Three-phase transformers are used to convert the available 3-phase mains voltage into any load voltage. To cater for the wide range of application areas involved,these transformers are essentially available in the same kinds of designs as the single-phase transformers, e.g. Three-phase dry-type transformer: separate winding version Three-phase series transformer: autotransformer winding version Three-phase safety, isolating, mains or insulating transformer: separate winding version In terms of how the 3 coils are connected, there are various options available and each of these provides the transformers with specific properties. The vector group code is composed of the following elements: The upper-case letter indicates the higher-voltage winding (the highest voltage in terms of operation). The lower-case letter indicates the lower-voltage winding. The brought-out neutral is indicated by means of N or n (depending on voltage level). â?¢ The distinctive number indicates the phase angle of the lower voltage in relation to the higher voltage (distinctive number multiplied by 30). The following winding connection options are available Delta: D, d Wye (or star): Y, y Zigzag: Z, z Example: Dyn5 Higher-voltage winding is delta-connected. Lower-voltage winding is star-connected with a brought-out neutral. The lower voltage lags behind the higher voltage by 150�° (5 x 30�°). Unless specifically requested otherwise, the transformers are configured with a double-star connection and a brought-out neutral (vector group Yyn0); for autotransformers the vector group is YNa0. Our three-phase transformer range includes all our standardised types for the 25 30.0 kVA performance range and a frequency of 50/60 Hz