EVs go all-wheel drive
2016年12月9日 Dr Peter Harrop
Jaguar Land Rover wants half its cars to be available in an electric version by the end of the decade, after showcasing its first electric car at the Los Angeles Auto Show earlier this month. It wants to build electric cars in Britain in what would be a further boost to the UK automotive sector after the Brexit vote. The Indian-owned carmaker built just under a third of Britain's 1.6 million cars last year and has just showcased its first electric car, which will be built in Austria. I-PACE is a sporty crossover, in keeping with the brand's image. The five-seat vehicle employs two electric motors, one for each axle, with a combined output of 400-hp and 516 pound-feet of torque meaning blistering 0-60 mph in four seconds - matching the high-performance Jaguar F-Type SVR sports car. This is in line with the technology roadmap of the new IDTechEx report, Electric Car Technology and Forecasts 2017-2027.
The sophistication of motor design and deployment in cars is now in some contrast to battery application where Tesla, GM and others currently achieve double range by little more than stuffing in twice the amount of battery meaning suffering twice the trading losses. The big story is not therefore whether battery costs will drop fast enough to prevent some motor manufacturers running out of re-investment. It is how power electronics with motors are expanding in form, function and integration, this boosting everything from performance to economy and the speed of progress towards energy independence. Some of this is even a work-round for the battery problem. For example, in-wheel motors with integrated brakes and motor controllers can increase range by 15%. Wide bandgap semiconductors in motor controllers can reduce or eliminate the need for water cooling and work more efficiently increasing range by 8%. The effects are multiplicative.
The move to multiple electric motors, at least one of which may be axle-mounted, may eventually include 48V mild hybrid cars and light commercial vehicles coming in in a big way in 2017. They will eventually transition to being true electric vehicles by having brief pure electric, engine-off modes such as take-off, creeping in traffic and active cruising made easier with dual drive. Nick Pascoe, CEO of CPT, a leading developer of the motor-generators at the heart of that technology, sees them starting as one per vehicle, an example being the engine-integrated starter generators appearing in the Mercedes S Class in 2017, then, in some cases, adding an axle mounted motor generator that does not perform the starter function but optimises traction and performance. One way or another, two or three motors per vehicle is becoming a very popular format in cars, industrial and commercial vehicles. See the new IDTechEx report, Industrial and Commercial Vehicles on Land 2017-2027
In-axle motors are coming in even when only one traction motor is used and this is part of a bigger picture spanning light commercial vehicles and even large industrial vehicles though here we see great interest in near-wheel motors with no axle and to some extent in-wheel motors. Whereas batteries are stuck with lithium-ion technology for the coming decade, even as motors proliferate, there remains a healthy contest between asynchronous (AC induction), switched reluctance synchronous, permanent magnet synchronous and intermediate options. For example, a synchronous reluctance and a PM motor are the basis of IFEVS four wheel drive microcars in Italy. Asynchronous was considered to be the big, reliable but poorly performing and relatively inefficient "washing machine" option but they are standard on Tesla cars with ludicrous mode, a Canadian performance motorcycle announced this year, Continental boost starter generators for 48V mild hybrids and in an increasing number of other vehicles, particularly buses.
The motor technology contest shows that there are many more gains to be made with motors and related power electronics. The IDTechEx reports Future Powertrains 2016-2036 and Electric Motors for Electric Vehicles 2017-2027 (forthcoming) and give the detail. We are moving on in both format and location from Toyota's Aisin making sophisticated transmission-integrated motors and motor-generators for the successful Prius. For example, Dana's new e-axles for electric transit buses and city delivery vehicles launching in 2018 will feature a fully axle-integrated motor and gear box sold as one item. They will supply appropriate product whether one or both axles are electrically powered in this way. Fuel economy is one gain from dispensing with heavy in-board mechanical drives in this way. Several percent: another multiplier.
Top image: Jaguar F-Pace, Matthew Lamb, Wikipedia