Improving electric motors to hugely reduce emission

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Near Tokyo, researchers are studying the feasibility of powering electric vehicles using coils installed in roads. This would reduce the need for heavy, resource-intensive vehicle batteries.

Electric motors help to turn electrical energy into mechanical energy in a huge range of the world’s machines — from cars, industrial robots and escalators, to home appliances, such as refrigerators and vacuum cleaners. As a result, these devices consume more than 50% of the world’s electricity.

Electricity demand is also set to surge with the rise of electric vehicles — and also the need for more industrial cooling linked to climate change — says Kan Akatsu, a motor and generator expert from Yokohama National University in Japan.

The Institute of Electrical Engineers of Japan-Industry Applications Society (IEEJ-IAS) is now actively working towards curbing emissions linked to electrification by uniting experts from Japan’s huge manufacturing and electronics industries, and academia (see box).

The society’s working groups, conferences, and solutions-focused journal, all support sustainable innovation, says Akatsu, a member of the IEEJ-IAS Technical Committee on Rotating Machines. These innovations include “advanced motor-related technologies that contribute to the rapid dissemination of energy-saving products worldwide,” he adds.

Cool innovations

One example of the kind of impact the IEEJ-IAS has been able to foster is the spread of air conditioner inverters, which optimize electric motor speeds by controlling power input.

Most electricity use in air conditioners occurs when their electric motors turn on and off. In the year 2000, researchers from Daikin — one of the world’s largest air conditioner manufacturers, based in Osaka, Japan — presented their findings at an IEEJ conference on a method to reduce air conditioner reliance on this on-off process using inverters.

Simpler circuits (bottom, at right) than existing circuits with separate inverters (bottom, at centre and left) enabled more efficient air conditioners (top). Credit: Yuruphoto/iStock/Getty (top); Daikin Industries, Ltd.(bottom)

Since then, Daikin has introduced inverters into some of their products. These save power by controlling electric motor operation to maintain a set temperature, rather than continually cooling.

Early inverters required large, expensive components such as electrolyte capacitors to smooth voltages, limiting adoption, explains Akatsu. At the IEEJ conference, Daikin proposed a simple circuit configuration that enabled the use of smaller, cheaper capacitors.

Using cheaper inverters and power-saving permanent-magnet synchronous motors, Daikin has produced air conditioners that use 30–40% less energy annually. By 2017, energy-efficient inverter driven models had 94–100% of the market share in Japan, Australia and Europe, Daikin researchers reported in the IEEJ-IAS’s journal, IEEJ Journal of Industrial Applications (JIA)1.

Another important advance highlighted in a 2023 JIA study has been in servo motor technologies2. Servo motors — found in power tools, industrial robots and many other electric devices — help rotate and push machinery parts with ultra-high-precision.

Yaskawa Electric, a leading manufacturer of electric parts, headquartered in Kitakyushu, Japan, have developed a process to control vibration-causing electricity load fluctuations in servo motors. This shortens the time needed for a servo motor-mounted part to settle from 125 milliseconds to 40 milliseconds2.

With demand for servo motors also surging as part of an increasing demand for high-performance electronics, “cutting even small idle times could lead to a significant power reduction for an entire factory,” says Hiroshi Fujimoto, a motion control expert from The University of Tokyo, who also works on the IEEJ-IAS’s Technical Committee on Precision Servo Systems.

Getting good mileage

The IEEJ-IAS and its journal also actively support efficiencies in the rapidly growing electric vehicle (EV) sector.

In 2021, for example, a silicon carbide device that improved the efficiency of the electric motors driving one of Japan’s bullet trains was detailed in a paper in JIA3. The silicon carbide device enabled the Central Japan Railway Company to halve the motor’s power conversion system size, reducing its weight by 20% and electricity use by 6%.

Another set of important transport innovations described in JIA involves Toyota Motor’s Prius, the world’s first hybrid electric vehicle — powered by both gasoline and electricity. Advances in the vehicle’s electronic components — motors, inverters, and batteries — improved its fuel efficiency by 36% between 1997 to 20154.

Lessons from this vehicle should now also be applied to EVs and fuel cell cars, adds Junichi Itoh, an expert in power electronics from Nagaoka University of Technology, who works on the IEEJ-IAS’s Technical Committee on Power Converters.

Efficient EVs that harness renewable energies could greatly reduce transport emissions from fossil fuels, agrees Fujimoto. But EV sales are still being limited by the cost of lithium-ion batteries and short mileages, he adds.

While larger batteries could increase an EV’s range, vehicle prices would rise and more rare metals would be required to make them, he says.

Some IEEJ-IAS members argue that an innovative way to address this problem is with wireless power transfer (WPT) systems. These use power-transmission coils installed in roads to send electricity to EVs in motion, rather than requiring batteries to store large amounts of power on board. “Using WPT systems for power means EV batteries could be less than a tenth of the size of current batteries,” says Fujimoto.

In JIA, his team’s modelling shows that one type of WPT system could reduce EV greenhouse gas emissions by about 34% compared to EVswith large capacity batteries5.

Now in a suburban city near Tokyo, Fujimoto and his collaborators are collecting feasibility data to help them build a real-world WPT system.

The impact of this innovation, and many others being supported by IEEJ-IAS networks, could be significant for emissions, Fujimoto says. “If EVs becomes cheaper, lighter and smaller, that would be a huge step toward carbon neutrality,” he says.

The Institute of Electrical Engineers of Japan-Industry Applications Society (IEEJ-IAS), headquartered in Tokyo, Japan, is a membership corporation for scholars and corporate engineers. Since 1987, the IEEJ-IAS has promoted the research and development of electrification-related technologies, electric machines, power electronics and motion control.

Today, it has 5,700 members and 14 technical committees. Each committee features study groups that implement in-depth investigations into technologies associated with issues such as carbon neutrality and the Sustainable Development Goals.

The society’s English bimonthly journal, IEEJ Journal of Industrial Applications (JIA), also promotes carbon efficient technologies, particularly those that are commercially successful, with nearly 40% of the papers published in 2024 featuring corporate engineers as authors.

The IEEJ-IAS organizes international events to further its mission, including the upcoming international power electronics conference, IPEC, which will be held in Japan in 2026.

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Focal Point: Sustainable Electrical Innovations in Japan