Taps (Voltage Taps) — Transformer Glossary

Connection points on the transformer winding that allow the turns ratio to be adjusted, changing the output voltage.

Backelectrical

Taps (Voltage Taps)

Connection points on the transformer winding that allow the turns ratio to be adjusted, changing the output voltage.

Taps compensate for voltage variations in the supply network. De-energized tap changers (DETC) require the transformer to be switched off before adjustment — typically 5 positions (±2 × 2.5%). On-Load Tap Changers (OLTC) adjust while the transformer is energized, providing continuous voltage regulation. FCAN (Full Capacity Above Nominal) taps maintain full kVA rating at all positions above nominal. FCBN (Full Capacity Below Nominal) taps maintain rated kVA at and below nominal voltage. The tap range and number of steps are specified based on expected voltage fluctuations at the installation site.

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Nominal VoltageThe designated voltage of a power system or equipment, used as a reference value for the system's operating voltage.

OLTC (On-Load Tap Changer)Mechanical device that adjusts the transformer's turns ratio while energised and under load, allowing voltage regulation without interrupting supply.