Low-loss silicon steel laminated core (for transformers)

Basic Structure of Transformers: Built on the “Three Pillars”

— Core as the Skeleton, Windings as the Blood Vessels, Bushings as the Connectors

Transformers operate by having two or more windings mounted on the same core column. Therefore, the core and windings form the fundamental structural components. For oil-immersed power transformers, additional elements include the tank, transformer oil, insulating bushings, and other structural accessories. The core and windings collectively form the transformer's body. Below, using common oil-immersed power transformers as an example, we focus on the core and windings.

Core

The core serves as both the magnetic path and mechanical skeleton of the transformer. It consists of core columns and a core yoke. Windings are mounted on the core columns, while the core yoke connects these columns to form a closed magnetic circuit. To minimize core losses from hysteresis and eddy currents, the core is typically constructed by laminating silicon steel sheets coated with insulating varnish on both sides, with sheet thicknesses ranging from 0.23 to 0.35 mm. Silicon steel sheets offer low core losses and high magnetic permeability.

Based on core structure, transformers are categorized into core-type and shell-type. Core-type structures feature windings encircling the core columns, while shell-type structures have the core enveloping the windings. Core-type designs are simpler, facilitating easier winding assembly and insulation, and are thus more widely used. Shell-type cores offer higher mechanical strength but involve more complex manufacturing. Consequently, this structure is typically reserved for low-voltage, high-current transformers or small-capacity telecommunication transformers.