Step-Lap Core Joint — Transformer Glossary

Core lamination stacking technique where adjacent layers are offset in steps rather than aligned, reducing air gaps at joints.

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Step-Lap Core Joint

Core lamination stacking technique where adjacent layers are offset in steps rather than aligned, reducing air gaps at joints.

Step-lap joints reduce no-load losses by 10–15% and magnetizing current by 15–25% compared to conventional mitre (45°) joints. The technique distributes the air gap across multiple lamination layers, reducing local flux concentration and noise. Step-lap is standard in all ETS power transformers and premium distribution transformers. The number of steps (typically 5–7) balances manufacturing complexity against performance improvement.

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Transformer CoreThe laminated magnetic circuit that provides the path for magnetic flux between the primary and secondary windings.

Core Loss (No-Load Loss)Power dissipated in the transformer core due to hysteresis and eddy currents. Present whenever the transformer is energized, regardless of load.