The largest loss in a transformer is typically the copper loss, which consists of two components: ohmic or I²R losses in the windings and stray losses.
- Ohmic Losses (I²R Losses): These losses occur due to the resistance of the copper conductors in the transformer windings. When current flows through the windings, it encounters resistance, resulting in the generation of heat. The formula for calculating ohmic losses is I²R, where ‘I’ is the current flowing through the winding, and ‘R’ is the resistance of the winding. Since power loss is proportional to the square of the current, higher currents lead to increased ohmic losses.
- Stray Losses: Stray losses, also known as eddy current losses and hysteresis losses, occur due to the interaction of the transformer’s magnetic field with the structural components of the transformer, such as the core and supporting structures. These losses are associated with the magnetic properties of the materials used in the transformer construction. Eddy current losses result from circulating currents induced in the metallic parts of the transformer, causing resistive heating. Hysteresis losses occur as a result of the magnetic domains in the core material constantly changing direction with the alternating magnetic field, leading to energy dissipation in the form of heat.
While stray losses are significant, especially in large power transformers, their contribution to total losses is often overshadowed by the ohmic losses. Ohmic losses increase with the square of the current, and they dominate when the transformer is loaded at high percentages of its rated capacity.
Efforts to minimize losses in transformers include using high-conductivity materials for windings, optimizing core design, and employing materials with low hysteresis and eddy current losses. Additionally, transformers are often designed to operate at high efficiency levels, especially when they are part of the energy distribution infrastructure, where minimizing losses is critical for overall system efficiency and energy conservation.
In summary, the largest loss in a transformer is generally the copper loss, comprising ohmic losses in the windings and stray losses associated with the magnetic properties of the core material. Minimizing these losses is essential to enhance the efficiency and overall performance of the transformer in electrical power systems.