Cheaper motors offer higher efficiency

A range of motors could be made more efficiently – and more cheaply – thanks to a new magnetic material. Lou Reade reports



Swedish researchers have designed a motor, which they claim would be twice as efficient – and half the cost – of existing devices.
The innovation centres on a new type of magnetic material, coupled with production methods that slash the number of components and reduce the cost of assembly.
The implications are far-reaching and could mean that any device that relies on motors – from a washing machine to a car – could be produced far more cheaply.
The researchers, at Lund University’s Centre for Electro-Magnetic Conversion (Cemec), have spent 15 years creating ‘plastic bonded iron powder’ – in which metal particles are ‘suspended’ in a plastic material. This compound is used to produce motor components using a technique called ‘centrifugal moulding’.
“The development started with injection moulding of low performance motors,” says Tord Cedell. “We found that new, alloyed powders with very well defined shape and grain structure would give high packing ratio and low losses. Experimenting with other techniques, we understood that a special form of rotational moulding [centrifugal moulding] gives superior properties and high production throughput.”
The energy efficiency of conventional electrical actuators – including motors, inductors and transformers – can be boosted by incorporating a laminated core of soft magnetic iron sheets, he says. Cemec proposes to replace the laminated sheets with a single moulding of ‘soft magnetic composite’. As well as being more efficient, it would be made in just “a few” production steps rather than the 60 that it currently takes, says Cemec.
The likely list of benefits from using this approach includes: reduced size and weight (as the actuator and driven object are integrated, minimising the need for gearboxes or flange couplings); reduced energy consumption (with fewer mechanical parts); and reduced cost (with modular design allowing for cost-effective automated production – so suitable for high labour cost economies).
The Cemec team is already producing inductors, transformers and induction heating coils using the technique – but full-blown motors will take a little longer.
“For mass production of motors and generators, it will be – depending on financing – at least one more year,” he says, noting that Cemec is currently seeking venture capital for this development.
The technique is not aimed at high-performance motors such as servo motors, but could easily be used in products such as torus, claw-pole and transversal flux motors.
“We see it being used in all sorts of motors and generators that work at high electrical frequencies,” says Cedell.
He says that the new material – and the new design – will make high frequency losses negligible, give low permeability and have a high thermal conduction between coil and magnetic flux conductor material.”
He points out that the material alone does not have a magic effect on a conventional motor design.
“Just changing the material in a conventional design would result in a poor motor,” he says.
Cemec also accepts that commercial examples of ‘SMC motors’ are already being used – such as a motor that supplies oil to an advanced braking system in a Japanese car. But it adds that these are low volume applications – and its aim is to make the motors in high volume.
The work was funded with SEK 12 million (£1 million) over five years from Vinnova, the Foundation for Strategic Research (SSF) and venture capital company Industri Kapital. A patent was issued in October.
Research such as this is important to Sweden – and, by implication, other high economy countries.
“[Researching this field] is strategically important for Sweden,” says the organisation. “[We rely] on innovative design, efficient production and high energy efficiency of products for industrial competitiveness.”

Alloy makes motors more efficient

Across the pond, researchers at the Iowa-based Ames Laboratory have developed a permanent magnet alloy that will retain its properties at high temperature.
This should allow the production of electric drive motors that are more efficient and cost effective.
Iver Anderson, Ames Lab senior metallurgist and Iowa State University adjunct professor of materials science and engineering, said that future 'ultragreen' vehicles such as fully electric cars, fuel-cell automobiles and plug-in hybrids will rely on this kind of technology.
“They all have electric drive motors, so that’s a common theme,” he said. “It’s important that those motors be made economically with an operating envelope that fits how they will be driven. The automotive companies in this country have set out a series of parameters that they would like electric motors to meet.”One of these is the need for permanent-magnet electric motors to operate well at temperatures up to 200°C.
“That raised a lot of eyebrows for people who know anything about magnets,” said Anderson.
Most types of permanent magnet lose a lot of their magnetic energy at modest temperatures and operate at less than half their power by the time they reach 100-125°C. This new breed of magnets would operate with good magnetic strength at 200°C, thanks to an alloy that replaces pure neodymium with a mixed rare earth.
The alloy exists as a fine powder which can be processed by injection moulding – which Anderson says will be crucial if it is to be adopted by the automotive industry and its need for high volumes.
“Currently, each magnet making up the magnet array in an electric motor is glued in by hand,” says Anderson. “That’s fine for small runs of 50,000, but try doing that for the millions of cars with electric drive motors – one for the front and one for the back – that consumers will want to buy in the next 10 years. It’s not going to work.”
The work is part of the US Department of Energy's Vehicle Technologies Program, which aims to develop more energy-efficient and environmentally friendly transportation technologies in order to cut the use of fossil fuels.

Author
Tom Shelley

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