rautahäviöt

Rautahäviöt, also known as iron losses, are a phenomenon occurring in ferromagnetic materials, primarily in electrical transformers and rotating electrical machines. These losses are a result of the alternating magnetic flux that passes through the core of the device. They are divided into two main components: hysteresis losses and eddy current losses.

Hysteresis losses are caused by the continuous magnetization and demagnetization of the core material as the magnetic field direction alternates. Each time the magnetic field reverses, the magnetic domains within the material must reorient themselves. This process involves some energy dissipation due to friction between these domains, which is manifested as heat. The amount of hysteresis loss is dependent on the properties of the magnetic material and the frequency of the alternating flux.

Eddy current losses, on the other hand, are induced currents that flow within the conductive core material itself. As the magnetic flux changes, it induces electromotive forces (EMFs) according to Faraday's law of induction. These EMFs drive currents, known as eddy currents, within the core. Since the core material has some electrical resistance, these eddy currents dissipate energy in the form of heat. To minimize eddy current losses, the cores of transformers and electrical machines are typically constructed from thin laminations of material that are insulated from each other. This increases the overall resistance of the core, thereby reducing the magnitude of the eddy currents.

Both hysteresis and eddy current losses contribute to the inefficiency of electrical machines by converting electrical energy into heat, which is not useful work. Minimizing these losses through careful material selection and core design is crucial for improving the efficiency and performance of electrical devices.