A transformer labeled for use with a specific voltage will work just as well at other voltages.

This calculator provides power delivered from a transformer tap when driven with other than the rated voltage.

Example:

You are installing a distributed system with very long lines.

To overcome line loss, you select a 140-volt system.

Which transformer tap will feed 10 watts to a loudspeaker with a 70-volt transformer?

1. Enter values for both “Voltage Rating of Transformer” and “New Voltage”

2. Either:

– Enter a value for “Tap Rating” to calculate the power output from the tap at the new voltage.

– Enter a value for “Power from Tap” to calculate the correct transformer tap to achieve the desired power at the new voltage.

Equation used to calculate the data:

Pactual = (Vnew squared / Vrated squared) * Prated

Where:
Prated = transformer tap value
Pactual = new power from tap
Vrated = voltage rating of transformer
Vnew = new voltage