... of three - phase windings BBC transformation ratio group tester for transformerthe tester for transformer is a newly developed kind of transformation ratio auto ... measurement of transformation ratio, group (polarity), error of groups of transformer in model of Δ/Y,Y/Δ,Y/Y,Δ/Δ,Y/Z,Z ... 0.5%Measuring range of group 00~11(00 standards for 12)Working conditionInput voltage AC 220±22V 50Hz±1Hz Temperature ...