Transformer Rating

Transformer Rating In kVA Explained

The transformer is not an electricity generation device. It works on the electricity transmitting by increasing or decreasing voltage or current from one place to another place. There are many kinds of transformers we see. All of them are not work the same efficiently.

We know the details about the transformer by the nameplate which is given on its body. The nameplate is considered a transformer rating. Transformer ratings specify VA (Volt-Amps) on its primary and secondary windings. The transformer rating shows that the maximum volume of its working efficiency.

What is Transformer Ratings?

Transformer ratings depend on the condition of the transformer’s temperature. The lower the rating of the transformer, the better. The product of volts and amperes is the transformer rating. The cooling system of a transformer can increase the transformer rating.

Why are Transformers Rated in kVA, not in kW?

Transformer rating measured in kVA. To understand it clearly before you know the equation of kVA and kW. kVA = kV*A. Here kV means the multiplication of voltage and current. When calculating the medium of kVA, then the power factor is not taken the account. It means that kVA is independent of the power factor.

kW= kW*A*PF. Here the equation means the multiplication of voltage, current, and power factor. Two of the equation shows that only the power factor is the difference between the equations. We know the transformer does not work based on the power factor.

It is the main reason for measuring kVA. If the transformer is not rated in kV, it creates much confusion in reading its connection and output criteria.

Calculate Transformer Ratings

The calculation of the transformer rating is straightforward. It depends on the voltage and current. kVA is also known as VA, kVA, and MVA but not kW. When a transformer work, it creates heat. Transformer ratings depend on the turn number of coils and the insulating oil.

For any transformer, the input voltage is the summation of the output voltage and losses. The calculation of the rating equation of the transformer is kVA= kV*A.

Transformer Rating Measurement

By the equation, the single and three phages transformer rating measurement is straightforward. There are some similarities between the two equations. The whole process is given below:

Single Phage

This value is obtained by multiplying the kilo volt-ampere by 1000 and dividing by the total voltage. The function is below:

Full load current= (kVA*1000)/ Voltage

Three Phages

Kilo multiplied by 1000 with volt-amperes the values obtained by dividing the result obtained by voltage, and 1.73 can be found. The equation is mentioned below:

Full load current= (kVA*1000)/ (1.73*Voltage)

Transformer Rating Measurement


The transformer does not generate output value. Complete works of it depend on the primary current and voltage. The transformer ratings show the transformer’s working details. Transformer rating measured on kVA because it works doesn’t depend on power factor.


About the Author: Mehedi Hasan

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