There are numerous applications in which it is necessary or desirable to impart a torque to a member without
having to make physical contract with it.
Examples of this include the activation or operation of devices in sealed containers. Permanent magnet couplers
are employed for non-contact transmission of forces and torque.
[9]. Permanent magnet couplers have added advantage of torque limitation in critical applications to avoid mechanical
failure due to torque overloads.
The torque transmission for these applications usually entails some form of magnetic coupling.
The operation of this device is straightforward.
Specifically, each magnet is constrained to rotate about a common central axis.
There are two types of permanent magnet couplers i.e. axial (Face) and coaxial (concentric) types.
These couplers are finding wide use in seal-less pumps, process and chemical indusmes and other such applications where the driving and driven parts are separated by mechanical wall.
Due to the wide spread availability of rare-earth magnets, the present generation of couplers results in a few advantages: i.e. Minimum space and size.
Larger air gaps possible and no risk of demagnetisation.
Fig. 6 shows the cross section and the magnetic flux distribution in a coaxial and face couplers.