Transformer Overloading of Delta Bank Supplying Both 3 ph and ph1 Power

You said...

"(3)the single phase load 115V is shared in the ratio 1/6:5/6:1/6.".

How do you figure that the other two transfortmers contribute anything to your single phase 115V loads? Perhaps I am missing something.

IMHO... your single phase 115V loads will all be provided for by the middle tranasformer and must be connected across the red and yellow phases to the neutral.

Yes, the single phase 115V loads will all be on the center transformer.

You might have an easier time figuring this out if you analyze your loads the way you have broken them up in your 3 points, and then use the principle of superposition to totalize them. Think of it as if you have one transformer bank of 3-50kVA units and a single 25kVA, 115/230V transformer for the 115V loads. The 3-phase 230V loads should be easy to figure. The 115V loads should be pretty straightforward too, and then what's left is to distribute the single-phase 230V loads among the units to balance out as best possible to balance. If the 115V loads are more than 25kVA, then that eats into the kVA available on the middle 50kVA (3-ph) unit for single-phase 230V loads.

Hope I've caught the gist of what you are trying to accomplish.

You could always copy the entire page of your homework question.

"Answers with calculations would be much appreciated." Not from me!

Thank you PeterT and North_of_60 for the suggestions, I upvoted both answers as good. I apologize for typing that TonyS, this is not a homework problem I typed this out as best I could from the description of the problem explained to me by a colleague based on a real world problem. I guess I overlooked the detail with the 115V single phase load being supplied by only the center transformer. I was hoping to get some guidance in the form of a general equation as I am sure this is a common problem and there is no need to reinvent the wheel.

Let me go over how all the loads are distributed with my colleague and I will post them here in point form as best I could.

Now that I think about it, I think we are overlooking a very important detail.

I mentioned that the secondary windings of the three single phase transformers are connected in a center-tapped DELTA configuration. Wouldn't this mean that the currents flowing through the coils of the power transformers be drawn by the center transformer in supplying the single phase 115V load because this is delta? Correct me if I am wrong but that is how I envisioned it.

The current readings are taken from the secondary side of the transformer as illustrated below.

The aim is to find delta phase currents I_RB, I_BW and I_RW using measured line current values I_R, I_W and I_B to determine if these phase currents exceed the rated coil current of the individual single phase transformers (based on rated kVA and secondary phase voltage 230V).