Load losses (copper losses)
The Joule losses in the windings, which vary with the load.
Definition
Load losses, or copper losses, are the Joule-effect losses dissipated in the windings as the current flows through them. They result from the electrical resistance of the copper (or aluminium) of the coils and turn entirely into heat.
Their major feature is to vary with the square of the current: at half load, they are only a quarter of their full-load value. They are therefore small at no load and maximal at full load, unlike iron losses which are constant.
A transformer’s maximum efficiency is reached at the point where copper and iron losses become equal, generally around 50 to 70 % of load.
The ABL tip
Reducing copper losses relies on a larger or higher-quality copper section. For heavily used transformers, ABL Transfo oversizes the conductors to lower heating and losses.
