Voltage compensation-type inrush current limiter for reducing power transformer inrush current

When a transformer is initially energised, its iron core is driven into saturation, which will result in high-amplitude magnetising inrush current. For lessening this transient phenomenon, a voltage compensation-type inrush current limiter (VCT-ICL) is presented in this study. The VCT-ICL can automatically insert high impedance to restrain the sudden change in line current. After completing the restriction of inrush current, the VCT-ICL freewheels, and acts as a short circuit. Thus, other than performing the restriction, the VCT-ICL has a negligible effect in the circuit and the transformer seems to connect directly with the voltage source. When a load is connected at the secondary side of the transformer, to adjust the magnitude of DC reactor current so that it is equal to or higher than the peak of line current, there is almost no distortion to the load voltage and current waveforms during the steady state. A 5 kVA single-phase power transformer is used as an example to demonstrate the performance of the proposed limiter. According to the simulated and experimental results, the feasibility of the VCT-ICL has been verified. Moreover, increasing the insulation levels of the related components in the proposed limiter allows it to be applied in high-voltage distribution transformers.