4 research outputs found
Investigating the impact of ferrite magnetic cores on the performance of supercapacitor assisted surge absorber (SCASA) technique
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
Supercapacitor assisted surge absorber (SCASA) technique: selection of magnetic components based on permeance
Supercapacitors help building long time constant
resistor-capacitor circuits. This property helps them withstand
high voltage transient surges and dissipate transient energy
in the resistive element of the circuit without exceeding the
supercapacitor’s DC voltage rating, which is usually between 2.5
to 4 V. SCASA is a patented technique, which was commercialized
within the last five years. Successful implementation of this circuit
topology, despite its simplicity, is quite dependent on the selection
of the core of the coupled inductor utilized. This paper provides
the essential details of the process of selecting the core for
the magnetic component required, with a brief comparison of
SCASA technique with a traditional surge protector, without any
supercapacitors
Optimization of Supercapacitor Assisted Surge Absorber (SCASA) Technique: A New Approach to Improve Surge Endurance Using Air-Gapped Ferrite Cores
SCASA is a patented technique commercialized as a surge protector device (SPD) that adheres to UL-1449 test standards. Apart from the novel use of supercapacitors, SCASA design incorporates a coupled-inductor wound to a specially selected magnetic material of powdered-iron. In this study, we investigate the limitations of the present design under transient operation and elucidate ways to eliminate them with the use of air-gapped ferrite cores. In modelling the operation under 50 Hz AC and transient conditions, a permeance-based approach is used; in addition, non-ideal characteristics of the transformer core are emphasized and discussed with empirical validations. The experimental work was facilitated using a lightning surge simulator coupled with the 230 V AC utility mains; combinational surge-waveforms (6 kV/3 kA) defined by IEEE C62.41 standards were continuously injected into SPD prototypes during destructive testing. Such procedures substantiate the overall surge-endurance capabilities of the different core types under testing. With regard to optimizations, we validated a 95% depletion of a negative-surge effect that would otherwise pass to the load-end, and another 13–16% reduction of the clamping voltage verified the effectiveness of the methods undertaken. In conclusion, SCASA prototypes that utilized air-gapped cores revealed a greater surge endurance with improved load-end characteristics.</jats:p
Magnetic Design Aspects of Coupled-Inductor Topologies for Transient Suppression
Based on the discovery of the surge absorption capability of supercapacitors, a transient protector named supercapacitor-assisted surge absorber (SCASA) was designed and implemented in a commercial device. Despite its simplicity, the circuit topology consisted of a coupled inductor wound around a specially selected magnetic core. This paper elucidates the design aspects of SCASA coupled-inductor topologies with a special focus on the magnetic action of core windings during transient propagation. The non-ideal operation of the SCASA transformer was studied based on a semi-empirical approach with predictions made by using magnetizing and leakage permeances. The toroidal flux distribution through the transformer was also determined for a 6 kV/3 kA combinational surge, and these findings were validated by using a lightning surge simulator. In predicting the possible effects of magnetic saturation, the hysteresis properties of different powdered-iron and ferrite core types were considered to select the optimal design for surge absorption. The test results presented in this research revealed that X-Flux powdered-iron toroid and air-gapped EER ferrite yielded exceptional performance with ∼10% and ∼20% lower load–voltage clamping compared to that of the existing Kool μu design. These prototypes further demonstrated a remarkable surge endurance, withstanding over 250 consecutive transients. This paper also covers details of three-winding design optimizations of SCASA and LTSpice simulations under the IEC 61000/IEEE C62.45 standard transient conditions.</jats:p