Documentation sections

Delta–Wye (Star–Delta) Conversion Calculator

POSThttps://rftools.io/api/py/v1/calculate

Slug delta-wye-conversion. Convert resistor networks between delta (Δ) and wye (Y / star) configurations. Supports bidirectional Delta→Wye and Wye→Delta conversion with exact formulas. Essential for three-phase power analysis and bridge circuit simplification.

Inputs

Send every one of these in inputs, in the units shown. Most are required: a call without one is refused (400) and costs nothing; one the calculator can do without takes the default shown. An input outside its range is still computed and flagged in the provenance.

Inputs of delta-wye-conversion
Name	Unit	Range	Default	Description
conversionDirnumber	none	0 … 1	0	Conversion DirectionOne of: 0 Delta → Wye · 1 Wye → Delta
ranumber	Ω	0.001 … 1000000000	10	Ra (Δ) or R1 (Y)
rbnumber	Ω	0.001 … 1000000000	20	Rb (Δ) or R2 (Y)
rcnumber	Ω	0.001 … 1000000000	30	Rc (Δ) or R3 (Y)

Outputs

Returned in values, by key. A value that is unbounded or undefined is null.

Outputs of delta-wye-conversion
Field	Unit	Description
r1headline	Ω	Delta→Wye: R1 = Rb·Rc/(Ra+Rb+Rc) — R1 opposite Ra
r2	Ω	Delta→Wye: R2 = Ra·Rc/(Ra+Rb+Rc) — R2 opposite Rb
r3	Ω	Delta→Wye: R3 = Ra·Rb/(Ra+Rb+Rc) — R3 opposite Rc
rdA	Ω	Wye→Delta: Ra = (R1R2+R2R3+R3R1)/R1 — Ra opposite R1
rdB	Ω	Wye→Delta: Rb = (R1R2+R2R3+R3R1)/R2 — Rb opposite R2
rdC	Ω	Wye→Delta: Rc = (R1R2+R2R3+R3R1)/R3 — Rc opposite R3

Calling it

Calculate: one call, the request and response in full, and its errors.
Batch: this calculator with others, or a sweep, in one request.
Solve for a target: the value of one input that brings an output to a target.

curl -X POST https://rftools.io/api/py/v1/calculate \
  -H "X-API-Key: $RFTOOLS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "slug": "delta-wye-conversion",
    "inputs": {
      "conversionDir": 0,
      "ra": 10,
      "rb": 20,
      "rc": 30
    }
  }'

import rftools

client = rftools.Client()  # reads RFTOOLS_API_KEY, or the key `rftools login` saved

result = client.calculate("delta-wye-conversion", {"conversionDir": 0, "ra": 10, "rb": 20, "rc": 30})
print(result.values)
print(result.warnings, result.provenance.formula_ref)

const response = await fetch("https://rftools.io/api/py/v1/calculate", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.RFTOOLS_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "slug": "delta-wye-conversion",
    "inputs": {
      "conversionDir": 0,
      "ra": 10,
      "rb": 20,
      "rc": 30
    }
  }),
});
console.log(response.status, await response.json());

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	body := []byte(`{
	  "slug": "delta-wye-conversion",
	  "inputs": {
	    "conversionDir": 0,
	    "ra": 10,
	    "rb": 20,
	    "rc": 30
	  }
	}`)
	req, err := http.NewRequest("POST", "https://rftools.io/api/py/v1/calculate", bytes.NewReader(body))
	if err != nil {
		panic(err)
	}
	req.Header.Set("X-API-Key", os.Getenv("RFTOOLS_API_KEY"))
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(res.Status, string(out))
}

application/json

{
  "slug": "delta-wye-conversion",
  "values": {
    "r1": 10,
    "r2": 5,
    "r3": 3.3333333333333335,
    "rdA": 10,
    "rdB": 20,
    "rdC": 30
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:delta-wye-conversion",
    "version": "api@3f2c1a9b04de",
    "formulaRef": "Hayt & Kemmerly, Engineering Circuit Analysis, 8th ed.",
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "conversionDir": {
          "min": 0,
          "max": 1,
          "unit": ""
        },
        "ra": {
          "min": 0.001,
          "max": 1000000000,
          "unit": "Ω"
        },
        "rb": {
          "min": 0.001,
          "max": 1000000000,
          "unit": "Ω"
        },
        "rc": {
          "min": 0.001,
          "max": 1000000000,
          "unit": "Ω"
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "conversionDir": 0,
      "ra": 10,
      "rb": 20,
      "rc": 30
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "conversionDir"
      ],
      "msg": "Input should be a valid number, unable to parse string as a number",
      "input": "abc"
    }
  ]
}

An input sent as text. Nothing was counted.

{
  "detail": "More than 120 requests in 60 seconds from this address.",
  "errorKind": "rate_limited",
  "limit": 120,
  "windowSeconds": 60,
  "upgradeUrl": "https://rftools.io/pricing/"
}

Too many requests in a minute, with Retry-After.

Same inputs on the calculator pageDelta–Wye (Star–Delta) Conversion Calculator, at these values