Contactless Torque transmission. Magnetic couplings

T he non-contact torque transmission is the subject of two articles:

• [D 3 565] : Magnetic couplings

• [D 3 566] : Magnetic speed reducers

Although the subjects covered are very similar, the two articles can be read independently. Readers may find it useful to refer to the articles on shaft couplings [B 5 800] , elastic couplings [B 5 805] and gearboxes [B 5 640] in the Mechanics treatise.

The two articles on non-contact torque transmission are limited to the transmission of non-contact rotary motion between two aligned shafts, with or without speed reduction. There are other modes of non-contact motion transmission, in particular linear motion, but these are not covered in this article.

This article deals with magnetic couplings. A magnetic coupling enables rotary motion to be transmitted between a drive system and a mechanical load without contact between the two shafts. Torque is transmitted via the magnetic field in the air gap, usually using permanent magnets. Motion can be transmitted through a sealed wall to ensure hermetic isolation between two media, e.g. the product to be processed and the drive system. Compared with mechanical couplings, this solution reduces maintenance, as the system is contactless and therefore wear-free. It is tolerant to axis misalignment and reduces vibration transmission.

This article discusses two magnetic coupling technologies that are among the most widely used in industry and available from manufacturers. These two technologies are based on different operating principles: interaction between permanent magnets for synchronous couplings, interaction between magnets and currents induced in a conductive material for asynchronous couplings.

A large part of this article...