Importance of Leakage Magnetic Field and Fringing Flux in Surge Protector Design

Abstract

Transient surge absorption capability of supercapacitors is practically implemented in a commercial surge protector known as supercapacitor assisted surge absorber (SCASA). It is a low component count high performance circuit design which utilizes a coupled inductor topology wound to a powdered-iron magnetic core. This paper investigates non-ideal characteristics of the SCASA transformer designed using various air-gapped ferrites such as manually gapped toroids and mass-produced commercially available EER cores. Emphasis is given to examine surge energy losses associated with leakage magnetic field and fringing flux of gapped transformer prototypes. In predicting effects of an air gap in ferrite materials, an analytical approach based on effective-permeance is used with validations based on SCASA inductance properties. Experimental work presented in this paper are carried out using a Noiseken lightning surge simulator adhering to IEC 60038 and IEEE C62.41 standards. In addition, SCASA prototypes were subjected to surge immunity tests specified by UL-1449 Underwriters' laboratory procedures, where a 10% reduction of load-voltage was recorded outperforming the present design.