Kernverlust

Kernverlust refers to the energy that is lost as heat in the magnetic core of electrical devices such as transformers, inductors or electric motors when the core is exposed to alternating magnetic fields. It is composed mainly of two contributions: hysteresis loss and eddy current loss.

Hysteresis loss arises from the repeated realignment of magnetic domains as the magnetic flux density changes during operation. The energy dissipated as heat depends on the frequency of the magnetic excitation, the peak flux density, and the material’s hysteresis characteristics. Eddy current loss results from circulating currents induced within the conductive core by changing magnetic fields; these currents cause additional heating and increase with the square of frequency and the square of the flux density. Eddy current loss can be mitigated by using laminated cores, insulating between laminations, or employing materials with higher resistivity and reduced conductivity.

Material and design implications: To minimize Kernverlust, engineers select soft magnetic materials with favorable hysteresis properties, such as silicon steel, amorphous metals or ferrites, depending on the application and operating frequency. Laminations, grain structure, and thermal management influence the total core loss. In practice, hysteresis losses dominate at lower frequencies and flux densities, while eddy current losses become more significant at higher frequencies.

Measurement and standards: Core loss is specified for given drive conditions and is typically expressed in watts per unit mass (W/kg) or volume (W/L). Standardized testing follows established IEC or IEEE procedures for core loss characterization in transformers, inductors and other magnetic components.

Applications: Core loss is a key efficiency parameter in power transformers, inductors, reactors and electric machines, affecting heat generation, cooling requirements and overall energy efficiency.