electric vehicles sold in that year will have more than one traction motor. More impressively, it is possible that 30% of cars and 40% of military electric vehicles sold in that year will be multi-motor. In other sectors of electric vehicles land, water and air the adoption of more than one motor will be more modest, so the number of motors sold for new vehicles will not be hugely larger than that for the number of vehicles sold in 2023.
Tokyo University of Science, Tokai University, Hokkaido University, Mitsubishi Electric and others are working on a continuum of opportunity from synchronous traction motors that have magnets that do not contain dysprosium or neodymium, ones that have smaller magnets, sometimes using more of the reluctance phenomenon and ones that are entirely switched reluctance. There is similar work elsewhere in the world at companies such as SR Drives in the UK, a subsidiary of Nidec Japan, trialling big switched reluctance motors on buses etc. and selling its first output for large vehicles in 2012. Renault is also looking at the switched reluctance option. However, for the coming decade, most of the market will be served by asynchronous traction motors, mainly for large vehicles, and permanent magnet synchronous motors in much of the rest and certainly aircraft. Whether the synchronous motor has a sinusoidal or trapezoidal waveform is less of concern.
However, all this is an over-simplification because there is a continuum of options intermediate between all of these. The result is that, although the traction motor industry is massively fragmented, it offers many on-going opportunities for small- and medium-sized businesses. In the short term, success is correlated more with who backed the successful vehicle manufacturers. For example, pure electric cars continue to be massively outsold by hybrid electric cars. IDTechEx forecast that continuing throughout the coming decade but with the gap narrowing near the end of the decade.
Another factor is the trend towards more and more electronics and power circuitry in electric vehicles and less metal and plastic work. Replacing the brushed motor’s commutator with circuitry was only the beginning. The recent interest in switched reluctance motors is based on the fact that they have no permanent magnets and usually no rotor windings. However, our interviews revealed that they can need twice as many silicon devices in the sophisticated circuitry used to optimise their performance and quietness, so the system does not necessarily end up lower in cost.
There is one certainty though; we were repeatedly told that design of motor controllers is in short supply, mirroring the situation with most of the burgeoning amount of circuitry in electric vehicles, often combined with integration issues too. For example, there is a trend to make gearbox, motor controller and motor in one unit.