0333 090 7822 27 www.drivesncontrols.com July/August 2023 TECHNOLOGY n RESEARCHERS FROM THE University of Sheffield, working with colleagues from the University of Wisconsin-Madison in the US, have developed an electric motor using 3D printing technology that they believe could lead to more powerful motors that use less material. The prototype motor uses a high-silicon electrical steel that reduces energy losses. It consists of a stator with prongs around which coils are wrapped to create a magnetic field. The biggest difference from traditional stators is that the prongs incorporate an intricate design of thin geometric lines designed to reduce energy losses. Traditional methods for creating motor stators are based on lamination processes using stamped sheets of electrical steel. The laminations are stacked to create stators with tiny ridge lines on the tops of the prongs. This method usually relies on electrical steel alloys containing 3% of silicon, resulting in relatively high losses and low efficiencies. Electrical steel alloys with 6.5% silicon can cut the losses but are more brittle and are less likely to withstand the lamination processes. With 3D printing, there’s no need for tonnes of pressure to be exerted in a rolling process. The 10kW prototype stator was printed with its intricate patterns in less than 20 hours. The researchers believe that the technology could be scaled up easily to reach 40kW, and printed faster using industrial 3D printers. The collaborative project began when Alexander Goodall, a doctoral student in Sheffield University’s Department of Materials Science and Engineering, met Nishanth Gadiyar, a post-doctoral research assistant from UW-Madison, at a conference in 2020. They realised that they had what each other needed: Sheffield had access to the printing technology to make UW-Madison’s expertise in unconventional motors a reality. Goodall designed, developed and manufactured the stator. Researchers at the University of Wisconsin tested the prototype and found that it delivered more torque than they thought possible, using less material. “When you have 30% lower mass, you would expect that your torque would also be lower – but that wasn’t the case,” Nishanth reports. “So, this shows that you know you’re actually going to net torque density improvement in this machine and if we can further improve this, making a more efficient motor, would be a game-changer.” “This project has shown the large potential that additive manufacturing has for electrical machines, with lightweight, efficient structures that have never before been possible using any other manufacturing technique,” Goodall points out. UK-US 3D-printed motor delivers more torque than expected The prototype stator took less than 20 hours to 3D print with its intricate patterns THE JAPANESE manufacturer IHI has built a “breakthrough”prototype high-flux plastic magnet rotor for use in ultra-high-speed motors. IHI says the rotor could produce efficient, lightweight and compact motors that could revolutionise the production, performance and economy of electric aircraft and automotive propulsion systems. The rotors are produced by injectionmoulding molten plastic and powder magnet composites, and casing them in a high-strength carbon-fibre-reinforced polymer ring, to create a structure that can withstand more than 100,000 rpm. The use of injection-moulding techniques reduces the need for machining, cutting manufacturing times and costs. Tests have shown that the performance of the prototype rotor matched or bettered that of rotors in which conventional magnets produce all of the magnetic force. The new rotors could halve the use of rareearths by delivering the same output using magnets that are almost 50% plastic. During the moulding process, a magnetic field is applied to align crystals in the plastic material. This strengthens magnetic forces in specific directions and orientates them to maximise the magnet utilisation efficiency. Plastic magnets could revamp high-speed motors
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