VA Rating On Current Transformers

Why?

Is this an original marking? Specification plate?

Double check with the manufacturer.

why you need to cross check that?

basically VA rating of CT is the value of burden(output load) a CT can withstand,

i.e. cable & meter

..."Burden test is to ensure the connected burden to CT is with in the rated burden, identified on the nameplate.

Injected the rated secondary current of the CT, from CT terminals towards load side by isolating the CT secondary with all connected load and observe the voltage drop across the injection points. The burden VA can be calculated as

Burden VA = Voltage drop x rated CT sec. Current."

http://electrical-engineering-portal.com/testing-commissioning-current-transformer

Yes. The manufacturer can. It's only a phone call, though the manufacturer has already helped by marking the VA rating on the equipment and publishing the VA rating on the datasheet, for all to use, that accompanies it.

_{This is one of those "D'oh" threads [reference the cartoon series, The Simpsons].}

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there is no check, its a math calculation a child can do

That's assuming that the markings on the tag on the transformer are correct. I assumed the OP didn't believe the manufacturer got it right on his transformer. Mistakes do happen. So the question is how to determine if the 5VA as the manufacturer says, is correct, not how to multiply V * A.

once energized mistakes show up immediately as smoke

Yes and I also assumed the OP did not want to see the magic smoke. Perhaps the OP is scared because of the extremely low rating. Old hands at this just go ahead and throw the switch - newer ones fret over low power rated items.

Some examples have produced a smoke delay . . . even so the smoke will come out.

classic dumb question, we must be bored to even respond

Ding, ding, ding, ding!!! Ladies and gentlemen, we have a winner!!!! How come I can never close my eyes until I get down to reading emails? especially on Friday, after lunch, with re-arranging my bookshelf being my assigned priority #1 for the afternoon?

It was either this or mow the lawn for me.

You have grass in Arizona?

And oranges too. Here it is mid-May and they're still falling off our trees.

You should see the golf courses around here.

Very good. I'm in the middle of a stretch of 5 major skid projects with the customer supplying the panels. Not much more to do once you've spec'd and ordered the instrument cables, and made fancy color coded Excel spreadsheets with cable number for heat shrink labels/cable model and length/OD size/panel location/landing terminals/numbers for heat shrink labels for individual conductors so the electricians that will wire them don't need the drawings from the customer's panel builder anymore. Yeah - a bit slow right now - need some more CR4 posts to work on. Tell Fredski to do another "What is this?"

Test question, or job interview question?

The load, or burden, in a CT metering circuit is the (largely resistive) impedance connected to the secondary winding. Typical burden ratings for IEC CTs are 1.5 VA, 3 VA, 5 VA, 10 VA, 15 VA, 20 VA, 30 VA, 45 VA & 60 VA. ANSI/IEEE burden ratings are B-0.1, B-0.2, B-0.5, B-1.0, B-2.0 and B-4.0.
Courtesy of Midwestern Current Transformer FAQ's

These ratings are industrial standards, can you give us a reason why you feel the need to question it?

Why in the world would you want to check the BURDEN rating of a CT without checking its accuracy. The reason for this is that you are way over your head dealing with a simple item like a CT. Saying "5VA" is only half the information, . . . the full answer may be . . . the accuracy is 0.3% at a burden of 5VA, . . . or something similar.

Anyway, . . . no one checks the burden of a CT, . . . they would rather check the accuracy with the CT loaded with a particular burden. One would conduct an accuracy test and from the test results determine what accuracy at what burden the CT is capable of. Thus, for example, the CT may have an accuracy of 0.3% at a burden of 5VA, as well as an accuracy of 0.6% at a burden of 12.5VA, . . . as well as an accuracy of 1% at a burcen of 25VA.

In a transformer, VA is the apparent rated capacity... and it is the vectorial sum of the reactive power together with the real power capacity rating of that device..

Depending on your load, the power factor of the 5 VA rated CT may approach unity (almost 1 theoretically) only if your load is purely resistive! The power factor may also be lower than the rated power, if subjected to a load that is partly inductive, like a motor(s)!

In testing your device, you can try using an equivalent rated incandescent bulb, (which is almost resistive), as the load. Observe and record the temperature rise of the transformer over an acceptable time frame.

If the observed temperature is high, then the device maybe overrated....it cannot safely carry whatever its rated capacity!

you're asking a VA question, what circuit voltage?take your va and divide it by the applied voltage to get an amp draw rating. so on a 30 va former in a 24v circuit you have a max 1.25 amp rating/draw/fuse size/