regeneration on customers' supply lines 1

[sibeen]

fab1961, I believe that when they talk about the short circuit power they mean the maximum fault current rating of the upstream transformer. In this case a 1 MVA transformer will have a maximum short circuit current of approximately 27 kA (I'm using a system voltage of 415 V) and therefore the short circuit power will be about 19 MVA, well beyond the 70 times recommended.

Work out what the transformer short circuit currents are for the minimum size installation that you envisage installing and work out the power from that.

I will say that it seems to be a badly worded 'specification'.

 

[jraef]

I used to work for Siemens and went through the training for this drive (but never actually commissioned one before I left). I was told that the requirement for a high power source was total, as in all the way back to the utility, not just from the local transformer. The reason they require that is because if you connect it to a local or portable generator with low relative power and low impedance, the harmonics that the active front end puts into the line gets extreme. you also must have somewhere for the power to go, as in a grid with other consumers attached.

Why someone would assume you can regenerate back into a small power source that may not have anywhere else to send the power is beyond me, It's not as though one can push the electrical power back into the generator and have it spit fuel back into the tank! But as can be witnessed in these forums, some people implement technology without thought to engineering.

So basically it's what we call a CYA statement. They are attempting to make people think and ask questions first, or eat it because they didn't when it doesn't work out. But I thought their wording left something to be desired, it may be a translation issue. Siemens' engineers in Germany tended to assume that readers would know the context and allow for translation errors. We had to learn not to take everything literally and ask for clarification a lot. You may be wise to do so as well. The local salesman may not know the answer, but keep pushing and you will find an engineer that will.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[fab1961]

sibeen, jraef
thank you very much.
Jraef I will follow your advice and try to get more info from local Siemens offices. One last question: do you think a filter may dampen the bad effects?

 

[jraef]

I believe that they have an EMI/RFI filter built-in, but they do not recommend line reactors on the regen option and I'm not clear on why (I remeber asking and was told "I'll have to get back to you on that", which never happened). Maybe if member Ozmosis sees this thread he can address it, he used to work there too and in fact worked directly for the Drives division. I'll shoot him a private message and ask him to check in on this thread.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376