Electric motors have existed, in various forms, for the best part of 200 years. In an automotive setting, we interact with them multiple times a day – including when we fill up with fuel or turn on the climate control. But, in recent years – and given the acceleration in electrified transport solutions – drivers have quickly come to think of electric motors as the engine of the future.
Of course, this is somewhat true. Comparing today’s car parc with that of a decade ago shows the immense progress that has been made in electrifying personal vehicles. There’s also growing momentum in the commercial vehicle sector. Even in hydrogen fuel cell applications, it’s still a predominantly electric powertrain.
Considering the industry’s progress towards alternative powertrain solutions, it’s easy to only think of electric motors as a direct drive solution. A single-minded approach to electrification poses a barrier to a stepped transition and, in reality, there’s a variety of uses for electric motors that could bring benefits for fleet operators today.
Direct drive is important
Though the above statement may sound contradictory to my previous point, direct drive is still a part of the motor mix. It’s worth remembering that not all electric motors used for such an application are designed equal. Advanced Electric Machines’ (AEM) electric motors are rare-earth magnet free, removing the need to use finite metallic elements in their design. These materials are typically very environmentally damaging to mine and refine – and are also difficult to recycle at the end of a motor’s life.
An alternative approach to electric motor design can also bring benefits beyond sustainable electrification. As there are no permanent magnets in AEM’s reluctance motor design, it doesn’t generate any electrical current when not powered. This means that OEMs have access to a high performing electric motor that is capable of freewheeling – a feature not often found in automotive-focused designs. It’s common practice for drivers of internal combustion trucks to coast whenever suitable as a technique to maximise fuel efficiency. With a magnet-free motor, truck manufacturers have the option to develop a true coasting mode that does not expend any electricity. Operators, therefore, have access to another tool to maximise range and efficiency when on the road.
The benefits of a freewheeling motor also extend to wider vehicle safety. As a permanent magnet machine cannot be ‘turned off’, it can make vehicle recovery a complex task. Care has to be taken to not damage the powertrain with excessive heat – or worse, risk a dangerous failure of the system. It’s typical, therefore, for electric vehicle manufacturers to mandate that their vehicles are recovered on trailers or on dollies. A freewheeling motor removes this complexity altogether, by enabling easy towing capabilities.
AEM’s reluctance motors are highly efficient across a broad performance range – particularly at medium to high speeds. With trucks often sitting at a consistent speed for hours at a time, this benefit can help OEMs to optimise powertrain efficiency and reduce total operation duty cycle energy use.
Rigid hybridisation
The concept of a hybridised internal combustion and battery-electric powertrain is nothing new. It’s commonplace in passenger vehicles and is becoming more common in new HGVs. That said, there are still a staggering number of trucks on our roads that use solely combustion powertrains.
If you’re able to eliminate heavy batteries and use a lighter, short term energy storage solution, EV powertrain componentry can be compact and easy to drop into an existing combustion driveline. AEM’s freewheeling motor forms part of one such truck retrofit KERS solution, using ultracapacitors instead of batteries. The motor serves as both a means of harvesting energy as a generator and as a way of boosting acceleration through the deployment of energy. In testing, retrofit hybridisation has been shown to reduce a truck’s fuel consumption and carbon dioxide output by up to 28% and overall emissions (NOx, PMs and brake particulate matter) by up to 80% in real world trials.
As chassis modifications are not required, the opportunity to hybridise a vehicle is inclusive of most vehicle brands and can be removed and refitted to another vehicle. Bus fleets can also benefit from retrofit hybridisation.
KERS, in this context however, may not be the right fit for everyone. To achieve the most significant savings in this use case, the vehicle needs to be regularly stopping and starting to harvest and deploy the energy. It’s therefore best suited to urban and regional routes, rather than long-distance work.
Drive assist trailers
When it comes to articulated trucks, especially road trains used in different markets or countries, such as Australia, a KERS e-axle system fitted to each trailer can provide a much-needed torque boost to get the vehicle underway.
Instead of being limited by the power output of the tractor unit at the front, operators can use reluctance motor-driven KERS solutions with up to 200kW of energy per drive-assisted trailer (DAT) during initial acceleration. This allows them to increase the available power during start up acceleration and facilitate an increase in payload. The freewheeling capability of the magnet-free motor means that, once underway, it can automatically deactivate and be towed within the driveline without the need to be physically declutched.
Away from road train use, there’s potential for DAT solutions to reduce long-haul route emissions. Other players in the sector are reporting that battery-powered trailers are helping to increase vehicle miles-per-gallon figures.
Auxiliary power units
Commercial vehicles often have a wide range of ancillary devices – some hydraulic, some pneumatic and some mechanical. All need a source of power. In battery-electric vehicles, it often makes sense to use smaller, individual electric motors to drive these systems. This differs from most combustion vehicles, which would use a power take-off (PTO) connected to the engine transmission.
By adopting this approach, operators and manufacturers alike can improve total system efficiency, reduce overall cost and enable more design freedom away from the single sole power source. Smaller, power dense motors, such as the HDSRM150 motor that AEM produces, are perfect for such a job.
