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Researchers Deliver Electric Motor Achieving More than 1M rpm

Researchers at ETH Zürich’s Department of Power Electronics have developed an electrical drive system in cooperation with its industrial partners that can achieve more than 1,000,000 rpm. Up to now, industrially-deployed motors have normally reached 250,000 revolutions per minute.

Top left: entire machine with stator and rotor. Bottom left: Rotor. Right: Power electronics. Click to enlarge. Source: ETH Zürich

The new drive system generates an output of 100 watts and is barely bigger than a matchbox. The rotor construction has a titanium shell that is able to withstand extreme centrifugal forces and the ball bearings are optimized for extremely high speeds.

Conventionally, the higher the rotational speed, the more losses there are. But the researchers from ETH Zürich solved the problem with an especially low-loss stator. Ultra-thin copper wire is used for the windings which are inserted in a cylinder made of special iron previously unused for machines. In addition, the machine is fed by electronics specifically designed for such engine speeds.

The drive system was brought to fruition in collaboration with industry. The machine was manufactured by the German company, ATE GmbH, which specializes in the development of highly efficient electrical drives. The ball bearings came from the company, myonic, which is also based in Germany and has been manufacturing high precision miniature ball bearings for over 70 years. The construction of the whole system, the development of the electronics and the regulation of the drive system, however, was developed at ETH Zurich’s Department of Power Electronics.

Based upon the results of this research, Christof Zwyssig and Martin Bartholet, also a post-graduate in the same department, founded the spin-off company, Celeroton, in August 2008. The company will seek to provide ultra-high revolution electrical drive systems for different branches of industry and areas of application.

Celeroton is set to become a supplier for manufacturers of, for example, fast-spinning drill or milling machines. The trend towards increasingly smaller cell phones and other electrical appliances means that increasingly smaller holes have to be drilled for the electronics. This is only possible using a drive system that boasts a high rotational speed.



About motors/generators:

A Canadian University group have developped a multiple stage (modular) stator-rotor generator on the same shaft that can be electronically varied in size (by connecting or disconnecting stages) to account for wind speed (and potential power) variations.

Over and extended period, the total usable wind turbine generated power was increased by up to 56%.

This type of multi-stage generator is longer but has smaller diameter, less weight and overall wind resistance. The pilot test generator will be followed by a full size (large) unit shortly.

This could reduce the cost of Wind power where wind speed varies a lot, which is the case in most areas.


100 W would be quite sufficient for an electric bicycle!


Several aspects resulting from the remarkably high rpm make this impractical for automotive apps, even a bicycle. The gearing that would be necessary to reduce shaft speed down to a usable range would be highly lossy and consist of many stages, and the electronics required to control the motor whould be highly specialized and expensive. Makes no sense for anything other than applications requiring excessively high rpms, such as the noted high precision machining machines.

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