just wondering the possibility of bonding two 5MV mains

yes it is very much possible

If you are asking this type of question you are obviously in the wrong job. News groups are for discussions and leads to different ideas, not for training professional engineers.

If you get your scenario wrong, visions of Hiroshima come to mind.

John G.

Interesting how you jump to conclusions as to what I do for a living, I gave no mention of my profession, you merely made an assumption which is incorrect. As for understanding the amount of energy involved I certainly do and respect it fully. I merely was trying to understand if the possibility exists, and if it indeed does and it is backed by common engineering practices then my next move would be to get a professional to do the job of design ect.

Marco

Interesting how you jump to conclusions as to what I do for a living, I gave no mention of my profession, you merely made an assumption which is incorrect. As for understanding the amount of energy involved I certainly do and respect it fully. I merely was trying to understand if the possibility exists, and if it indeed does and it is backed by common engineering practices then my next move would be to get a professional to do the job of design ect.

Marco

If you want to parallel up two transformers then they must have the same % impedence, they need to have the same vectoring the same phase rotation. It is not absolutely essential for them to have same rating, but if they are not the same then there can be imballancing problems. Protection also has to be re-graded and one of the biggest problems you would face is that fault current would double (as the impedence would half). Having said all this, a properly designed system can be run in parrallel, but a system that is not designed to function this way would present problems.

We had a problem with a transformer over-heating for various reasons (harmonic problems, imbalenced loads, warm switch room). Our engineer at the time paralleled up this transformer with an identical transformer which had a low load. After a few hours it became obvious that all was not well. Both transformers buzzed loudly, over-heated and the curent to earth increased as well. Our engineer returned the system to normal soon after.

|> This is may sound crazy but if I have two 4160V 3phase transformers at |> my location each rated for 5MVA is it possible to bond the outputs |> together to drive a 9MVA variable frequency drive. |>

|> Just curious |>

|> Marco | | | If you are asking this type of question you are obviously in the wrong job. | News groups are for discussions and leads to different ideas, not for | training professional engineers. | | If you get your scenario wrong, visions of Hiroshima come to mind. | | 9MVA is quite a destructive amount of power needing real engineering | training.

If the circuit is designed for 9MVA, imagine the fault current available.

| Interesting how you jump to conclusions as to what I do for a living, | I gave no mention of my profession, you merely made an assumption | which is incorrect. | As for understanding the amount of energy involved I certainly do and | respect it fully. | I merely was trying to understand if the possibility exists, and if it | indeed does and it is backed by common engineering practices then my | next move would be to get a professional to do the job of design ect.

If you already have the transformers, they may, or may not, be usable for this. Such a thing would need a lot of trained planning all the way through careful testing before energizing, and very close monitoring energized and loaded for a while to be 100% sure. This should all be worked out by the professional you hire, after he determines if your situation even allows it (for example unlike transformers are probably a no-go).

If you don't have the transformers already, I'd think you'd look at getting a single 10MVA one or whatever your whole needs are.

Imagine the cable selection headaches!

..

Thankyou all for your input. My sense now is even though possible there are many caveats as to the proper implementation which scares me at these levels not to mention that my experience has taught me that the more exotic the solution the more $$$ so best to play it safe in this case. Again thanks to all who provided commentary.

Marco

Thankyou all for your input. My sense now is even though possible there are many caveats as to the proper implementation which scares me at these levels not to mention that my experience has taught me that the more exotic the solution the more $$$ so best to play it safe in this case. Again thanks to all who provided commentary.

Marco

It's been done but the load sharing depends on the relative impedances of the two transformers and it is easy to overload one of the transformers if the impedances don't match. 9MVA on 2- 5MVA units doesn't leave enough capacity room to be sure. As mentioned elsewhere there are sufficient problems and this is where you get professional help -play it safe.