Inrush Current Limiting of Transformer Primary Winding With Grounded or Nongrounded Y-Connection Using Diode Bridges

This paper presents two novel limiters for mitigating inrush current on primary grounded and nongrounded transformers. The simplicity of structure, reliability of operation with a low failure rate, and a lack of influence on steady-state operation of transformers are some benefits of the two proposed inrush current limiters (ICLs). In addition, they do not require any data for the switching angle of circuit breakers or measurement of residual flux. Additionally, the number of diodes and the inductance value of two proposed diode bridges decreases compared to a three diode bridge in three-phase structures and improve bridge type inrush current limiting for primary grounded and nongrounded transformers. The two proposed methods for inrush current limitation are applicable for all transformers, which have a Y of Yn connection in their primary side. The proposed methods can be used for Y-yn, Yn-yn, Y-delta, Yn-delta, and Y-zn connections and there is no limitation on the secondary side winding type. To reduce losses in the steady-state condition, the ICL should be bypassed. To bypass the ICL, at least three switches are used for the topology proposed in conventional methods. For the topology presented in this paper, only one switch is needed to perform the same function.