Disc wound

Disc wound anodised aluminium
strip coil and core assembly

Tramp iron if undetected, can wreck millions of rands worth of belts and processing equipment before being detected.

That is why electromagnets, suspended over conveyor belts, are essential to any bulk materials handling system. By removing tramp iron, they prevent immensely costly damage and downtime.

An electromagnet basically is an electric coil wrapped around a steel core inside a steel enclosure. The electrical power consumed by the coil is converted to heat. To limit the coil temperature, the heat from the coil flows to the enclosure and is radiated into the atmosphere. Two cooling options can be employed.

With natural oil cooling, the coil heat is transferred to the transformer oil contained in the enclosure. With natural air cooling, with a special coil construction and winding method, the heat from the coil is transferred to the core and then the enclosure.

Traditionally, the electric coils are wound with aluminium wire covered with fibre glass yarns. The wire weight in an oil-cooled magnet is substantially less than that in an equivalent performance air-cooled magnet. Adding the additional cost of the oil, the material cost for an oilcooled magnet is 10 to 20% less than that of an air-cooled magnet.

However if the coil of an air-cooled magnet is wound with anodised aluminium strip, the coil weight and enclosure height is reduced and the material cost compares to that of an oil-cooled magnet. In addition, these magnets weigh less and consume half the electric power of equivalent performance oil-cooled magnets with covered aluminium wire coils.

The installation cost is less as is the operating cost. The weekly inspection of the oil level and the three monthly removal and replacement of the moisture drain plug is not required.

Anodised aluminium strip has several advantages for electromagnet coil windings. The anodised film can withstand a temperature of 2,000C, and will not burn out. The film is only a few microns thick, and the coil fill factor is 99%, compared with 65% for covered wire coils. With no air space between the conductors, heat transfer through the winding is enhanced.

Strip coils are disc wound, although the volts per layer are the same as the volts per turn.

A complete range of air-cooled electromagnets with anodised aluminium strip coils – both manual cleaning and self-cleaning types – for belt widths from 600 mm to 2400 mm, is available from Magquip.

Tel: 011 473 2521
Fax: 011 474 3633
E-mail: info@magquip.co.za