Why Is the Transformer Core Made of Laminations?

Look inside any disassembled transformer core and you'll find thin, stacked layers, not a single block of iron. This design isn't for ease of manufacturing — it's a clever engineering solution to a thermal loss problem called eddy currents.

The Problem: Eddy Currents

The iron core is an electrical conductor sitting within a varying magnetic flux, so induced currents form within the iron itself, circulating in closed loops called Eddy Currents. These currents do not transfer any useful energy; all they do is generate heat that wastes efficiency and raises the transformer's temperature.

The Solution: Thin Insulated Laminations

• The core is divided into thin laminations (fractions of a millimeter) insulated from one another by a layer of varnish or oxide.
• The insulation between laminations breaks up the large eddy current paths and confines them to very small loops within each lamination.
• Eddy current loss is proportional to the square of the lamination thickness, so the thinner the laminations, the more dramatically the loss drops.

Do Eddy Currents Disappear Completely?

No, a small value remains within each lamination, but it drops to a level that is economically and thermally acceptable. Materials engineers continue to improve this further by using grain-oriented silicon steel and even thinner laminations in high-efficiency transformers.