# Transformer Sizing Calculator

Created by Luciano Mino
Last updated: Sep 05, 2022
Table of contents:

Our transformer size calculator can find the right transformer size (single or three-phase) for any load you require!

Within this short text, you will learn:

• The working principle of transformers;
• How to size a single-phase transformer;
• How to calculate transformer size for a three-phase transformer; and
• More!

Keep reading to learn about all the features of this transformer kVA calculator.

## How do transformers work?

Transformers are electrical devices that transform voltages. They can bring the voltage up or down depending on their purpose.

Transformers work in the following way:

1. Alternating current (AC) flows through a coil of wire, producing a changing magnetic field.
2. A magnetic core leads this magnetic flux through another coil of wire which has a different number of turns than our first coil.
3. Electromagnetic induction produces an electromotive force, a voltage difference, on the second coil.
4. According to the number of turns, this transformer will create a step-up or step-down in voltage.

## How to size a transformer

We size transformers based on the load they should power and use kVA, kilo volt-ampere, to rate them (what is kVA?). A higher transformer's kVA means a higher current and voltage output.

To find the appropriate size for our load, we need two things:

• $I$, the current of our load; and
• $V$ our load's voltage requirement.

Then, all we need to do is plug these parameters into the respective transformer formula.

For a single-phase transformer, we have:

$\text{kVA}= \frac{I\cdot V}{1000}$

and for a three-phase transformer:

$\text{kVA} = \frac{I\cdot V\cdot \sqrt{3}}{1000}$

🙋 This transformer sizing calculator operates with both equations: it works as a single-phase transformer kVA calculator and as a 3-phase transformer calculator! Simply select the transformer type at the top of this tool and type in your parameters.

## How to use our transformer sizing calculator

Using this tool is straightforward:

1. Select the type of transformer (single or three-phase).
2. Input your load's current requirement.
3. Input your load's voltage requirement.
4. Our calculator will automatically output the minimum kVA rating for the transformer. Give it a try!
Luciano Mino
Transformer type
Single-phase
Load current (I)
A
Load voltage (V)
V
Minimum kVA required
kVA
You can include spare capacity with the advanced mode!
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