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Dyson`s `turbocharged` SR motor can phone home

01 June, 2004

Dyson`s `turbocharged` SR motor can phone home

The innovative British appliance manufacturer Dyson has developed a novel switched reluctance (SR) motor which it describes as the first ultra-high-speed SR motor to exploit turbocharger aerodynamics and aerospace materials. It compares the development to the step change from propellers to the jet engine.

For the past eight years, a team of electrical, mechanical, electronic, aeronautical and software engineers at Dyson has been working on the 100,000 rpm machine. The result is a square-core motor (shown above with its impeller in an exploded vew) with a built-in controller which manages energy consumption and provides soft-start and diagnostic functions. It also stores data on the motor and its use, which can be sent to Dyson service personnel, either by holding a telephone handset to the appliance containing the motor, or via the Internet.

The first product to use the new Dyson Digital motor is a compact vacuum cleaner which has gone on sale in Japan this month. With a price-tag of •70,000-80,000 (£344-393), this is one of the world`s most expensive domestic vacuum cleaners, but Dyson argues that the benefits justify the price. The powerful cleaner weighs less than 4kg and measures less than 200mm x 250mm x 300mm.

"We wanted to overcome the problems associated with existing motors - specifically brush, commutator and magnet failures," says Simeon Jupp, Dyson`s director of research, design and development. "The motor has its origins in switched reluctance motor technology, but with its speed, size and diagnostic capabilities, it takes the science to new levels. It has the potential to be the brain and brawns behind Dyson innovations of the future."

Dyson claims that the motor is the fastest ever developed for domestic appliances - up to three times faster than conventional vacuum cleaner motors - but it is much smaller and weighs around 1kg, compared to the typical 1.3kg. It also generates 400 Air-Watts - a measure of the "suck" in vacuum cleaners. This is about a third more than conventional motors.

The 100,000 rpm motor spins more than five times faster than a Formula One engine, and has a similar power-to-weight ratio. The control system pulses the motor with energy four times per revolution, requiring more than 400,000 signals, decisions and pulses every minute.

The motor`s impeller is made from a carbon-fibre-reinforced material called Peek, which is more usually found in applications such as jet fighter wings. Its blades curve continuously in all three dimensions, with hardly any straight 2D sections - most previous impellers have had straight sections towards the exit, even in high-tech aerospace applications.

The impeller tips spin at close to 1,000km/h, with a clearance of just 0.3mm between the blade tips and the housing. Dyson worked with a bearing manufacturer to develop the motor`s tailor-made high-speed bearings. During development, the company`s engineers halved the weight of the rotor, resulting in a rotating assembly (shown above) that weighs less than 100g. By comparison, the image below shows a rotor, commutator and impeller from a conventional vacuum cleaner motor.

Dyson predicts that the motor will have a working life of more than 1,000 hours of constant use - compared to the 600 hours before the brushes wear out on a conventional appliance motor.

Although the motor was developed in the UK, it is being manufactured in Malaysia. Dyson is planning to apply the technology to other products. There are no plans at present to sell the motor to external customers.

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