Mn-Zn Ferrite Round Cable EMI Suppressor With Deep Grooves and a Secondary Short Circuit for Different Frequency Ranges

A novel Mn-Zn ferrite round cable electromagnetic interference (EMI) suppressor with deep grooves and a secondary short circuit was constructed, realized and measured. Three steps were passed in novel suppressor development: from developing a suitable magnetic material, to constructing a suppressor device, to forming a new class of possible applications. Soft ferrite feedstock was formed from fine commercial Mn-Zn powder and a Solvent system binder based mainly on wax. Cylinder-shape cores with grooves were injected by powder injection molding (PIM) technology, chemically and thermally debinded and sintered at optimal conditions (1280°C/2 h). The samples were aimed to serve as cores for EMI suppressors on cables. Their impedance versus frequency was measured using the core length as a parameter. After that, copper wire was placed into the grooves on the outside surface of cores to form a secondary coil and different configurations were considered. The contribution of the short circuit coil inserted into the grooves to EMI suppression was measured and analyzed also. Maximal impedance values can be achieved with a secondary short circuited winding which passes through every groove. It was also shown that ferrite cores of the same length could be used for different frequency ranges by changing the configuration of secondary short circuited windings.