What Are Hysteresis and Eddy Current (Core) Losses?

Published 27 Aug 2026Updated 27 Aug 20266 min readIntermediateDesign
Quick answer — Hysteresis loss is the energy lost in repeatedly magnetising and demagnetising the core each cycle; eddy current loss is the energy lost to circulating currents induced in the core laminations. Both depend on the material and the flux density and voltage/frequency, and are the major part of the no-load (iron) loss. They are reduced by using grain-oriented or amorphous steel and thin, insulated laminations.
Contents
What are hysteresis and eddy current losses?

Hysteresis loss

It is proportional to the area of the hysteresis loop of the core material, so it depends on the material and the peak flux density. Lower coercivity steel (grain-oriented) reduces it.

Eddy current loss

Each alternating flux induces circulating currents in the core; they are reduced by using thin laminations with insulating coating between them and by choosing a low-loss material. Eddy loss scales with frequency squared and flux squared.

Practical effect

Together they make up the no-load loss that is present whenever the unit is energised. Reducing them improves efficiency and lowers the running cost, which is why better core steel is worth the extra cost.

References & standards

Related

Book seriesAcademy

Related manufacturers

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

Related components

Conductors & core steel
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.
Source transformers for this application

Submit an RFQ or browse manufacturers and components.

Submit an RFQ Get Verified