Investigating the impact of ferrite magnetic cores on the performance of supercapacitor assisted surge absorber (SCASA) technique

Abstract

Supercapacitor assisted surge absorber (SCASA) is a patented technique developed by the University of Waikato. One noticeable attribute of this design is the inclusion of a coupledinductor which improves its capability of surge absorption. This paper mainly focuses on investigating the usability of ferrite iron for the core of the coupled-inductor, and attempts to explain how to minimize the effects of a negative voltage peak that arise during SCASA operation. Four ferrite cores with different geometries and material compositions (W-ferrite and J-ferrite) are subjected to 6.6 kV surge hits. Experimental outcomes demanded the need of inserting air-gaps inside these ferrite toroids. High magnetic permeability of ferrite results in a low energy storage capability; this limits their suitability in surge absorption related applications. To overcome the issues of high permeability we modified the cores with thin cuts through the surfaces. Experimental work is facilitated by lightning surge simulators (LSS-6110 and LSS-6230) coupled with the utility main to generate surge waveforms defined by the IEEE C62.41. The analysis of test results encourages us to justify the gappedcore approach, and to further verify, performance of SCASA is empirically compared for both powdered-iron cores and modified ferrite cores using international protocols of UL-1449.