Current Inrush Mitigation Method in Transformers Without an External Power Source or Complex Circuitry

Abstract

David Meisel

Coil based devices such as transformers are rated for maximum continuous current operation. However, during the first few A.C. cycles at power up, input current (otherwise known as inrush current) can exceed ten times the rated continuous current of a transformer primary winding even with the secondary winding unconnected. These extra high inrush currents can cause nuisance circuit breaker tripping, winding insulation degradation and make black starting difficult. This is especially important when high efficiency transformers are used, as they tend to have higher inrush currents. The proposed circuit is a “fundamental” transformer design addition with respect to power up characteristics.

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