With its real 3-phase test circuit, the PATTR-3D can address complex ratio measurements of Phase- Shifting/Regulating or irregular vector group type transformers, otherwise impossible to achieve with conventional ratio meters. Zigzag type transformer testing is very easy and will not require the installation of jumpers or the use of relay matrix circuits. The single or real 3-phase voltage output up to 275 V contributes to higher magnetisation currents and therefore stronger flux for better signal reflection on secondary and/or tertiary windings allowing more accurate results. The PATTR-3D phase displacement measurements enables for simple detection of the transformer vector group.