Seeing the future of electric motors for electric vehicles

By definition, an electric vehicle is driven by an electric motor for some or all of the time and these are becoming more sophisticated and multipurpose and there are more per vehicle. By contrast, the battery remains nothing more than energy storage; it is becoming smaller and increasingly abandoned all together. For example, supercapacitors or fuel cells sometimes replace or partly replace the battery to give longer life, longer range or better performance and sometimes there is no energy storage at all.

New EV end game

As described in the IDTechEx reports, “Energy Independent Vehicles 2016-2026” and “Energy Independent Electric Vehicle Technology Roadmap 2016-2036” the end game is EIVs – energy independent electric vehicles, some with no energy storage. You can even buy ones that wake with the daylight, being propelled solely by the electricity they make on-board from sun. Others use wind, waves and so on but the common factor is sophisticated motors, one Dutch solar car having a record-breaking 97% efficient motor, so efficient that the car donates electricity to the grid as well as doing its task of carrying several passengers around. On-road, off-road, marine craft and solar planes aloft for five years need motors that work on minimal power with minimal weight. They must be small too because aerodynamics and, in the water, drag matter crucially so the vehicle must be compact and streamlined. To see the future look at Formula One racing, Formula E racing, the latest supercars and, yes, those EIVs.

Much more than a motor

Let us call EV traction motors rotating electrical machines (REMs) to encompass those having many functions beyond traction. The jargon is confusing but they embrace simple traction motors to multifunctional devices in 48V mild hybrid cars, vans, trucks and maybe buses from 2017 onwards. First will be cars followed by 48V MH vans and trucks.  They incrementally improve traditional powertrains as the lowest cost, easiest way for an automotive manufacturer to upgrade his C and D size cars – maybe more - to meet the tough emissions regulations of 2025 and 2030. Paradoxically this simplicity is provided because the electric motor becomes the most complex one yet, doubling as starter motor, engine booster so the engine can be downsized and traction motor in up to four different pure electric vehicle PEV modes. It is also a generator producing four times the current of the old alternator and it has a punishing duty cycle. The result is a vehicle with most of the attributes of a strong hybrid that does not plug in and half the cost. It may largely replace them, not just the traditional ICE powertrain with its increasingly illegal emissions.

Puzzling jargon

These devices are sometimes called boost recuperation machines and they start as belt driven starter generators (BSG) and evolve to be within various parts of the powertrain as integrated starter generators (ISG). Some see a big future for these 48V mild hybrids in buses but few see much scope for them in marine vessels or aircraft according to IDTechEx research this year. The time window for 48V mild hybrids was put at about 15 years by most vehicle and device manufacturers and developers, with very large sales during that time. For more on the evolving technology and the huge potential of 48V mild hybrid and the REMs at the heart of them read the new IDTechEx report, “Mild Hybrid 48V Vehicles 2016-2031”.

Simpler motor generators

The more-powerful, high-voltage motor generators and traction motors for strong hybrid and pure electric vehicles are improving rapidly. Progress can be often be seen first in racing and supercars with permanent magnet motors of superlative performance from Yasa and others. They had more than one per vehicle to give efficiency, redundancy, vectored steering and traction and so on. Now, from Tesla to Mitsubishi, electric cars have two motors per vehicle. It will not stop at that. Led by military vehicles and BYD large buses, for example, some of those motor pairs are going in-wheel, integrated with their control electronics. Proton of Malaysia has developed such a car in affordable form. In-wheel REM manufacturer Protean Electric has first successes. Protean is a technology company that has developed an in-wheel, electric-drive system for hybrid and pure electric light-duty vehicles. Their technology creates a permanent magnet e-machine with relatively high torque and power density with the power electronics and controls packaged within the motor itself.

Lessons from supercars

We can glimpse what comes next in some regular vehicles by looking at four new supercars announced this year, all with three or four REMs to all four wheels. For example, the Honda Acura 2017 NSX with its Sport Hybrid Super Handling All-Wheel-Drive (SH-AWD) system has the water-cooled direct drive motor (DDM) connected directly to the crankshaft. This provides instant power to the rear wheels and helps "torque fill" the void until the turbochargers and engine get into their sweet zones. Others replace the turbocharger with an instantly optimal electric supercharger using the ample current from a high power REM and large energy storage.

Capable of developing 35 kW/ 47 hp at 3000 rpm, the water-cooled Acura DDM unit, connected directly to the crankshaft, provides Tesla-like acceleration but also doubles as the starter motor and charges the lithium-ion batteries. Similar in concept to Porsche's 918 and McLaren's P1, the NSX's twin motor unit (TMU) not only provides added instantaneous e-power for launch but also adds torque vectoring – optimal power to each wheel at all times. Additionally, a TMU is located centrally between the front wheels, each of these REMs being capable of developing 26.5 kW/ 36 hp bringing the total power for the complete hybrid system to 421 kW/ 573 hp.

An industry resurgent

There are huge opportunities for motor manufacturers in future: little wonder that Borg Warner bought Remy and all Tier One suppliers are looking to get more involved. Continental will be looking for more companies like its excellent Zytec acquisition that pioneers very advanced REM tecchnology.

Redefining the product

The value growth of the value market for traction REM systems in vehicles will particularly lie in integration and expansion of device capability. For example, the key to a switched reluctance machine is not the very simple metalwork, compact, rugged and lowest cost. It is in the necessarily more-sophisticated controllers as they power John Deere agricultural strong hybrids down to some of the planned 48V mild hybrid cars.

Problems that are opportunities

How do we integrate flywheels with their own generators to REMs? How do we minimise the power to weight ratio of the whole propulsion REM system in the new electric aircraft and boats? Is IFEVS in Italy right to design propulsion units common to land, water and airborne vehicles? Is it one business? Can superlative efficiency translate into minimising or abandoning heavy, costly, bulky oil or water cooling in some cases? Where will the trend to less REM metalwork and more electronics go next? How do we best avoid the price hikes and temperature and stability challenges of permanent magnets in REMs? From Siemens to Continental, are those using asynchronous (AC induction) REM technology in buses, road cars, golf cars and forklifts on the right track? These challenges mean business.

Structural electronics and integration

The IDTechEx report “Structural Electronics 2015-2025: Applications, Technologies, Forecasts” spells out how the age of components-in-a-box is coming to an end as the wheel or propeller become the motor-generator, energy storage and more. The bodywork of the vehicle becomes the circuitry, energy harvesting and energy storage doubling as load-bearing structure. Often it becomes a smart materials play, again altering the supply chain radically. A motor in a case wired to a controller in a box wired to other boxes? No more. 

Increasing percentage of increasing market

There are opportunities to sell REM systems at premium price and others to sell in volumes of tens of millions yearly. In an increasing percentage of cases, these proliferating, increasingly capable systems will take a higher percentage of the cost of the land, water and air vehicle. NASA is even looking at arrays of propellers each with its drive motor along the full length of the aircraft wing. The Protean in-wheel motor for land vehicles is in-effect several motors in one in order to give redundancy – little chance of a catastrophic failure. The traction REM systems business value is set to grow very rapidly indeed. It will take a significant share of the EV business as that grows to nearly one trillion dollars in ten years on IDTechEx analysis of 46 categories. This figure is boosted by the new 48V mild hybrids as they become EVs and later EIVs and other powertrain innovations all with their own very special REM requirements.