The invention relates to an electric device, especially to an output of a transformer, said output comprises a connecting portion, said connecting portion comprises a connecting rod, which partly inserts into said connecting portion and has an interference fit with said connecting portion, said connecting rod comprises a conductive first column portion that has an interference fit with a busbar, said first column portion axially arranges a conductive second column portion which has an interference fit with said first column portion, said second column portion is located inside of said first column portion, a thermal expansion coefficient of said second column portion is greater than that of said first column portion. Said transformer has such advantageous effects, 1. the same overlapping length increases more conductive surface for reducing a current density to achieve low temperature rising of connecting part; 2. amount of material is reduced and save the social source; 3. the electric clearance or safety distance is increased, an electric safety of device is also increased; 4. a width of a connecting part is reduced, an occupation space of transformer is also reduced.