Suspended electromagnets work by winding electrically conducting material such as wire or strip on to a high permeability steel circular steel core. When energised, this electromagnet creates magnetic flux leakage which is channelled to return to the core with carbon steel side poles and a backbar at an optimal thickness ratio. This effectively creates a magnetic circuit with a diverging magnetic field, which is ideal for extracting ferrous metal which comes into contact with the magnetic field as they travel along the conveyor belt.
In 2009, Magquip introduced the range of POWERSMART “Self-Air Cooled Belt Magnets” using Anodised Aluminium Strip for the extraction of tramp iron on wide large capacity conveyor belts.
These magnets use “Anodised Aluminium Foil” as the coil conductor winding material. By employing this material, as well as the “direct on to core” disc coil winding method it is possible to have a belt magnet that uses no oil or force cooling mechanism like fans and is naturally self-air cooled with a fully welded enclosure. Anodised aluminium strip is a conductor material with a 5µm thick ceramic oxide (anodised) layer which forms the electrical insulation of the conductor material. No additional covering such as Nomex or glass fire yarn is required.
The efficiency of this type of winding also enables a drastic power consumption savings versus equivalent oil/fan types (Energy Efficient); there is also no difference in magnetic performance comparative to equivalent oil/fan cooled types.
The reduced power consumption is achieved by designing the DC magnet coil winding for as many turns as possible in a certain coil radial depth as opposed to a design with few turns and many amps resulting in similar amp-turns but resulting in more watts loss/ heating which requires cooling oil.
The reduced amperage fed into the self-air-cooled coil means there is less resistive heat loss (Joule Heating) and power consumption (kW). The ANS range of magnets use almost half the kW power consumption of equivalent oil filled magnets for the same magnetic performance. The coil resistive watts loss is not a measure of the magnetic field flux density (gauss). The flux density depends on the diameter of the circular shaped core and the coil ampere-turns. A coil can have a few turns and many amps (high watts), or many turns and few amps (low watts).
The magnets are then naturally cooled by winding the coil directly “on to the core” and letting the core act as a heat sink to conduct the heat to the enclosure. The heat is then radiated out into the atmosphere via the magnet top plate (back bar). This belt magnet cooling in large electromagnets can only be achieved using anodised aluminium strip which allows for a coil winding fill factor of 99%, with a wire wound coil, the air spaces between the wire wouldn’t allow for efficient heat transfer. As the belt magnet coil winding doesn’t require any cooling oil, the equipment is environmentally friendly.
The POWERSMART Self Air-Cooled Belt magnet will extract damaging tramp iron contaminant from trough conveyor belts from 600 mm to 2400 mm and will be effective at magnet operating gaps up to 850 mm.
Typical belt magnet applications are:
- Extraction of tramp iron from conveyor belt to protect belt, mills, screens and crushers.
- Recovery of steel from steelworks slag
- Recovery of ferrous metal in metal reclamation and recycling operations
The MAGQUIP POWERSMART Self Air-Cooled belt magnet have obvious major advantages over oil filled belt magnets and include:
- No coil cooling oil to be topped-up or replaced or disposed of
- No oil spillage or leaks possible, concrete ‘bund’ not required at installation
- 5-year coil guarantee
- Easily certified “Safe for Hazardous Locations” (Flameproof Zone 1 / DIP Zone 21/22)
- Lower “Power Consumption” Watts loss [Total Cost of Ownership]
- Lighter Overall Weight without oil
- Coil takes much longer to reach working temperature, thereby operating at higher amp-turns for a stronger magnet circuit
- Coil power consumption does not have to be reduced for high ambient temperatures like oil filled magnet do
- Disc Winding with anodise foil offers Lower Coil “Inter-turn” Voltages
- Strip offers a Higher Coil winding “fill factor” of >98% vs. Aluminium DGC wire with 66% “fill factor”
- There are no Coil “hotspots” and superior thermal conductivity of resistive heat as opposed to wire windings with oil cooling
Coil & Core:
Anodised Aluminium Strip + S355JR Carbon steel
Coil enclosure:
High permeability S355JR Carbon steel, top and side plates. AISI 304 Stainless steel bottom plate. Lifting and suspension points on each corner.
Pulley support framework:
S355JR Carbon steel Carbon steel parallel flange channels
Pulleys:
Carbine Type from schedule pipe, diamond back rubber lagged with crowning
Pulley guards:
Fabricated carbon steel frame with expanded metal mesh
Cleaning belt:
Synthetic rubber and polyester conveyor belt and AISI 304 Cleaning strips
Bearings:
Drive and tail pulleys square flange type return pulleys plummer block type
Geared motor:
SEW K type Gear Box helical bevel type with Premium Efficiency 4 pole motor TEFC motor
Terminal Box:
Enclosed Carbon steel with cable gland entry and terminal bushings
Power Supply:
Dry type, silicone diode bridge connected transformer rectifier
