• piyushpandey

MemberSep 11, 2011

How to know the VA rating of a transformer

Hello to all

I am an electrical engineer and in an interview I was asked to tell the MVA rating of a transformer of few KV , and nothing was given means neither the power factor and nor the current , so I want to ask you people is there any way to determine the MVA rating of the transformer from the KV or vice-versa.

Please tell me with an example if possible.

Thank you
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Replies
• MemberSep 13, 2011

As far as i am concerned in XFR (transformer) both KV and MVA rating are mentioned. Both of them are essential because you can calculate rated current, rated impedence etc from this two value. So KV and MVA rating are independent variable. I don't know if there is practical function between them.

May be in practice there is some combination of this two. Which requires practical knowledge not mathematical issue.
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• MemberSep 18, 2011

not possible to tell the exact VA rating of the transformer given.
but if given the Voltage then u can decide whether it is coming inthe distribution or transmission or which range. then u can give an approx estimation of the KVA rating. ok
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• MemberSep 19, 2011

Arp
not possible to tell the exact VA rating of the transformer given.
but if given the Voltage then u can decide whether it is coming inthe distribution or transmission or which range. then u can give an approx estimation of the KVA rating. ok
hello arp

Actually I meant the same that how can you estimate the approximate value of the VA as ofcourse it is impossible to get the exact value of VA from the value of just of voltage and not the current.

So can you show this with an example, please.

Piyush Pandey
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• MemberSep 19, 2011

As an example, if the voltage rating of two sides are like 11 kv and 220 kv indicates it is a generating transformer so its rating is someewhat in range- 100to 200 MVA, if 15.75 kv then 300 MVA and if 21 kv to 220 kv then can be 600-900 MVA even.
if rating are 11 kv and 33 kv indicate its rating around 20 MVA.
if unit auxillary transformer (6.6/433) then should be around 2-4 MVA
if distribution one then should be around 25KVA to 10 MVA usually 1-10 MVA.
data taken from my internships done
if any furthur query u have, post here.
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• MemberSep 20, 2011

Arp
As an example, if the voltage rating of two sides are like 11 kv and 220 kv indicates it is a generating transformer so its rating is someewhat in range- 100to 200 MVA, if 15.75 kv then 300 MVA and if 21 kv to 220 kv then can be 600-900 MVA even.
if rating are 11 kv and 33 kv indicate its rating around 20 MVA.
if unit auxillary transformer (6.6/433) then should be around 2-4 MVA
if distribution one then should be around 25KVA to 10 MVA usually 1-10 MVA.
data taken from my internships done
if any furthur query u have, post here.
whats the math behind it? bro...
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• MemberSep 20, 2011

no math behind it just logic
what i know is the line voltage rating of the different rating alternators. from there u can know the kva rating of transformer if know the line voltage.
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