Dy11 and Dd0 transformers

[144x]

in an industrial plant there is a 6 KV 50 HZ busbar that some DC motor are connected to it via AC/DC converetr .every other motor are fed by a Dy11 or Dd0 transformer(I mean Dy11 Dd0 Dy11 Dd0 etc.)all the motors are similar. is there any explanation for this arrangement ?is there any web site to obtain some information
thanx.

 

[busbar]

It's possible that other transformers are paired for 12-pulse conversion, but the odd one only a 6-pulse design. That would produce a higher ripple-voltage DC output and more lower-order harmonics {not as easy to filter/needing larger/more inductors and capacitors} compared to 12-pulse assemblies.

 

[jbartos]

Suggestion: Visit

http://www.sea.siemens.com/step/pdfs/dcd_3.pdf

http://www.bucyrus.com/ACTech_CIM2001.pdf

etc. for more info