If a transformer has a 480-volt primary and the supply voltage is 468 volts, which tap connection should maintain the rated output voltage?

To determine which tap connection should maintain the rated output voltage of the transformer when supplied with 468 volts instead of the rated primary voltage of 480 volts, it's crucial to understand how tap connections affect the voltage.

Transformers are designed to operate within specific voltage ranges, and tap connections allow for adjustments to accommodate variations in the supply voltage. The tap settings effectively modify the turns ratio of the transformer, which adjusts the output voltage to match what is needed under different supply conditions.

When the supply voltage is lower than the primary rated voltage, such as in this case where the supply is 468 volts instead of 480 volts, selecting a higher tap number from the series will increase the respective voltage ratio. This is because higher tap positions typically correspond to fewer turns of wire in the winding, allowing for a greater adjustment in output voltage.

The connection designated as "21/2FCBN" provides a suitable midpoint in terms of turns relative to the other options. This connection helps to raise the output voltage towards the rated output despite the lower supply voltage.

In essence, using the 21/2FCBN tap connection will ensure that the transformer delivers output voltage that is as close as possible to the rated voltage, thereby maintaining performance standards and ensuring that the