A Saturated Amorphous Alloy Core-Based Inrush Current Limiter to Eliminate Inrush Currents and Restrain Harmonics during Transformer Energization

Abstract

In this paper, a new saturated amorphous alloy core-based inrush current limiter (ICL) has been designed and built to limit the inrush current of a power transformer. A toroidal core with a middle limb is developed using the Metglas amorphous alloy and the middle limb is excited with a dc current to saturate the amorphous alloy core. Only a very small dc excitation current is required using such a core when compared to that using a similar design with conventional materials. Under normal conditions, the saturated amorphous alloy ICL core steady-state impedance is low and has a negligible effect on the operation of the system. During the energization of a power transformer connected to the ICL, the large inrush current de-saturates the amorphous alloy core, resulting in an increase in the ac winding impedance, which limits the peak amplitude of the transformer inrush current and harmonics. To validate the proposed saturated amorphous alloy core-based ICL, a prototype ICL has been built and tested in the laboratory. The experimental results show that the core power loss, core saturation, the fundamental and harmonics of the inrush current of the proposed saturated amorphous alloy core-based ICL are significantly better compared with those from the sheet steel core-based ICL. It is expected that the proposed saturated amorphous alloy core will be used in future inrush current limiters that can help to improve the performance of the power transmission and distribution system.