Convertor Transformer (Dual Secondary)

they are phase shifted to reduce harmonics

DznDyn11 ? please show connection diagram for this vector group . .

Such 3 winding transformers are used in arc furnace loads, are wherever power electronics loads are used. The key is to have 30 degrees phase shift between secondary windings.

In my opinion DZn actually stands for Delta with zig-zag transformer grounding and provides a ground return path just like Yn.

the secondary Yn has a 30 degree phase shift with respect to secondary delta or with respect to primary Delta. It is likely there is no phase shift between primary Delta and secondary DeltaZ.

Such schemes are used for 12 pulse inverter/converters to reduce the harmonics.

. . i know zig zag windings . . . but never seen anything called "Dzn" . . . i think there is some typo in that question . . .

zig zag trafo is used to ground delta side and hence the OP must have used DZn.This is actually 2 transformers one D/D and on D side Zn is connected and OP must have combined D and Zn of secondary side as DZn.

Dzn0yn11(one is zig-zag winding & another is star having both secondary neutral grounded)

GA