Electric vehicle motors: a business in turmoil
Okt 11, 2011 Dr Peter Harrop
In this article we share some of our research for the new IDTechEx report, Electric Motors for Electric Vehicles 2012-2022. Today, the motors that propel electric vehicles on land, through water and in the air are mainly brushless because brushed commutator motors are on the way out. Most of the number and the value of those brushless traction motors lies in permanent magnet synchronous ones, notably Brushless DC "BLDC", a form with trapezoidal waveform, and Permanent Magnet AC "PMAC", a type with a sinusoidal waveform. No matter: they both have excellent performance including simple provision of reverse and regenerative braking. However, that dominance is about to change. The main reason is not those well publicised but elusive in-wheel motors coming in at two to six per vehicle but simply the move to much larger vehicles and therefore motors.
Small vehicles today
At present, half of the money spent on traction motors for electric vehicles concerns very small vehicles such as tiny SolTrac agricultural vehicles, mobility scooters and power chairs for the disabled that are so popular in Europe and the USA, mobile robots in the home in Japan and "walkies" meaning pedestrian- operated golf caddies very popular in Japan, stair walkers, motorised lifters, sea scooters that pull the scuba diver and, of course, those hugely popular two wheelers in China with 34 million e-bikes alone sold worldwide in 2011. Add tiny quad bikes, All Terrain Vehicles ATVs, go-karts and golf cars and their derivatives. 92% of electric vehicle traction motors are currently needed for those small vehicles and they are therefore sold substantially on price.
Big vehicles tomorrow
In a huge change in mix in the electric vehicle market and therefore the electric motor market, those small EV motors become a mere 25% of the electric vehicle motor market value in 2022 as the big vehicles, and therefore big motors, become very successful. For example, the value of the market for military electric vehicles increases over 20 times as military forces buy battlefield hybrids rather than just small pure electric runabouts. The bus market value rockets nearly seven times as China, in particular, buys huge numbers of large hybrid versions as part of its national transportation plan. Better reported is the burgeoning electric car market where hybrid versions in particular are behind a nearly six fold growth in market value over the coming decade. All this turns the world of traction motors on its head.
Different motors needed
The electric motors that are required for the bulk of the market by value are becoming much higher in power and torque. For example, an Autonomous Underwater Vehicle AUV - like a torpedo but making its own decisions - can push from a huge battery of up to 400 kWh (eg Monterey Bay Aquarium Research Institute), a large forklift or bus delivers 250-350 kW per motor but cars typically need up to 70kW per motor with a low-cost electric bicycle merely offering a 0.25 kW motor. At the large end, torque from the traction motor is up to 6000 Nm yet only 0.2 to 0.5 Nm is needed by many two wheelers and mobility vehicles for the disabled. The heavy end is territory where the asynchronous motor is winning now that its performance has improved and the cost of the control electronics has been got under control. For example, the Heavy Industrial category refers to heavy lifting as with forklifts and mobile cranes and here IDTechEx finds that 89% fit asynchronous motors otherwise known as AC induction - brushless traction motors with no permanent magnets.
Around 63% of military vehicles and 52% of large buses fit asynchronous motors on our analysis of 212 electric vehicles, past, present and planned. Toyota, world leader in electric vehicles by a big margin, is using asynchronous motors for its forklifts and buses and has now developed them for possible use on its cars, which currently use permanent magnet motors.
Nonetheless, we must be very careful about sweeping generalisations. Many experts believe that asynchronous motors will sweep the board at 5kW power upwards. That is tantamount to saying that they will take over 70% of the traction motor market value because there are even 5kW motors in golf cars, on motor bikes (eg MotoVolta, LLC) and the smallest leisure boats and leisure submarines (eg Silvercrest Submarines). Although the enthusiasts can point to such motors used today in golf cars variants as one example, it is important to observe the very rapid improvements in synchronous motors including taming the noise and vibration of the switched reluctance synchronous motors that need no expensive magnets. IDTechEx does not accept the conflict as one primarily between those using expensive neodymium magnets and those with allegedly lower inherent costs. In the larger electric vehicles performance matters more than cost and anyway, asynchronous motors use a lot of expensive copper and control circuitry.
Performance matters more
The winners in future traction motor markets will win on performance more than price, this including very different criteria in different vehicles with many problems still to solve. For example, Boeing has a contract to develop an Unmanned Aerial Vehicle UAV that can stay aloft for five years. It has subcontracted Newcastle University in the UK to create a traction motor with several times improvement in power- to-weight ratio in order to make this possible. NASA's dream of small aircraft taking off purely under the power from in-wheel motors may call for new motor designs as will the thunderbolt of power from regenerative braking of landing airliners that then become electric vehicles while on the ground. Fault tolerant motors are needed in other applications and while Chorus Motors has developed an asynchronous one, Protean Electric has announced an equally impressive synchronous one. Reducing or eliminating the need for water cooling is a welcome advance as yet rarely on offer with large motors. Working at the more efficient high voltages of 300-700V means less copper, thinner, more manageable wiring and less power wastage. Not all motors meet these requirements.
In-wheel motors not as portrayed
We fear that only 2.5% of electric vehicles by land, water and air will have multiple traction motors in 2022 and that may mean only 5.6% of traction motors sold will be for multi-motor vehicles - mainly in-wheel motors for land vehicles. That is big enough for two or three suppliers to make enduringly profitable, substantial businesses out of supplying them but it is not a primary route to leadership in the overall traction motor business. Of course, in-wheel motors for single motor vehicles, notably two wheelers will be separate from that and even more successful than they are today, maybe over 100 million of these being sold - largely on price - in 2022.
While there are a few asynchronous in-wheel motors, nearly all of the sales of in-wheel motors concern the usually smaller synchronous versions, so let us now look more closely at the glamorous world of in-wheel motors, already a huge success in e-bikes, selling by the tens of millions. Here a warning comes for Mitsubishi deciding not to use its in-wheel motors in its best-selling MiEV pure electric car because of cost. Currently you cannot have several motors for the price of one when you want to adopt in-wheel power. While motor manufacturers hope that a price premium will be on offer where they eliminate transmission and differential, there are problems of ride to finance and concerns at Fiat, for example, about wheels jamming.
Wake up time
It is wakeup time for the electric vehicle traction motor industry. Our survey of 123 manufacturers shows far too few making asynchronous or switched reluctance synchronous motors and larger, high power, motors with strong traction or even exceptionally light weight powerful motors. There are far too many making traction motors with brushes. In short, this is an industry structured for the past that is going to have a very nasty surprise when the future comes. Most of it is not even talking to the vehicle manufacturers that will spend most to buy traction motors in the years to come. Many think easy money comes from pursuing the obvious, notably selling to the fearsomely competitive electric car market where 90% of your customers are headed for insolvency. In China alone, there are over 100 manufacturers of electric cars and none are successful.
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