## Calculate the power needed for your transformer easily

Which transformer is suitable for your application? How do you choose the right power class? Use this simple calculation to select the correct transformer. You should first determine the maximum current and voltage of your consumer in order to calculate the power of your consumer. After calculating the power value, you should select the next higher power class.

Your consumer’s voltage can be specified in three ways:

- AC voltage (1-phase)
- three-phase star (3-phase)
- Three-phase delta (3-phase)

With resistive load the calculation is as follows:

### AC voltage (1-phase)

**Calculation:** Power P =

max. Voltage U * max. Current I

*Example:*

The consumer has 200V and 6A.

230V * 6A = 1200VA = 1,2kVA

The correct transformer has 1.4 kVA.

### three-phase star (3-phase)

**Calculation:** Power P =

max. Voltage U * max. Current I * √3

*Example:*The consumer has 230V and 10A.

230V * 10A * √3 = 3984VA = ca. 4kVA

The correct transformer has 4 kVA.

### Three-phase delta (3-phase)

**Calculation:** Power P =

max. Voltage U * max. Current I

*Example:*The consumer has 400V and 10A.

400V * 10A = 4000VA = 4kVA

The correct transformer has 4 kVA.

A special case occurs if you want to operate a motor or inductive loads. In this case, you should note how much current the motor draws at starting moment and use this value as maximum current in the calculation. This is usually specified as a multiple of the rated current. For example, the starting torque can be specified as 3-5 In. This means that the motor draws 3-5 times the rated current when switched on. With a rated current of 10A one would therefore calculate with 50A.

You are welcome to use our calculator to find the correct power class for your application. Or ask our competent team for advice. We are happy to help you with the correct dimensioning of your transformer.