Electropermanent Magnet Eddy Current Separator to Recycle Non-ferrous Metals

This paper proposes and demonstrates the idea of using electropermanent magnet (EPM)-based actuator in the structure of eddy current separator to recycle non-ferrous metals. It uses a coil excited by a full-bridge inverter to statically switch the direction of magnetic flux in the EPM, inducing eddy current within metal particles. This provides a pulsating magnetic actuator to repel non-ferrous metals mixed with other materials on a recycling conveyor. Conventional eddy current separators typically use a costly and bulky rotating permanent magnet drum or a static electromagnetic coil to generate the required repulsive forces. The static EPM-based separator eliminates the need for the expensive rotating drum structure. Furthermore, it reduces power losses compared to static electromagnetic coils by using narrow-band current pulses instead of continuous sinusoidal current. A quadratic approximation of the magnetic flux density is proposed to improve the accuracy of the repulsive force calculation. The paper also elaborates on a core optimization and electromagnetic heating analysis. A proof-of-concept EPM separator is developed and experimentally tested to calculate the repulsive force based on measured deviations in particle angle and distance. Comparing the test results shows an average error of less than 5%, confirming the improved accuracy of the quadratic approximation.