A Non-Control Transformer Inrush Current Limiter

A new method is proposed for inrush current reduction of under load transformers. The proposed limiter consists of a control-less diode-bridge and a single coil that connects in series with each-phase of transformer. It is necessary using three similar circuits for three-phase transformers. The limiter has almost no effect in normal operation of transformer. The simplicity of proposed circuit, easy to build and absence of control circuits are the main attractive points of circuit. The equivalent instantaneous inductance of transformer is used for instantaneous analysis of circuit operation. The analytical analysis and designing characteristics for DC reactor inrush current limiter are presented. The overall circuit operation in transient and steady state cases are studied in detail. The paper is focused on reduction of inrush current of under-load transformers. Simulation results are obtained using PSCAD/EMTDC software to verify the valuable operation of proposed circuit in reduction of inrush current. The results are used for comparison of inrush current with and without using the limiter.