Neodymium Disc Magnets Are Used In An Open Circuit

  •   The macroscopic inhomogeneity of the external magnetic field of the Ring Neodymium Magnet is closely related to the spatial distance and the shape design of the permanent magnet. Permanent magnet technology such as powder particles, degree of orientation, sintering and solidification, mechanical processing, etc. will affect the non-uniformity of the external magnetic field of the permanent magnet, such as magnetization deflection, symmetry, and smoothness. The main permanent magnets used in the market are cast permanent magnets, ferrite permanent magnets, rare earth permanent magnets and so on.

      Shape design, demagnetization, craftsmanship, etc., and there are basic laws in common. In this paper, taking anisotropic rectangular neodymium iron boron and samarium cobalt permanent magnets for synchrotron radiation undulators as examples, the theoretical analysis of various factors that affect the inhomogeneity of the external magnetic field of the permanent magnets is carried out, so as to provide high-precision permanent magnets for undulators and other high-precision permanent magnets. The physical design of the magnetic device and the development of high-uniform permanent magnets provide a certain reference basis.

      What is the non-uniformity of the external magnetic field?

      The inhomogeneity of the external magnetic field of a rectangular magnet generally refers to the uniformity and relative size of the area of the main magnetic field, the three-dimensional remanence distribution (magnetization deflection angle), the symmetry of the N/S pole space magnetic field, and the smoothness of the magnetic field. The uniformity of the good field area of the main magnetic field is generally expressed by the fluctuation of the magnetic field value B0 of the cross-sectional area in the orientation direction. The fluctuation value depends on the physical design and engineering development requirements of different permanent magnet devices, and the indicators are also different. The so-called "smoothness" of the external magnetic field of permanent magnets means that there is no large "sawtooth" magnetic field distribution.

      Under ideal uniform magnetization conditions, the distribution of the good field area of the main magnetization field Bz is closely related to the relative area size and the spatial distance. As the distance increases: (a) → (b) → (c) → (d), the central area The intensity of the main magnetic field Bz gradually decreases, and the area of the good field first increases and then decreases (the maximum in Figure 1(c)), while the main magnetic field Bz in the edge area decreases rapidly with the increase of distance. This phenomenon also indicates that under the same conditions Next, as the magnetic gap of the permanent magnet device decreases, the uniformity of the magnetic field has an optimized optimal magnetic gap value. This also shows that under the condition of a small gap magnetic circuit, if the magnetic field is to achieve high-quality requirements, the shape of the permanent magnet Design, magnetic field uniformity, permanent magnet device system design, etc. put forward higher requirements. The good field distribution of the permanent magnet's main magnetic field is closely related to the shape design of the permanent magnet. The molecular current method can be used to calculate the external magnetic field of the permanent magnet of any shape Spatial distribution pattern.

      Factors Affecting Inhomogeneous External Magnetic Field of Rectangular Neodymium Magnet

      Demagnetization field

      The demagnetizing field has a complex effect on the micro-inhomogeneity of the external magnetic field of the permanent magnet.

      In engineering, permanent magnets are used in an open circuit, and there is a demagnetizing field, which is one of the significant differences between permanent magnets and electromagnets. When the permanent magnet is magnetized under its action, the internal magnetic field is not equal to the external magnetic field. The size and distribution of the demagnetizing field are mainly determined by the geometry and size of the permanent magnet. When a demagnetizing field exists, even if it is magnetized in a uniform external magnetic field, since the magnetic field generated inside the permanent magnet is not uniform, the permanent magnet cannot be guaranteed in most cases. Absolutely uniform magnetization of the magnet. The theory proves that only ellipsoidal permanent magnets can meet the requirements of uniform magnetization.

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