overfluxing

Overfluxing is a condition in electromagnetic devices, most commonly electrical transformers and inductors, where the magnetic flux in a ferromagnetic core exceeds the material's design limit. When the flux density approaches the core's saturation flux density, the core's permeability falls and the device ceases to respond linearly to the applied voltage, leading to distorted operation and excessive losses.

In a transformer, the peak flux is proportional to the volt-second product, V/(4.44 f N). For a given core, increasing voltage or reducing frequency raises the flux. If the flux exceeds the saturation region, the core saturates, causing a sharp rise in magnetizing current, higher core losses, audible noise, and distortion of the secondary voltage.

Common causes include overvoltage conditions, low frequency operation due to system disturbances, incorrect tap settings, energization inrush, transient events, and degraded core materials that reduce the effective saturation flux. Operating outside the intended voltage-frequency range increases the risk of overfluxing, especially during startup or fault conditions.

The effects of overfluxing include elevated core losses (hysteresis and eddy currents), overheating, reduced efficiency, audible buzzing, increased reactive current, waveform distortion, and potential insulation damage over time. Protection and mitigation strategies focus on maintaining flux densities well below the saturation limit through appropriate core sizing, voltage regulation, and temperature management.

Prevention also involves operational controls such as proper tap setting, controlled energization to limit inrush, and protective relays to detect abnormal volt-second conditions. See also magnetic saturation, volts-second product, transformer design, and core losses.