What Is a Scott Transformer?

Published 27 Aug 2026Updated 27 Aug 20265 min readAdvancedApplications
Quick answer — A Scott transformer (Scott connection) uses two single-phase transformers, connected in a T, to convert a three-phase supply into a balanced two-phase supply, or vice versa. The two units are wound with a specific 50% and 86.6% tapping arrangement so the two-phase outputs are in quadrature. It is used in some traction, special loads and older conversion schemes.
Contents
What is a Scott transformer connection?

The connection

Two transformers, a main and a teaser, are connected so the teaser is fed from a mid-tap of the main. With the correct windings the three-phase inputs produce a balanced two-phase (or two-phase to three-phase) output.

Where it is used

Historically for two-phase-to-three-phase conversion, in some traction systems and specialised industrial loads, though less common today.

Why it matters

It teaches the principles of three-phase-to-two-phase conversion and is still specified in certain niche applications where a two-phase supply or a phase split is needed.

References & standards

Related

Book seriesAcademy

Related manufacturers

Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Virginia Transformer Corp · Pennsylvania Transformer Technology

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Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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