An improved method for the inrush current evaluation in single phase power transformers

The paper presents an automatic procedure for quantitative evaluation of energizing inrush current of a specific range of single phase power transformers: 1.2-25 kVA. Starting from transformer main rated data and core magnetic H-B characterization, the first peak value of inrush current is accurately estimated. Additionally, the harmonic content of its waveform is also investigated offering valuable indicators of this transient phenomenon. The predetermination of the main inrush current characteristics becomes very useful in avoiding its countless undesirable effects on both the transformer and the installation where the device operates. The proposed method offers a fast and flexible solution of the energizing inrush current problem for the main general purpose single phase transformers.