Demagnetization Method for Reducing Inrush Current of Single Phase 1 kVA Transformer

I Made Yulistya Negara, Dicky Wahyu Darmawan, Ryan Nurdianto, Dedet Candra Riawan, Arif Musthofa, Dimas Anton Asfani, Mochammad Wahyudi, Daniar Fahmi


This study deals with an effort to reduce inrush current of single phase transformer during its energizing. Inrush current affected by residual flux was minimized using demagnetization method in order to reduce residual flux trapped in the core of transformer. Two methods of demagnetization namely variable frequency-constant voltage (VFCV) and variable voltage–constant frequency (VVCF) were applied and the effectiveness of both methods were then compared. Both methods were supplied with alternated direct current (DC), however the one was changed its frequency and the other one was changed its voltage. The results obtained after transformer was demagnetized using these methods show that VFCV method educed inrush current up to 76%, on the other hand VVCF ethod reduced inrush current only up to 37%. Moreover, demagnetization time process of VFCV method was about 1.46 s, which is 1 s faster than VVCF method.

Keywords: demagnetization; inrush current; variable voltage-constant frequency; variable frequency-constant voltage

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