Electronic – Y/Y/Δ or Δ/Y/Δ transformer for a series connected 12-pulse rectifier

powerrectifiertransformertransmission

I'm aware that 30° shift is needed in order to obtain a 12-pulse rectification, however, I'm a bit confused about the configuration of these transformer. In most HVDC systems that appear in Alstom – HVDC for Beginners and Beyond, for example, shows a WYE winding as primary:

enter image description here

However, I stumbled upon this similar ResearchGate question but it was answered as the Y/Y/Δ configuration is used and that's why I got confused.

I'm doing a simulation on PLECS in stationary state of this series connected 12-pulse rectifier so as long as I can represent leakage inductances and 30° shift it's okay as I won't do neither a transient analysis nor a fault scenario. However, I want to clarify this to at least justify why I used one configuration or the other.

Best Answer

A 3 winding power transformer isn't equal to a 12 pulse conver transformer. A 12 pulse transformer can have 4 windings. 2 HV and 2 LV windings. The HV and LV windings are arranged in double tier for better decoupling (still a coupling exsiting) of the winding systems and to have equal short circuit voltages.