US Patent 10230234 Controlled switching devices and method of using the same

This invention describes a method and an electrical circuit for controlling the closing of a three-phase circuit breaker with simultaneous pole operation to mitigate the inrush current resulting from power transformer energization by taking into account the residual magnetic flux in the transformer's magnetic core. It is disclosed a method to perform controlled switching on transformer and therefore mitigate the inrush current. It is disclosed that this method can be applied to any configuration of transformers which can be, but not limited to, Y-Δ, Y-Y, Δ-Δ and Δ-Y with either floating or grounded neutral.