What Is the Difference Between a Reactor and a Transformer?

Published 27 Aug 2026Updated 27 Aug 20265 min readIntermediateGrid
Quick answer — A transformer transfers power between two circuits with a defined voltage ratio; a reactor (shunt or series) is an inductive device that absorbs or regulates reactive power with no secondary (or a fixed coupling) — it is essentially an inductor, often a single-winding device. A shunt reactor absorbs reactive power to control voltage; a series reactor limits current/rating. Transformers step voltage; reactors absorb reactance.
Contents
What is the difference between a reactor and a transformer?

Transformer

A two-winding (or autotransformer) device that transfers power with a voltage ratio, isolating or stepping the voltage, with losses, tappings and a magnetic coupling.

Reactor

A mainly inductive device — a shunt reactor absorbs reactive power to hold the voltage, a series reactor limits current and fault level; it has a low magnetic coupling and no true secondary.

How to tell

A transformer steps the voltage and has a rating in MVA and a ratio; a reactor is rated in MVAr (shunt) or ohms/current (series) and its main effect is on reactive power or fault current, not voltage transformation.

References & standards

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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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