The largest loss in a transformer is typically the copper loss, also known as I²R loss. This type of loss occurs due to the resistance of the transformer windings to the flow of electrical current. When current passes through the windings, resistance causes heating proportional to the square of the current (I²) multiplied by the resistance (R). Copper loss accounts for a significant portion of the total losses in a transformer, particularly under full-load conditions where current flow is highest.
The loss that is maximum in transformers is often the core loss, which includes both hysteresis loss and eddy current loss. Hysteresis loss occurs because the magnetic materials in the transformer core (typically silicon steel) experience a loss of energy as they repeatedly magnetize and demagnetize in response to the alternating current. Eddy current loss, on the other hand, results from currents induced in the core material due to the changing magnetic field. Together, these core losses can be substantial, especially in large transformers operating at higher frequencies.
Transformers experience four main types of losses: copper loss (I²R loss), core loss (including hysteresis and eddy current losses), stray load loss, and dielectric loss. Copper loss occurs in the windings due to electrical resistance. Core losses refer to energy dissipated in the core material due to hysteresis and eddy currents. Stray load loss includes losses in structural elements, leakage fluxes, and mechanical vibrations. Dielectric loss involves energy dissipation in the insulating materials used within the transformer.
The total loss of a transformer encompasses all losses mentioned: copper loss, core loss (hysteresis and eddy current), stray load loss, and dielectric loss. These losses collectively reduce the efficiency of the transformer, as some of the input electrical energy is converted into heat rather than being transferred to the load as useful electrical power. Minimizing these losses is crucial for improving the efficiency and reliability of transformer operations, especially in applications where energy conservation and cost-effectiveness are paramount.
There are typically six losses considered in transformer operation: copper loss (I²R), core loss (hysteresis and eddy current), stray load loss, dielectric loss, load loss, and no-load loss. Load loss refers to the copper and stray load losses occurring under load conditions, while no-load loss comprises core and stray load losses when the transformer is idle but energized. These losses contribute to the overall inefficiency of transformers and are managed through design optimization, material selection, and operational strategies to enhance performance and reliability.