To coat fibre optics cables a direct current voltage of 14,5 kVDC and a current of 2 A should be available. The rest ripples should be as small as possible and the transformer voltage stiff.
By using the vector group Dd0y5 a 12 pulse rectification can generate a stable DC voltage. With a good linking between primary and secondary we can reach a small short circuit voltage. For a voltage regulation the primary winding gets 5 tappings.