Electric motor will be the driving force in the near future. Wit fossil fuel drying up as well as becoming a serious threat to the environment and solar power still a long way off it will be electric motors which will rule the roost. Things are rapidly changing in the world of electric motors. What we are seeing today will become obsolete in the next five years as a new generation takes over.
Car enthusiasts have long-obsessed about what is under the bonnet of a traditional car, but in the electric world the motor does not get enough attention.However, that may be about to change, according to Dave Oude Nijeweme, head of technology trends at the Advanced Propulsion Centre (APC), a joint project between the UK government and the automobile industry. Dave says major improvements in motor technology are set to have a profound effect on the performance of electric vehicles in the tears to come.
According to Dave, electrification primarily has three pillars: batteries, electric motor and the powertronics [the power management system].It’s not all about batteries though. They do get a lot of headline news but the motors and the powertronics are the fundamental keys.
Generally, in an electric drive system, a motor converts the stored electrical energy in a battery to mechanical energy. An electric motor consists of a rotor (the moving part of the motor) and a stator (the stationary part of the motor).
A permanent magnetic motor includes a rotor containing a series of magnets and an electricity-carrying stator (typically taking the form of an iron ring), separated by an air gap. Currently, there are three types of electric motors that can be fitted in hybrid or plug-in electric vehicles.
Internal permanent magnet (IPM) motors have huge power density and maintain high efficiency over a significant percentage of their operating range. Practically, all hybrid and plug-in electric vehicles use rare earth permanent magnets in their traction motors. Because of the high costs of magnets and rotor fabrication, these motors tend to be expensive.
Among the other challenges to using IPM motors include the limited availability and high cost of rare earth magnetic materials. In spite of the hurdles, the automotive industry anticipates continuing to use IPM motors in the majority of electric drive vehicles over the next decade.
Induction motors have high starting torque and also offer high reliability. However, their power density and overall efficiency are lower than the IPM motors. They are widely available and commonly used in various industries today, including some production vehicles. However, since this motor technology is mature, it is unlikely that further research can achieve additional improvements in efficiency, cost, weight, and volume for future electric vehicles.
Switched reluctance motors offer a lower cost option and are easier to manufacture. These motors also have a rugged structure which can tolerate high temperatures and speeds. However, they generate more noise and vibration among similar motor designs, which is a major challenge.Additionally, switched reluctance motors are less efficient than other motor types, and require extra sensors and complex motor controllers that increase the overall cost of the electric drive system.
When it comes to making electric cars better, it’s the batteries that engineers talk about the most.But aren’t we going to talk about the motor that actually drives the car?And with new technologies like 3D printing to in-wheel motors (IWMs) that allow a car to spin on the spot, electric motors are sure to be grabbing more of the limelight.
Most electric car motors follow the same basic principles – tightly wound coils of wire interact with powerful magnets to create rotation. But despite a relatively simple set-up, there’s still plenty of room for improvement.
“We all know that the power of a motor increases as its speed goes up. A manufacturer wants to spin it as fast as possible in order to make it as small as possible – but then one gets into the problems of cooling,” says the managing director of British motor manufacturer, Equipmake, Ian Foley.
Equipmake’s solution to this problem is to rearrange the motor’s magnets in such a way so that they’re positioned like the spokes of a wheel.This not only increases torque (the force which causes rotation) but also makes the magnets more accessible, so that cooling water can be run directly over them. The company is also now using additive manufacturing – 3D printing – to improve cooling as well as cut costs.
“Fundamentally, we derive two benefits from additive manufacturing. Firstly, you can integrate multiple components, so you end up with a much lower component count because things that would previously have been bolted together are all in one piece,” says Foley.
And the second thing is the issue of cooling. In order to cool one needs much more effective heat exchanges, and with additive manufacturing one can effectively increase the surface area inside the motor for the cooling surfaces and therefore get much greater cooling potential.
However, other manufacturers are thinking about a more radical shift. In most electric cars, the motor is found on one axle and in four-wheel drive cars there are two motors, one on each axle. But there are certain companies that are working on an innovative design, placing motors in the wheels themselves.
The CTO of Protean Electric, Chris Hilton, says that in-wheel motors improve handling because the performance of each wheel can be finely controlled. Hilton went on to say, “in-wheel motors drag down the overall centre of gravity, reduce weight and optimise weight distribution in the vehicle.” Protean’s technology is being tested by manufacturers of passenger cars, commercial vehicles and even autonomous “pods”.
Another company working on in-wheel motors is Japan’s Nidec, which announced its prototype in the first half of 2019. Nidec says that the motor has a plethora of advantages, not all of them obvious – less noise, for example, thanks to fewer moving parts. But perhaps the biggest advantage is that they create space and the cars using in-wheel motors don’t require a separate motor compartment.
“The electric motor technology is evolving further. The elimination of the drive shafts allows the wheels to rotate freely. It becomes possible to rotate the wheels at 90 degrees and drive to the left or the right, or even rotate in place, instead of just driving forward or backward. This adds another dimension to how the car can move around and makes it easy to navigate narrow spaces.”
APC has set out a roadmap of how it sees electric motors developing and, by 2025, it expects costs per kilowatt to almost halve, while power density to triple.
“For the same amount of power that they generate, the motors will weigh a third as much and be one third of the package size. At the same time, the costs will also reduce,” says Mr OudeNijeweme. The electric motor is all set to change dramatically. I don’t know when exactly that will happen but ten years from now it will be unrecognisable from what we see today, may not be in how it looks – but definitely in how it functions.
Article by – Arijit Nag
Arijit Nag is a freelance journalist who writes on various aspects of the economy and current affairs.
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