Sorry about the comment on the "Break the delta". The effect is very evident on the secondary of a four wire wye:delta. Breaking a primary delta will defeat the purpose.
I have always considered "Circulating currents" to be unwanted and possibly destructive currents, whether in a delta winding, core laminations, bus bars or whatever.
A circulating current, just like a load current, has a corresponding current in the companion winding.
Circulating currents that I have encountered and corrected are I believe, zero sequence currents, in that the problem current has the same phase angle in all three phase windings of the delta, both primary and secondary.
This circulating current will combine vectorily to the load current in the windings. The resultant current may be much greater than the expected load current in at least one phase and often less than the load current in the other phases.
A delta wye transformer bank is basically three independent single phase transformers. Connect a single phase transformer line to line on a three phase supply and the load current will still be accurately reflected in the primary winding, just as if the transformer were connected to a single phase supply. Other loads on the three phase system will not affect the currents in the transformer windings and the ratio between primary and secondary will still be accurate.
Anyone who has worked with the larger single phase generators that have been converted from three phase to single phase will be familiar with the current split when a single phase load is applied to a delta transformer winding or a delta connected generator stator. The connection does not create circulating currents at the fundamental frequency.
We may have a misunderstanding concerning terms.
Three phase transformers with three legged cores may have issues with circulating currents caused by the phantom delta but three single phase transformers with a delta primary and a wye secondary have no mechanism to create circulating currents in the delta primary, even if they are different impedances.
And the real, destructive, transformer destroying circulating currents that I have encountered do not cancel. Often line conditions on one phase will cause the current and determine the phase angle of the circulating current. The total current in each phase will be the vector sum of the circulating current and the load and exciting currents. I have seen the circulating current exceed rated full load current of a transformer.
But you don't get that type of current with a delta primary and a wye secondary on a three transformer bank.
Bill
--------------------
"Why not the best?"
Jimmy Carter