This final report discusses about controlling configuration variations of coil connection on 3-phases transformer. This paper aims to make the variation of coil connection on 3-phases transformer. This tool can change the 4 coil connection on a transformer, they are wye-wye, wye-delta, delta-wye, delta-delta by utilizing the push button 4 and 6 pieces relay controlled by ATMEGA 8535. This tool …