Transformer tap changer calculator can be used to calculate secondary voltage for various tap positions based on actual primary voltage measured. User can then decide which higher/lower tap needs to be used to get the desired nominal voltage.

For detailed discussion on transformer tap changers refer to the link below.

Transformer Tap Changer: How to Select Transformer Taps?

Winding connections for transformer with four taps
Figure 1: Winding connections for transformer with four taps

From above equation, for a given primary voltage:

  • To increase secondary voltage, turns ratio must be decreased.
  • To decrease secondary voltage, turns ratio must be increased.

Link to: Transformer Current Calculator

Link to: Transformer Reactive Power Calculator