How to Size a Transformer
- Transformer size is determined by the kVA of the load.
- Load voltage, or secondary voltage, is the voltage needed to operate the load.
- Line voltage, or primary voltage, is the voltage from the source.
- Single-Phase has two lines of AC power.
- Three-Phase has three lines of AC power, with each line 120 degrees out of phase with the other two.
- kVA is kilovolt ampere or thousand volt ampere. This is how transformers are rated.
To determine the size of the transformer you need, determine the following requirements for your transformer:
- Load Voltage
- Load Current/Amps
- Line Voltage
Next, determine if your application is single-phase or three-phase, and use this corresponding formula:
The kVA of the transformer should be equal to or greater than the kVA of the load to handle present requirements and to account for future expansion.
As a service to you, we offer a transformer specifier to help you find your transformers quickly and easily.
Calculate your kVA
Use the calculating forms below if you know your Load Voltage and Load Current.