Delta transformer feeder current calculation

[Do You Like Ham]

Similar to my post on Friday, I have a question about what I think is a questionable result in an App.

Scenario is this: a 240V mid tap transformer secondary has a mix of loads on it, for simplicity sake, let's just say there are 3kVA on one of the 120V legs, and 4kVA on the other.

This is a link to an image... (sorry, seems that the new update to the forum has made it not possible to upload images??)

https://ibb.co/qnFz1R1

The transformer primary could be Delta or Wye... in both cases, the end result is that the load is carried over to the associated line, such that
Line A reports that it has 3kVA
Line B reports that it has 4kVA

And, in both cases, it is computing the current by dividing by 277, resulting in
10.83A on A
14.44A on B

For the Wye case, this seems correct.. is it?

For the Delta case, there is one circuit, wouldn't both conductors have the same current? (7000VA/480V = 14.58A)?
(I think the answer to this is yes... same case as https://forums.mikeholt.com/forum/a...ent-on-primary-side-of-center-tap-transformer - the transformer doesn't care if it is a single transformer, or one of three transformers in a 3-phase transformer... correct?)

 

[synchro]

In your schematics are you trying to depict a separate single-phase transformer attached to the output of a delta or wye 3-phase transformer? Or are you wanting to show a part of the delta or wye transformer itself. That makes a difference.
In a delta transformer, the output current on each line is the (vector) sum of the current from the two windings (aka phases) that are connected to that output. So the output current is not the current in one winding. That being said, if a load is attached to 2 line outputs of a delta then the RMS current will be the same in each wire to the load.

Your schematic for the wye has issues because the left side if the transformer has A and B phases with a neutral return connection, and so these are 120 degrees apart (which is consistent with the 480V L-L and 277V L-N voltages shown). The right side of the xfmr shows a center-tapped single phase winding with its corresponding voltages. These are incompatible on the same leg of a transformer core.
If you disconnected the neutral, the schematic could represent a single-phase transformer attached to two line outputs of a wye, but it could also just as well be connected to a delta with 480V L-L outputs.

I suggest you get and use a Spice circuit simulator in AC circuit analysis mode to test your schematics and your simulator results. LT-Spice is one of the free versions