Efficiency — Transformer Glossary

The ratio of output power to input power, expressed as a percentage. Modern transformers achieve efficiencies of 98–99.5%.

Backelectrical

Efficiency

The ratio of output power to input power, expressed as a percentage. Modern transformers achieve efficiencies of 98–99.5%.

Transformer losses consist of no-load losses (core losses, constant regardless of load) and load losses (copper losses, proportional to load squared). Maximum efficiency occurs when no-load losses equal load losses — typically at 40–60% of rated load. Efficiency standards like DOE 2016/2024 and EU Eco Design mandate minimum efficiency levels that drive the use of premium core materials (CRGO, amorphous) and optimized winding designs.

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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.

Eddy CurrentsCirculating currents induced in conductive materials (core laminations, tank walls, structural parts) by time-varying magnetic flux.