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Join Date: Apr 2012
Posts: 5

Online Double Conversion UPS Output

04/18/2012 12:33 PM

What is the protection given by an online UPS of double conversion type, When there is a short circuit in the load side of UPS.

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#1

Re: Oonline Double Conversion UPS Output

04/18/2012 12:43 PM

Is this a trick question? Let's see.....If the overload on the UPS trips first due to the short, does that some how protect something up-line??? I guess it depends on what else is on the breaker for that feeder circuit.

Circuit breakers or fuses are about the only protection devices you have unless you count pulling the plug out of the wall.....

I would expect a short circuit would also prematurely age the output stage of the UPS a bit because it takes a finite amount of time for the protection device to do its thing.

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#2

Re: Online Double Conversion UPS Output

04/18/2012 1:22 PM

Actually it sounds like an interview question, perhaps Bernie will share his answer with us. If not here's a hint: None, the load side has shutdown, and should be smart enough to not try to continue to feed the fault; therefore the supply side never sees it. Is that the answer you gave, Bernie?

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#3

Re: Online Double Conversion UPS Output

04/19/2012 12:50 AM

If you incorporate a fuse/cb at the output side it will protect.

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#4
In reply to #3

Re: Online Double Conversion UPS Output

04/19/2012 12:43 PM

Yes agreed..., as you said, we need to incorporate fuses on downstream circuits to protect them.

What i want to know is, what are the standard features , we can expect in this type of (on line -double conversion) UPS systems to prevent overloads/ surge currents passing to the load. (in addition to the CB protection of the downstream circuit).

Thanks!

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#5
In reply to #4

Re: Online Double Conversion UPS Output

04/23/2012 7:54 AM

It all depends on what and where you buy. Many of these have electronic monitoring of the load. They don't have "standards" per se, they call them features. Of course, you can add your own breakers or fuses, but when the UPS determines that you are at the limit, it will shut you down.

This only makes sense when you consider that the "double conversion" means that the incoming power is converted to DC and then converted again to AC but with an electronically derived sineusoid waveshape. That is to say that there are no moving parts (exclusing any cooling fans).

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BERNY (1); NotUrOrdinaryJoe (2); pnaban (1); RAMConsult (1)

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