Welcome to Unitrafo's calculation help
Below you will find modules for useful calculations related to transformers. Change the pre-filled values to adapt the calculations to your needs. You can also download and save the calculation result as a pdf file.
Are you missing a calculation? Please let us know via our contact page.
Please note that the calculation results should only be used as an indication and should be checked in case of "live" use. Unitrafo is not responsible for any inaccuracies in the calculation results.
Calculate and compare costs of energy losses
You are free to change all variables in the calculations (blue numbers or sliders) to adapt them to your needs.
The calculations below do not take into account inflation, compound interest, any environmental taxes, etc.
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You are free to change all variables in the calculations (blue numbers or sliders) to adapt them to your needs.
The calculations below do not take into account inflation, compound interest, any environmental taxes, etc.
Alt 1
Alt 2
Alt 3
Transformer effect
The calculation tool below gives an indication of the minimum power (apparent power S) your transformer needs to be dimensioned for. Enter the current values for the connection voltage Un in volts and the current I (electrical load) in A. The number of phases is almost always 3, but the calculation tools can also be used for 1-phase.
Generally, choose a transformer that exceeds the apparent power. For example, if you get an apparent power of 799.5 kVA in the calculation, then choose a transformer of at least 800 kVA.
There are also other variables to consider when choosing a transformer. You are therefore always welcome to contact us to make the right choice.
Losses - Load
By finding out what load a transformer actually has, you can also calculate what losses you get in practice. This is therefore a very important parameter when choosing a transformer.
The no-load losses (Po) are always included so they are the same regardless of the load, which means that it is of course important that they are as low as possible. The load losses (Pk) vary exponentially with the load, which means that for example at 50% load you only have 0.25, i.e. 25% of the specified losses at this load. At low load, these losses are not as important as the no-load losses. At high load, however, the opposite applies, that the higher the load you have, the more important the load losses become.
With the tool below, you can easily see what losses you get at different load levels. A rule of thumb can be that you are at about 70% load level. Then you are using the transformer in a good way and get a good efficiency. What you should avoid is very high load or ditto low. In that case, you have usually chosen the wrong transformer.
Efficiency & Voltage drop
The efficiency of a transformer generally increases with size. A smaller electronic transformer can have an efficiency of around 50%, while a larger distribution transformer in an electricity network usually has an efficiency of 98% and above. Since 2015, the efficiency of larger transformers installed within the EU has been set by the so-called “Ecodesign Directive”. In short, this means that only transformers that meet the efficiency requirements may be installed.
A transformer’s voltage drop is important to know because it affects how well the electrical system in which the transformer is installed functions. Thus, a voltage drop that is too high can cause the voltage on the secondary side to be too low, which in turn can impair how connected equipment works, or cause, for example, motors not to start.
With the calculation tool below, you can easily calculate both the efficiency and voltage drop of the transformer you are interested in or may already own, but are thinking about replacing.