Standard exciter coils are wound with Aluminium conductor rated for class 'H' insulation. Coils are cast into their magnet body with a special resin compound of excellent heat conductivity and thus rigidly fixed in position. If required coils can be furnished with copper conductor. Use of special resins loaded with fillers as sealing compound ensures reliable conduction of heat to the magnet surface, maintaining high magnet performance over long, continuous service.

The permissible relative duty factor is 75%/10 mins. or 60%/10 mins. depending on magnet construction and application.

Magnets for extra heavy duty or handling of hot materials are available on request.

1. * Standard operating voltage is 220 V DC. Rated power input for cold magnets listed in column 2 governs selection of suitable electrical switchgear, rectifier, etc. In continuous service, heating of the exciter windings reduces power input. Permissible relative duty factor is 75%/10 min. or 60%/10 min.
2. * The tear-off forces listed in columns 10, 11, 12 relate to a level solid thick slab and an air gap corresponding to 1/300 or 1/20 respectively of the magnets outer diameter 'd'.
3. * The figure in column 13 for each magnet size represents the permissible load which can be suspended with a standard chain arrangement, taking into account safety requirements. Where loads exceeding these limits are to be handled, please order special purpose chains, quoting the maximum weight to be lifted.
4. * Listed lifting capacity guide values in columns 14 to 19 apply to magnets at service temperature.
5. * Lifting capacities for various types of bulk material listed in columns 16, 17, 18, 19 are average values, which may be exceeded or not be reached in actual duty, since the volume seized in each lifting operation depends largely on type, shape, density, alloy composition, distribution and storage of the material, as well as on the skill of the crane driver.

As the result of extensive investigations and series of measurements, it has now become possible for the first time to understand clearly the relation between lifting capacity of a magnet and apparent density of ferromagnetic materials (such as scrap and pig iron) and express this in a graph.

Each type of scrap has a different apparent density which may vary widely, depending on its origin, even for grades bearing the same classification code. The curves in the above graph permit fairly accurate determination of lifting capacities for various types of scrap the apparent density of which differs from those listed in table.

In determining handling output, it should be borne in mind that shape and storage method of any given material as well as the skill of the crane driver considerably influence the amount of material seized in each operating cycle.

The above diagram shows the tear-off force in relation to air gap between load and magnet. It is assumed that the magnet pole surface is fully covered and that wall thickness of the load amounts to at least one quarter of centre pole diameter. For thinwalled materials, magnetic force is lowered by progressive saturation.

In planning magnetic lifting installations for handling bulk materials such as scrap or pig iron, the guide values listed in the Table can serve as a reliable basis.

All "ELEKTROMAG" Lifting Magnets are of weather proof construction for outdoor use in all weathers. Completely sealed submersible models are available for dipping into waterfilled containers or underwater salvage and similar work.

The watertight cable terminal box has two compartments, each closed off by its own cover. The supply cable is led to the connector chamber(2) through one bolted clamp (1) and is connected to terminals (3) and the earthing screw terminal.

Connector chamber (4) is sealed by cast compound to prevent entry of foreign bodies and moisture into the coil.

Magnets LRH 9 to LRH 19 can on request be fitted with watertight cable terminal box in place of standard plug-in connectors.

Switchgear used for the control of lifting magnets must be provided with adequate protective gear to limit the voltage generated when the inductive exciter circuit is switched off. Provision must also be made for a brief counter flow current surge to de-energise the system and throw off the load.

We supply a wide range of plant and switchgear to feed magnets from 3-phase or DC power mains or generators, in standard and special purpose models to suit all requirements.

To ensure continuity of operation and guard against the danger of accidents in case of power failure, we also supply complete equipments for stand-by or buffer battery operation.

Where the crane driver cannot keep the magnet under visual observation (e.g. special magnets used for raising material under water) electronic instrumentation can be fitted giving optical or accoustic signals to indicate that the load has been seized or released.