High permeability
High permeability refers to the permeability of a material in the presence of a magnetic field. Permeability is the ability of a material to respond to a magnetic field and is usually expressed as the ratio of magnetic flux density to magnetic field strength. High permeability means that the material is able to transfer flux more efficiently under the action of a magnetic field and is therefore important for use in electromagnetic devices.
A high permeability material is a ferromagnetic material with a magnetic permeability of approximately 100 or more. They are also called soft magnetic materials. These materials require high magnetic permeability, high saturation magnetic induction strength, high resistance, low loss, good stability, etc. Among them, especially high permeability and low loss are the most important.
High permeability materials show better performance in alternating magnetic fields, because in alternating magnetic fields, the magnetic flux density and magnetic field strength vary with time, so the permeability of the material must have good frequency response characteristics. Soft magnetic alloys are a class of materials with high permeability and are commonly used in the manufacture of magnetic cores, transformers, inductors, inductors, sensors, etc. in electromagnetic devices.
Low frequency magnetic field shielding low frequency magnetic field is more difficult to shield. The use of high permeability materials with high absorption loss to shield low frequency magnetic field is a common method of magnetic field shielding. The following points should be noted when using high magnetic permeability materials:
(1) Magnetic permeability decreases with increasing frequency, and the data given in the material manual is usually the permeability at DC. The higher the permeability at DC, the faster it decreases with increasing frequency.
(2) High permeability materials will experience a decrease in permeability after processing or after being subjected to shock or collision, so appropriate heat treatment must be applied after processing.
(3) Magnetic permeability is related to the strength of the applied magnetic field. When the applied magnetic field is moderate, the magnetic permeability is the highest; when the applied magnetic field is too strong, the shielding material will be saturated, and the field strength at magnetic saturation is related to the type and thickness of the material. When the magnetic field to be shielded is very strong, if the use of high permeability materials, will lose shielding effectiveness due to magnetic saturation; and the use of low permeability materials, due to insufficient absorption loss, will not meet the requirements. In this case, double-layer shielding can be used.
In practical applications, materials with high permeability should also have low hysteresis loss, low eddy current loss, and high saturation magnetic induction strength to ensure the performance and efficiency of electromagnetic devices.
