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#1 bob

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Posted 15 May 2006 - 06:07 AM

Hi,

Two caps blew off on our dc bus and all the semiconductor fuses on the input supply burnt. The vsd is a 900 k W one.There is no fuse on the dc bus. I am afraid all the caps had been stressed and are not recoverable.
Any clue ?

Bob

#2 mariomaggi

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Posted 15 May 2006 - 06:17 AM

Dear Bob,
to add some useful comments it is necessary to know more details, like ambient temperature or humidity problems, capacitors age, service time (i.e.: too long period of inactivity), type of application, overvoltage/braking unit protection, type and manufacturer, and all info useful to state the true reason of this failure.

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Mario


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#3 bob

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Posted 15 May 2006 - 06:33 AM

Hi Mario,

Thanks for your help. The two caps blew off just after all the caps in the drive were replaced by new ones. It happened that two capacitors were wrongly installed with the polarities reversed. When the vsd was switched on, the semiconductor fuses blew almost at once.

Regards.

Bob

#4 mariomaggi

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Posted 15 May 2006 - 09:22 AM

Dear Bob,
no comments, someone has to pay for such mistakes!
There are no protections for all mistakes!
Regards
Mario

Mario Maggi - Italy - http://www.evlist.ithttps://www.axu.it


#5 kens

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Posted 15 May 2006 - 09:03 PM

Hi Bob, at least there were SCR fuses protecting the drive, if they weren't there you would probably have to replace your rectifier components as well. Because these fuses would have limited the energy of the fault it is possible that the remaining caps are unaffected, however a 900 kW drive is a fairly large and expensive piece of equipment so do you want to risk it? I guess that it all comes down to who is liable for the incorrect installation of the capacitors and whether it is possible to recover the cost of replacing all of them again?
I would have a spare pair of underwear on hand for the recomisioning just in case
An expert is one who knows more and more about less and less until he knows absolutely everything about nothing




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