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Libroplantasingl

FUNCTION Induction separators select non-magnetic metals, mainly those in which aluminium is the main component. DESCRIPTION The separation by induction of non-ferrous metals relies on the physical principle behind Foucault or eddy currents. This consists of the creation of an alternating magnetic field, that is, a variable magnetic field in which the north and south pole alternate. This variable magnetic field is created in the unit by an induction drum mainly made up of neodymium rare earths and a rotation speed greater than 3,000 rpm. In this way if a non-ferrous material is subjected to an alternating magnetic field, internal currents known as eddy currents are generated. These currents generate a magnetic field opposite to the variable magnetic field generated by the magnet. This strong opposition of magnetic fields causes a repulsive force such that the non-ferrous material is displaced from its normal trajectory and thereby separated from the stream of the other materials. In addition, the drum also induces secondary electromagnetic currents that attract ferromagnetic metals towards the drum. These currents can be used to separate the ferrous material fed into the unit. An induction separator comprises two rollers: the drive roller that moves the unit belt through a gear reducer, and the head roller or induction drum, which generates the eddy currents. The induction drum is formed in turn by two drums, an outer one revolving at the same speed as the conveyor belt and an inner drum that generates the eddy currents. Therefore, as shown in the figure on page 121, the stream of material fed into the induction separator is divided into three currents: • Non-ferrous metals • Ferrous metals • Other materials Induction separators


Libroplantasingl
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