Transformers with „V” connection

The transformers with windings in Vv configuration can reduce a disadvantageous asymmetry occurring when 1-phase receiver is supplied from 3-phase network.

Special transformer of ET3V1 type
The problem of maintenance the load symmetry appears in particular when high-power 1-phase receiver is to be supplied from a 3-phase network.
Traditional supply of such receivers with phase-to-phase voltage of 3-phase network causes a strong asymmetry in the electric network, loading only two phases.
As it results from Fig. 1 when ET3V1-type transformer is applied, then all three phases of the supply network are loaded. In presented solution the asymmetry of load also occurs, but it is considerably smaller than during supply of 1-phase receiver directly from network. Besides in respect of receiver operation safety it is also advantageous to separate the transformer circuits galvanically.

Fig.1 Increase of load symmetry due to the application of ET3V1-type transformer

Correct overload and short-circuit protection of Vv transformer on the primary side can cause some problems due to twice higher current in the middle phase. In such situation it is necessary to make short-circuit calculations taking into consideration the specificity of transformer construction and then select the fuse-elements individually for each phase.

Fig.2 Configuration of windings connections for ET3V1-type transformer

It is difficult to classify explicitly the transformers with Vv winding as 1-phase or 3-phase transformers. Such a transformer is supplied with voltage from 3-phase network, but it is loaded with 1-phase receiver. This transformer has been designed by modification of Dy connection group. Primary and secondary windings have been removed from central column of the transformer. Other two extreme coils are linked in Vv configuration presented on Fig. 2.
The basic advantage of such transformer is a significant reduction of load asymmetry, which decides on its application in technically difficult situations, e.g. for supply of 1-phase uninterruptible power supplies (UPS) from 3-phase network.
Specific construction affects the working parameters of the machine.

ELHAND transformer of ET3V1-type