# Star-star-delta three-winding transformer

Canonical URL: https://eloragrid.ai/symbols/star-star-delta-three-winding-transformer
Publisher: Elora Grid
Updated: 2026-10-13
Lookup label: TX Y-Y-D
Drawing use: SLD, Schematic
Reference families: IEC, Manufacturer

A star-star-delta transformer includes two star-connected winding sets and a delta tertiary winding.

## What it represents

A star-star-delta transformer includes two star-connected winding sets and a delta tertiary winding. The schematic needs all three winding ratings and the intended tertiary connection.

## How to read it

- Trace the tertiary separately so its protection and terminal status remain visible.
- The preview is an original explanation of this function. Match the actual drawing convention to its legend and the selected equipment documentation.

## Information to show or reference

- State all three ratings
- Show both neutral arrangements
- Reference tertiary duty

## Important distinction

A delta tertiary is a third winding, not an alternative connection of the main secondary.

## Facts

- Drawing role: Winding connection
- Representation scope: Functional concept; not an official standard graphic or a product footprint
- Public vendor block reference: HXF1T15, VXF1T15 (Autodesk identifiers; not IEC symbol numbers)
- Identifier status: The short label is a functional lookup label, not an assigned IEC or IEEE symbol number. Any separately listed Autodesk code is a verified vendor block name.

## Public references

- [Power, potential and autotransformer symbols](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-C1FE1690-DBF4-4F69-85C4-28E41F0A6392.htm) — Autodesk. Public documentation of this equipment function or named vendor variant; the illustration is independently authored and is not the source graphic.
- [AutoCAD Electrical: Three-phase transformer connections](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-EB13DB13-01EE-4541-BED7-19B9001BE8FC.htm) — Autodesk. Public documentation of this equipment function or named vendor variant; the illustration is independently authored and is not the source graphic.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.