Phase shift transformers 1

[electrolitic]

What does it mean exactly and in details:
Vector Group Dd11.75 d0.75 and
Dd0.25d11.25.
Thanks

 

[DTR2011]

Your question is a bit vague, but a PST does just that. It is used for power flow control. SEL has a nice application paper explaining the nuts and bolts of the design and operation.

 

[electrolitic]

Sorry
These transformers (double secondary each) feed VFDs and provide harmonic mitigation.
The first one gets +7.5º and the second -7.5º.
This means 24 pulses for harmonic cancellation, I suppose.
I would like to know the meaning of numbering 11.75, 0.75, 0.25...
Thanks again

 

[Masbibe]

electrolitic,

11.75 means 11h 45 minutes
0.25 means 12h 15 minutes
0.75 means 12h 45 minutes

on phasor diagram representig as clock (12h is zero degree)

Milovan Milosevic