How to Calculate the Difference in Step Down Transformer Potential

You must know the ratio of turns between the transformer primary and the transformer secondary to calculate the output potential.

A step-down transformer is an electrical device that is used to reduce AC voltage while maintaining the same total power. The voltage differential -- or "potential" -- that is applied to the transformer's primary windings is converted into a transient electromagnetic field. This field passes through the transformer core, and is reconstituted at the transformer secondary as a smaller voltage.



The number of windings in a step-down transformer's primary is greater than the number of windings present in the transformer's secondary. The windings ratio between these two transformer sections determines how much the voltage is stepped down.

Things You'll Need

• Pen or pencil
• Paper
• Calculator
• Step-down transformer

Instructions

1. Obtain the windings ratio of the transformer. This number is often printed on the transformer case, and will take the form of "primary:secondary." For example, a "2:1" transformer will have twice as many windings in the primary as it has in the secondary.

2. Divide the secondary number by the primary number. For a 2:1 transformer, this number is 1/2, or 0.5.

3. Multiply the input voltage you intend to apply to the transformer by the number you calculated in the previous step. For example, if you apply 12 volts to a 2:1 transformer's primary, you will obtain 6 volts across the transformer's secondary.

Tips & Warnings

• Some transformers are labeled according to the voltages they are intended to convert. For example, a 240v/120v transformer is intended to be used to convert a 240-volt power supply into a 120-volt output signal.

References

• Georgia State University: Transformers