Three-phase vector group (Dyn11, Yd…)
The star/delta connection of the windings and the clock index.
Definition
The vector group of a three-phase transformer describes how its three primary and secondary windings are interconnected: in star (Y), in delta (D), or in zigzag (Z). The notation combines the primary coupling (uppercase) and the secondary (lowercase), followed by a number: for example Dyn11.
This number is the clock index: it indicates the phase shift between the primary and secondary voltages, expressed in multiples of 30° (like the hours of a clock). The vector group determines the presence of a neutral, the behaviour towards harmonics and imbalance, and the ability to parallel transformers.
The Dyn11 group, very common in distribution, offers a neutral on the secondary and good behaviour towards unbalanced loads.
The ABL tip
The choice of vector group depends on your need for a neutral, your type of loads and any paralleling. Describe your installation: we recommend the best-suited group and clock index.
