Transformer Losses: Load Loss & No Load Loss

Every month we share an industry word or acronym to help translate some of the jargon from the electrical engineering world!

This month’s term is: Transformer Losses – Load Loss & No Load Loss

Transformer losses occur the whole time the transformer is powered. The current flows in a transformer winding and the alternating magnetic field in the core contributes to most transformer losses.

No Load Losses:

Transformer no-load loss is often called core loss or iron loss. The no-load losses in a transformer are primarily caused by losses in the core steel. However, it is the combined losses caused by eddy current, hysteresis, stray eddy current and dielectric losses that make up the no-load losses.

The size of the no-load loss is related to factors. These include transformer capacity, magnetic circuit structure, silicon steel sheet quality and depends on the unit loss of iron core material. With the voltage of the power supply being constant, the size of no-load loss remains the same value. You can often find this number on your transformer rating plate.

Load Losses:

The losses produced in the core are called no-load losses, meanwhile, the losses associated with the coils are called Load Losses.

Load losses are sometimes referred to as Copper Losses. The term copper losses are used regardless of whether the windings are made of copper or another conductor (typically aluminium). These losses are made up of heat losses and I²R (Current Squared times Resistance) losses. This loss is due to the primary and secondary winding resistance and is directly proportional to load, so if that increases the losses increase.

Reducing these losses:

The European Commission estimates that 2.9% of all energy generated across the EU and the UK is wasted through transformer losses.

In July 2021, the EU Ecodesign regulation came into place which made new regulations for load-losses on energy-related products. It aims to reduce the load losses of distribution transformers. Which in turn, will improve energy efficiency, and environmental compatibility and reduce CO2 emissions.