Transformer losses are primarily categorized as no-load losses and loaded losses. No-load losses, also called iron losses, are primarily caused by hysteresis and eddy current losses in the core. They are voltage- and frequency-dependent, but independent of the load current. Load losses, also called copper losses, are the heat loss caused by resistance when current flows through the coils and are proportional to the load current.
No-load losses (iron losses)
Definition:
When the secondary side of a transformer is open-circuited and the rated voltage and frequency are applied to the primary side, the power consumed by the transformer is the no-load loss.
Main cause:
Losses caused by hysteresis and eddy currents in the core under the influence of an alternating magnetic field.
Influencing factors:
Silicon steel sheet material, processing technology, core structure, voltage, and frequency.
Characteristics:
It is independent of the load current and is primarily affected by voltage and frequency. Iron losses remain essentially unchanged whether the transformer is unloaded or loaded.
Load losses (copper losses)
Definition:
When the transformer is operating under load, the heat loss caused by current flowing through the winding resistance.
Main cause: The winding resistance heats up. Higher currents increase the losses. Influencing Factors: Current, winding resistance, and temperature.
Characteristics: Copper losses increase with load current, typically reaching their maximum when the transformer is operating at full load.
Related Standards and Tests
National Standard: GB 20052-2013 specifies Class 1, Class 2, and Class 3 loss standards for transformers.
Industry Standard: JBT 3837-2016 specifies different loss parameters for different types of transformers, such as electrical steel strip transformers and amorphous alloy transformers.
Testing: A transformer no-load loss tester can measure no-load loss, load loss, short-circuit voltage, and other parameters.
Summary: No-load loss and load loss are the primary components of transformer losses. Understanding and controlling these two losses is crucial to transformer efficiency and economical operation.