Electropermanent magnet



Electropermanent magnet - a type of electromagnetic device which uses a combination of magnetically soft (e.g. iron), semi-hard (e.g. Alnico) and hard (e.g. Nd-Fe-B). Electric current is used to change the level of magnetisation of the semi-hard part. Once the magnetisation is changed the state is stable and no electric energy is required.

Changing the state of the semi-hard part results in changes of the external magnetic field generated by the whole structure. This can be used for generating mechanical forces due to attraction or repulsion between magnetised parts.

Because relatively low average power is required for the operation of the device (only pulse switching) such actuators can be used as miniature actuators in small-scale robotics (a few millimetres in size).

On the other hand, the fact that no electrical energy is required during passive operation the devices has some inherent safety implications. Lifting very heavy load (up to 40 tons) without danger of dropping the load when the supply of electricity is cut off (unlike ordinary lifting electromagnets) is possible.

In large devices during normal operation the electrical energy used is less than 5-10% as compared to conventional electromagnets.

The technology was invented in 1960's.