Transformer Tap Calculator

Determine optimal tap position for voltage regulation.

Measured supply voltage
Target load voltage

Voltage Regulation Formula

VR% = %Z × (R×cosθ + X×sinθ) × Load%/100

Where R and X are per-unit resistance and reactance components of impedance.

Transformer Tap Changer Types

De-Energized Tap Changer (DETC)

  • Adjusted only when transformer is off
  • Typically +/- 5% in 2.5% steps
  • 4-5 positions common
  • Lower cost, simpler design
  • Used for seasonal adjustments

On-Load Tap Changer (OLTC)

  • Changes taps while energized
  • Typically +/- 10% range
  • 17-33 positions common
  • Automatic voltage regulation
  • Higher cost, requires maintenance