Two 2ry delta feeding a converter 1

[marbr2005]

Instead of a conventional back to back 6 pulses converter connected to a single secondary winding I found an old circuit where each set of thyristors is connected to a separated delta winding.Reactors were introduced between the DC buses of the two thy groups.I would like to understand the reason.Thank you.

 

[davidbeach]

Not much to be gained from two six-pulse converters connected back-to-back from the same source. Connect each to different sources with a 30 degree phase shift between sources and you have a 12-pulse converter. The inductor is used to aid in the commutation. Are you sure both transformers have delta secondaries? If so, it is highly likely that one has a delta primary and the other has a wye primary.

 

[marbr2005]

Thanks
I am really sure that transformer is a delta/delta/delta.This converter is used to drive a shear (left side) that must be electrically synchronized with right side shear.
How much to be gained from two six-pulses converters connected from the same source?

 

[itsmoked]

None other than the ability to run a larger load than individually. If one can handle the load then there is probably no advantage.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[davidbeach]

Somehow, when I first read it, I had the impression of the two sets in series. If the two converters are in parallel, that allows the load to be greater than the capability of one converter. The inductor is to balance the load sharing between the two converters.

 

[marbr2005]

Sorry. Surely the misunderstanding is caused by my bad english. One 2ry winding feeds the forward bridge. The other 2ry winding feeds the reverse bridge.
The question is the gain if compared with conventional arrangement back to back fed by a single 2ry winding.

 

[davidbeach]

Another possibility, now that you mention forward and reverse, is that the converters operate in opposite directions to allow four quadrant operation; power in for both directions of rotation and power out (regenerative braking) for both directions of rotation. Not sure how/where the inductor might be connected.

 

[marbr2005]

Mr.David
The motor runs just in one direction but I think you are right.
I will try to "draw" it.
At left side consider fwd bridge fed by the first delta 2ry.Positive bus at top.Add a reactor and HSCB and create node A. At right side consider the reverse bridge fed by the second delta 2ry. Positive bus at bottom. Add a HSCB and reactor and create node B.Complete fwd negative bus to B and rev negative bus to A. Motor is connected at A an B.I think that this configuration can provide motor plugging in order to achieve better synchronization with the other blade drive.( It is a plate mill shearing line)
Am I right?
In such a case, is this configuration better than conventional back to back?

 

[davidbeach]

Sounds like a four quadrant drive. Beyond that it is going to rapidly go beyond what I'm familiar with.

 

[marbr2005]

Hi Mr.electricuwe
You was MVP solving my doubt about 12 pulses series converters some months ago.
Could you please help me again?