Magnetic hysteresis is a phenomenon that occurs in magnetic materials, including those used in inductors and transformers. It refers to the lagging of magnetic flux density (B) behind the magnetizing force or magnetic field strength (H) in a magnetic material when the magnetizing force is varied.
When a magnetic material, such as iron or certain ferrites, is exposed to an external magnetic field, it becomes magnetized. As the intensity of the magnetic field increases, the magnetic domains in the material align, resulting in an increase in magnetic flux density. Conversely, when the external magnetic field is decreased, the magnetic domains may not fully return to their original state, and the magnetic flux density does not decrease proportionally.
This lagging effect causes a loop-like behavior in the material's magnetic characteristics when the magnetic field strength is cycled back and forth. The resulting loop is known as a hysteresis loop. The loop illustrates the relationship between magnetic flux density and the magnetizing force.
For inductors and transformers, magnetic hysteresis can have important implications. When an alternating current (AC) flows through the inductor or transformer winding, it generates an alternating magnetic field. As the magnetic field varies, the magnetic material in the core undergoes hysteresis, leading to energy losses in the form of heat.
These energy losses can be a concern in power applications since they reduce the efficiency of the inductor or transformer. To minimize hysteresis losses, materials with low hysteresis loop areas (such as soft magnetic materials) are chosen for the cores of inductors and transformers. Additionally, operating the magnetic components within their specified limits can help mitigate the effects of magnetic hysteresis.