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

asked 9/11/2011

3 Answers

Generally Transformers are designed as per the requirement of the consumer or demand factor, it all depends on the winding, loses and short circuit current, the main Loses of the transformer is copper loss ie,of the winding that is A (current) and core losses( iron loss/hysteresis)  are nothing but V (voltage) and now rating of the transformer are from 0.001 MVA  to 2500 MVA all depends upon the application, While generating Power the Voltage is generated to 11 KV and  then it is step up with Power transformer as per the demand, an the same power is transmitted by transmission line keep in view of voltage drop.

answered 8/10/2013 Sathya Narayana JE E/M 46
Sathya Narayana JE E/M
What is the maximum and minimum MVA ratings of following transformers used in transmission and distribution of power-

1 .66KV/11KV transformers                                                                                                                                      2.132KV/11KV Transformer

What is the criteria on which the manufacturers decides the MVA rating?

answered 7/6/2013 ram31 66
Not really. Choose any kV and look at a manufacturers catalogue and there will be a large range of MVA. The only thing you can probably say is that the bigger the kV, the larger that transformer as generally engineers will increase the voltage to transmit more power.

I'm reading a Siemens guide and they have typical ranges of 100 kVA to 30 MVA for what they call Small Power, 40 to 250 MVA for Medium Power and 200 to over 1000 MVA for Power Transformers.
answered 9/12/2011 Steven McFadyen 246
Steven McFadyen

Your Answer

In order to provide an answer to this question, you must Login

I am flagging this question because...

10 inform moderator flags remaining

I am deleting this question because...

I am flagging this answer because...

10 inform moderator flags remaining

Flagging a Post

You have already flagged this post. Clicking "Remove Flag" below will remove your flag, thus reducing the count by one as well.

I am deleting this answer because...

HTML Symbol Entities

HTML supports a variety of entity symbols which can be entered using either numbers or an entity name.  The number or name is preceded by the ‘&’ sign...

Lightning Risk Assessment (IEC 62305)

IEC 62305 'Protection against lightning' requires a risk assessment be carried out to determine the characteristics of any lightning protection system...

Electric Motors

Collection of links to various places with useful motor information. I’ll try and return to the page every now and again to update it with any motor notes...

Back to Basics - Ohm’s Law

Electrical engineering has a multitude of laws and theorems. It is fair to say the Ohm's Law is one of the more widely known; it not the most known. Developed...

Lightning Protection and Earth Electrode Resistance

Most installations involve some form of lightning protection system which is connected to an earth electrode.  The function of the earth electrode is to...

What is a rectifier transformer?

I've recently come across this question a couple times browsing the internet. Decided to give a quick answer here. A rectifier transformer is a transformer...

Induction Motor Calculator

Just added a page to the tools, which will allow you to calculate the synchronous speed, slip and rated torque for an induction motor. Not a particularly...

Fault Calculations - Typical Equipment Parameters

A frequent problem in fault calculations is the obtaining of equipment parameters.  While it is always preferable to use the actual parameters of the equipment...

Power Factor

Power factor is the ratio between the real power (P in kW) and apparent power (S in kVA) drawn by an electrical load. The reactive power (Q in kVAr)...

How a Digital Substation Works

Traditionally substations have used circuit breakers, current transformers (CT), voltage transformers (VT) and protection relays all wired together using...

Our website uses cookies so that we can provide a better experience.
To learn more about what cookies are and how to manage them visit