Transformer Problem

Have you any idea of what you're talking about?

You want a neutral out of a star-delta transformer?

I cant blame you for your comment but my intention really is to seek experts opinion on the requirement of a customer. On why they require a balance 460/sqrt of 3 line to ground is one thing that had not been cleared sufficiently to me in our discussion.

From what I have gathered it is a requirement of the relays of their water purification facilities to monitor this balance line to ground condition and for that purpose only.

Why do some customers talk complete boll codswallop <rhetorical question>?

So you have a "wild-leg delta" configuration on the secondary now (giving you two 230V single-phase connections and the unusable 400V from the opposite phase to ground)? And you would like to take the 460V, 3-phase and feed it into a 460V wye - 230V delta transformer to get a true 230V, 3-phase system for those loads? You should be able to do it. If you are taking all the 230V load off the wild legs and moving it to the new transformer's 230V secondary, you could eliminate that ground connection and then you will be just fine. It probably would still work if you left the ground, but unless you have any single-phase loads there that you can't transfer, you shouldn't need it.

I guess I understood his intent differently (although he didn't quite say it this way)--I thought he intended to lift the existing ground at the midpoint of the one leg of the delta and create a new ground for the 460 volt level at the neutral of the wye primary of the new 460V wye - 230V. In concept, I think that can work.

There are probably other factors to consider, including the rating of that new transformer, such that it can carry an appropriate level of ground current (and / or appropriate protective relaying).

If what I described his his intent, another alternative would be a zig-zag transformer, but that could not be used to supply their 230 volt loads.

Yes you are correct that it was the way im thinking.

thank you

You (or somebody) need to list all the loads by both voltage and number of phases, in order to determine what will be cost-effective.

If there needs to be another transformer, it would be delta-star, not star-delta.

thank you

As the other guys said, by creating a neutral for the low voltage winding won't do any good. Instead a delta-z connection is a connection that self balances, not much but enough when using slightly umbalanced loads (20-30%). Second option, try to balance the loads by using balancing schemes if necessary. the kind of schemes used for arc furnaces maybe, the situation being similar.

thank you