Autor/autori: Constantin D. STĂNESCU, Liliana CĂINICEANU

Abstract: Crowded permanent magnets of NdFeB -type have the superior properties to those intered as shown by the magnetic circuit modeling using finite element method (FEM). Determination of the optimum material for magnetic circuit of high power audio devices is a complex problem. A very eficiente method, based on the value of the main functional properties, such as technological and material cost analysis method of optimum values developed by Prof. Univ.Emerit Dr. ing. Constantin D. Stanescu. Analysis method of optimum values for material properties present two models: statistical and analytic model . Magnetic materials for permanent magnets of NdFeB-type have superior properties compared to magnetic materials from barium ferrite. In the statistical model, analytical model and results from the experimental data and the importance of ferromagnetic material used for reinforcement, Armco iron magnetic properties with superior steel S235.Using sintered NdFeB permanent magnets instead of crowded NdFeB permanent magnets follows:-the less magnetic induction in the air gap ; -the losses of the magnetic circuit and the extremities of the air gap are greater than in the case of crowded NdFeB permanent magnets, because the sintered magnets require a different configuration of the magnetic circuit. Modeling of magnetic circuit of high power audio device was realized with the finite elements method (FEM) software package ANSYS. It is very important the geometric configuration of the circuit and the optimal choice of materials. Using the same materials, change the shape of the magnetic circuit geometry leads to increased air flow and the losses of magnetic flux are reduced totally . Changing the magnets of barium ferrite, respectively with sintered or crowded NdFeB permanent magnets, the performances of the magnetic circuit grow significantly. The maximum value of magnetic induction in the air gap magnetic circuit in ideal conditions was determined 1 136T. By changing the geometric configuration of permanent magnets, maximum value of magnetic induction can be reached at 1, 248T, with about 10% higher than the magnetic reference circuit. Magnetic flux leakage are larger in the magnetic circuit if the magnetic permeability of soft magnetic materials is reduced. The saturation magnetic induction is lower. It is very important that the construction of magnetic circuits to be used with high magnetic permeability materials to prevent their saturation

Keywords: Air gap, permanent magnets, magnetic flux