Feb 23 2006
Rotary tools will need increasingly high speeds in the future, for example, for drills used in medical technology or spindles used in machine tools. To drive these tools directly and efficiently requires an ultra-high-speed electrical drive system. Today, industrial motors achieve maximum speeds of 250,000 revolutions per minute, but researchers at ETH Zurich have now developed a drive system which achieves speeds of over 500,000 revolutions per minute, generating 100 watts of drive power and is not much bigger than a box of matches. The rotor has a titanium sleeve construction that is capable of withstanding extreme centrifugal forces. A low-loss stator ensures maximum levels of efficiency, and the ultra-compact electronic circuitry is digitally controlled.
The ultra-high-speed drive system is expected to enable further innovative developments and give new opportunities to a wide range of different industries. For example, in portable energy supplies, ultra-micro gas turbines could soon replace the batteries currently in use. Another example would be extremely lightweight turbo compressor systems to increase the efficiency of fuel cells in vehicles.
"The next step we wish to achieve is to increase the speed up to 1 million revolutions per minute", is the goal of Johann Kolar, Head of the Power Electronic Systems Laboratory. A key factor to achieve this increase in speed is the bearing technology. It is hoped that innovative concepts, including magnetic or air bearings, currently being investigated by ETH researchers, will bring the necessary improvements.
http://www.ethz.ch