First online complex Delta-Star or Delta-Y Transformation Calculator is ready

I am curious about this post.

1. Was it a homework assignment?
2. Are there many people who would find it useful?
3. Is it not easier to derive the formula yourself than to remember where it is in your files and how to use it?
4. Would a simple spreadsheet not do it?
5. Certainly Maple or Mathematica would find the comples transformation a snap.

1)hopefully not for someone taking circuit theory where 3) is more useful 2)not really -it is one of the network theorems that is sometimes useful 3)absolutely true. 4)sure 5)yes- J or APL also work well

But- it is pretty!

Textbook/handbook stuff. Nothing new here. Sincerely,

Hello, and I probably overreacted a bit. What is new I guess is the convenience of an online calculator. My apologies to the ng and the OP. Sincerely,

However- how often have you needed such a calculator? Also, if so, how often would you either look it up or work it out from scratch as I have often done simply because I either forgot or was too lazy to look it up? It is not a teaching tool.

I have dealt with a lot of circuit analysis over the last 60 years but over this time, my use of star delta transformations has declined considerably as (a)I am looking for complete circuit solutions (b)If I am trying to reduce a circuit to a thevenin model--why bother when there are more powerful methods such as Z-bus which take advantage of the computer. (c) In relatively few cases I want to use this for its own sake.

Admittedly this calculator may be useful as part of a set of tools

-provided that set was all in one place and results could be saved and applied elsewhere. To some extent a language such as APL or J then allows considerable freedom along with the use of pre-defined transformations such as the delta-wye. As an aside, in J, the delta-wye transform and the y-delta transform each take one short relatively readable line. As with Patrick, I am sure that I learned more about programming than about the theory.

I agree fully with Don. It is more trouble to keep track of such a tool than it is to look it up or derive. When you do get to the tool, you also have to figure out how to use it. In my case, my reason for using the transformation was mostly to study the transformation's properties than a need for the transformation itself. It has some interesting attributes.

For example, use upper case letters to label the delta resistors (or impedances). Use lower case letters for the Y such that A and a do not touch, etc. Then A, B, C, a, b, c form three balanced bridges.

A*a = B*b = C*c = A*B*C/(A+B+C) = a*b + b*c + c*a.

Thus, once you do one of the two calculations on the right, you have the cross multiplication product that balances the bridges.

This is interesting -you have hit a core of the problem. Going from A (Z12) B (Z23c) C (Z31) to a b c or z1n z2bn z3n works nicely -i.e going delta to wye. However there may be a problem going the other way- to deal with this one must say Z12 =A =(z1n*z2n +z1n*z3n+z2n*z3n)/ z3n or (ab+ac+bc)/c The problem is that the numbers are right but as you have indicated A and a do not touch. There is a rotation which is a problem of nomenclature - what is fixed is the terminals 1, 2,3 and we are dealing with Z12 etc or z1n etc (n being a 4th or neutral terminal not present in the delta).

I have seen transformations, in Wikipedia for example, where the nomenclature is not symmetrical. That is why I would have used A=Z23. B=Z31 and C=Z12. Because each resistor in the delta will have one and only one resistor in the wye which is not touching it, the pairs of such resistors are Aa, Bb, and Cc. If you know one of these products you know them all. Knowing either the delta or the wye values give a nice symmetrical equation for this product.

To my mind, the transformation was used to break a network down to series and parallel connections that are easy to calculate. I almost never did that. I used mesh currents to get a set of simultaneous equations. Before that, the Kirchhoff laws were the way to go. With modern computers, there is hardly any reason to use the transformation. The only benefit I can think of is that comparison of the delta and wye equivalents gives some insight into a particular combination.

It could be that I am missing the entire point.

You are right- One does need double subscripts to deal with this properly. You know what is going on and the format and have put the clue in considering the "one and only resistor in the wye that is not touching" You use, properly a double subscript notation. Dealing with an idiot box, inputis of the form a b c where awhat is referred to may be Zab,Zbc, Zca or in the reverse case Zan,Zbn, Zcn. Check it out regarding the preservation of the terminals A B C.

As to the need for the transformation- I agree- use Kirchoff. From my viewpoint as it appears is yours, use of I =YV (mesh) is better than V-ZI (loop) simply because in most cases it results in fewer simultaneous equations and is generally better for computer modelling because once a choice of reference bus is made (in power systems it is easy), the rest can be automated. It is messier with loop methods as there are so many choices.

What I see too often on posts here is that they are from people who can do what they were taught but unable to adapt to slightly different situations. They work by handbook standards but without true understanding. They are the ones who complained about trick problems in class.

Much of life IS a sequence of TRICK PROBLEMS.