What happens to the efficiency of a transformer when the temperature rises excessively?

When the temperature of a transformer rises excessively, its efficiency decreases. This is primarily due to the increased resistance in the winding conductors and the additional losses associated with heat. As the temperature rises, there are two main types of losses that affect efficiency: copper losses and core losses.

Copper losses are related to the resistance of the wires, which increases with temperature. As the resistance increases, more energy is lost as heat during the conversion of electrical energy. Core losses also contribute to efficiency decline; these are due to hysteresis and eddy currents in the magnetic core, which can also increase with temperature.

Consequently, when the temperature of a transformer exceeds its designed operational limits, these losses compound, leading to a significant drop in overall efficiency. Therefore, heat management is crucial to maintaining transformer performance and ensuring optimal operation.