Magnets to replace mechanical gears
Mechanical gears generate noise and require lubrication as they suffer from inherent friction that reduces their efficiency. Magnetism, which has been widely used in devices ranging from electrical motors to medical imaging, provides an attractive alternative. Magnetic gearing promises precise torque transmission and improved reliability with little need for maintenance. Scientists working on the EU-funded project MAGIM (Magnetically geared induction machines) have been leading the research on magnetic gears. They artfully coupled a wound rotor induction motor to a magnetic gear. This way a high-torque and low-speed drive system was achieved with extended torque transmission capabilities. Specifically, a rotating diode rectifier electrically links the wound rotor and a boost winding to the gear increases the torque transmission. This new topology has two important advantages compared to more conventional solutions proposed in the past. The torque transmitted to the low-speed rotor is not limited by the magnets, which could be relatively small and light. The results of the first investigations on such a magnetically geared induction motor at 100 kilowatts and 120 rounds per minute were particularly promising. A torque increase of about 15 % was obtained while the torque density transmission exceeded 80 Newton metres per litre, opening the way for practical application in power and electricity generation.
Keywords
Mechanical gear, wound rotor induction motor, magnetic gear, power, electricity generation
