Sumitomo Electric Industries Ltd of Itami, Japan, has developed an improved process for the manufacture of a pure iron-based soft magnetic composite (SMC) powder core for automotive reactors thereby achieving a 10% downsizing and weight reduction compared with a conventional reactor produced from electromagnetic steel sheet.
The company states in a report published in SEI Technical Review (Naoto Igarashi, et al, No.80, 2015, pp 98-103) that the SMC pure iron powder reactor cores are used for boost converters which convert (boost) the voltage in automotive motor drive systems in hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs) (Fig. 1).
The reactor boosts the voltage by alternatively accumulating and releasing magnetic energy, and it also smooths the ripple current that is generated in the boosting process. The pure iron SMC powder core is said to be the key component to achieve the reactor’s function.
The reactor cores, which consist of two side cores (essentially semi-cylindrical shape) and six middle cores (box shaped parts), are produced by compacting iron powder whose particles are insulation coated to increase the electrical resistance of the component.
SEI states excellent AC magnetic properties are achieved in the high frequency range (1 kHz or higher) and that due to their three-dimensionally isotropic magnetic properties, SMC core materials are expected to find applications where the required shape of the component would be difficult to achieve using conventional electromagnetic steel sheet, but could be achieved by powder compacting.
SEI also reports that in optimising the iron powder particle size (Fig. 2), and developing a compacting process which avoided damaging the insulating layer on the iron powder, it was able to produce SMC cores which take full advantage of the pure iron material’s high magnetic flux density and at the same time offer the end user reduced weight.