26.4.3 Electro-Permanent Magnets

An electro-permanent magnet is one where an electrical current passes through a coil enclosing magnetic material. A pulse of electricity creates a permanent magnet, the polarity of which can be created either way. There are no moving parts and the electric current is only required to create the magnet, not sustain it. Changing the polarity of this magnet has the same effect as the mechanical movement within a permanent magnet thereby causing it to add to or cancel out the field of the static magnets.

If the degree of magnetisation is controlled, the magnetic lifter can be partially magnetised, providing the facility to shed excess load then fully magnetise to secure the remaining load.

The electrical energy may be supplied via batteries (small magnets) or mains power (larger magnets).

The unit shall provide a tear off force of at least 3 times the working load limit under the conditions specified by the manufacturer. An indicator should be fitted to show when the magnets are magnetised and for magnets with variable power it shall distinguish between full and partial magnetism.