Y–Delta Resistor Network Calculator
Edit any delta resistor Ra, Rb or Rc to calculate the wye arms; edit any wye arm R1, R2 or R3 to calculate the delta network.
Inputs and reverse calculation
Calculated results
| Delta Ra | 300 Ω |
|---|---|
| Delta Rb | 300 Ω |
| Delta Rc | 300 Ω |
| Wye R1 | 100 Ω |
| Wye R2 | 100 Ω |
| Wye R3 | 100 Ω |
How to interpret the result
A three-terminal resistor network can be transformed between wye and delta while preserving its terminal resistance. In a balanced network, each delta edge is three times a wye arm.
Formulas and units
Σ = Ra + Rb + Rc; R1 = RbRc/Σ, R2 = RaRc/Σ, R3 = RaRb/Σ. In reverse, S = R1R2 + R2R3 + R3R1; Ra = S/R1, Rb = S/R2, Rc = S/R3.
Worked example
Delta to wye: Ra = Rb = Rc = 300 Ω gives R1 = R2 = R3 = 100 Ω. Wye arms of 300 Ω instead give delta edges of 900 Ω; the direction matters.
Scope and limitations
Use finite, strictly positive real resistances. Delta edge Ra is opposite the terminal of wye arm R1, with the other labels following the same rule. The wye center is not an external terminal. Zero-ohm and open-circuit limits require separate analysis; division by zero is rejected instead of reproducing the App result.
Common questions
Is this a star–delta motor starter calculator?
This converts equivalent three-terminal resistor networks. It does not calculate motor starting current, winding ratings or contactor connections.
How is the conversion direction selected?
The last edited group controls the direction: Ra/Rb/Rc selects delta to wye; R1/R2/R3 selects wye to delta. Calculations retain internal precision while displayed values use three decimals.
Related tools
Formula and data sources
Rebuilt from the extracted Electrodoc Pro 5.2 specification. Added, inferred and corrected behavior is identified in the limitations. Updated 2026-11-13.