Composition Requirements and High Mechanical Strength of EI Cores

EI Core Manufacturing and Structure

During the manufacturing process, EI cores are generally made of silicon steel sheets. Silicon steel is a type of steel containing silicon (also known as silica), with a silicon content ranging from 0.8% to 4.8%. Silicon steel is used for transformer cores because it is a highly permeable magnetic material. Within an energized coil, it can generate a high magnetic flux density, thereby allowing the overall size of the transformer to be reduced.

Regarding the core structure, when the core legs and yokes are not in the same plane, there are radial, involute, and symmetrical configurations. Because the magnetic flux is distributed more evenly in these designs, losses can be reduced. In contrast, planar-type cores have their legs and yokes in the same plane, offering high mechanical strength and excellent manufacturability.

EI cores are always laminated cores, assembled by stacking iron sheets. There are various forms of wound cores. Involute wound cores have relatively large air gaps between the core legs and yokes, which affects the no-load current; therefore, their capacity cannot be too small. However, since the leakage flux enters the plane of the silicon steel sheets perpendicularly—increasing additional losses—the sheet width should not be too large, meaning their capacity cannot be too large either.

An EI core mainly consists of three parts: the core body, fastening components, and insulation components.
① Core Body (Magnetic Conductor): Made of electrical steel sheets.
② Fastening Components: Including clamps, bolts, glass fiber binding tapes, steel binding tapes, and spacer blocks.
③ Insulation Components: Including clamp insulation, insulating tubes and pads, grounding plates, and base feet.