685 research outputs found
O Araguaia pelos Militares: Imaginários e Barbáries
No full textReview text “Araguaia by the Military: Imaginary and Barbaries” (2008), by the author Flávia M. Franchini Ribeiro.Review text “Araguaia by the Military: Imaginary and Barbaries” (2008), by the author Flávia M. Franchini Ribeiro.Texto da resenha "O Araguaia pelos Militares: Imaginários e Barbáries " da autora Flávia M. Franchini Ribeiro
Hybrid magnetic composite (HMC) materials for sensor applications
No full textSeveral applications adopt electromagnetic sensors, that base their principle on the presence of magnets realized with specific magnetic materials that show a rather high remanence, but low coercivity. This work concerns the production, analysis and characterization of hybrid composite materials, with the use of metal powders, which aim to reach those specific properties. In order to obtain the best coercivity and remanence characteristics various "recipes" have been used with different percentages of soft and hard magnetic materials, bonded together by a plastic binder. The goal was to find out the interdependence between the magnetic powder composition and the characteristics of the final material. Soft magnetic material (special Fe powder) has been used to obtain a low coercivity value, while hard materials were primarily used for maintaining a good induction remanence; by increasing the soft proportion a higher magnetic permeability has been also obtained. All the selected materials have been characterized and then tested; in order to verify the validity of the proposed materials two practical tests have been performed. Special magnets have been realized for a comparison with original ones (AlNiCo and ferrite) for two experimental cases: the first is consisting in an encoder realized through a toothed wheel, the second regards the special system used for the electric guitars
A thermographic method for the evaluation of the iron losses distribution in electromagnetic devices
No full textThe Authors operate in the field regarding the development and realization of small electromagnetic and electromechanical devices, and the study of the required magnetic materials; for that purpose the availability of a method for evaluating with discrete accuracy the distribution of the iron losses in such devices should be very useful. At that aim a methodology is here proposed based on the use of a particular thermographic analysis; a special series of tests have been performed for obtaining the distribution of the iron losses inside the magnetic circuit. In this paper the method application has been carried out for the case of a small transformer. The results are encouraging and allow to think to apply the procedure for other devices and materials, such as for example, components realized with Soft Magnetic Materials (SMC)
New Soft Magnetic Composites for electromagnetic applications with improved mechanical properties
No full textThe chance to move from 2D to 3D approach in the design of the electrical machines is made possible by the availability of Soft Magnetic Composites (SMC), iron based powders, insulated and pressed to realize shapes otherwise impossible with the traditional lamination sheets technology. Some commercial products are available on the market as “ready to press” powders, which presents good magnetic and energetic properties but are sometimes weak under the mechanical point of view; other products aim at improving this aspect but with considerable process complications and relative cost. The experience of the Authors in the realization of bonded magnets with the adoption of selected organic resins has been partly transferred in the research field of the SMC in order to investigate the possibility to obtain good mechanical properties maintaining the magnetic characteristics of the Insulated Iron Powder Compounds (I.I.P.C.) taken as reference. The paper presents the activity that has been carried out in the realization of SMC mixing iron powders and phenolic resin, in different weight percentages and mold pressures. The obtained results are considered satisfactory under the point of view of the compromise between magnetic and mechanical properties, considering also that the required productive process is simpler. The comparison of the obtained results with those related to commercial products encourages to carry on the research, also because of the reduced cost of the proposed SMC at parity (or better) performance
Design optimization of bonded PM BLDC motors with reference to the cogging torque amplitude
No full textDefects detection in laminated and soft magnetic composites devices with a novel thermographic method
No full textThe realization of electromagnetic devices may implies the presence of local losses caused by material defects or by magnetic anomalies caused by mechanical processing. The problem of such defects location is the object of the present work; the aim of obtaining information about imperfections or defects with a non invasive inspection has been pursued. The adopted approach is based on the observation of the device under test with a particular thermographic camera; no limitations in size and shapes devices are considered and the method can be widely adopted. Examples of defects in the magnetic circuit realization are described, both for traditional ferromagnetic laminated sheets and for Soft Magnetic Composite
Novel method for evaluating the iron losses in SMC materials
No full textIndustrial systems comprehending reduced losses components are always more and more requested: the Standards push towards the improvement of the efficiency, and this forces to find new solutions to fulfill the constraints. For laminated steels appropriate methods to measure or estimate the iron losses are applied: Epstein frame or Single Sheet Tester (SST) for measurements, FEM simulation and analytical approach to estimate the penetration of the losses due to mechanical processing. In the case of the Soft Magnetic Composites (SMC) the test method normally adopted is the one with toroidal samples, which cannot give information about the losses distribution and the contribution due to processing. For this reason a new method based on a thermographic analysis is proposed: a contactless and non-destructive technique to evaluate the core losses and their distribution has been developed. The principle is based on the observation of the temperature changes distribution on the device surface; a deep elaboration of the temperature information allows to deduce the specific iron losses distribution. In this way it is possible to analyze in details the energetic behavior of the SMC and also to evaluate the impact of some process parameters (molding pressure, orientation etc.) on the losses; moreover the method could be applied to devices of every shape and dimension and adopted also outside the laboratories facilities
Study of the Halbach magnetization in small PM electrical machines adopting the bonded magnets
No full textIn the recent past the authors dedicated much work to small PM motor adopting permanent bonded magnets, and to the magnetization problems. Now it is largely proposed the so-called Halbach magnetization, presenting the directions of the magnetic induction variable along the magnet; its constitutes a tentative of sinusoidality for the magnetic induction component orthogonal to the magnet surface. It was decided to try to realize a motor prototype through the realization of the magnets by accosting small sectors, each with a magnetization direction different, and aiming to obtain an Halbach magnetization. In this paper a FEM simulation activity is presented to select the proper choice of the number and characteristics of the elementary sectors. At first the simulation instrument reliability has been tested through a confrontation between simulated and experimental results for some typical situations. Then the analysis was devoted to compare the windings rms voltage value and the cogging torque amplitude; the selected reference case is the one providing a radial magnetization. The analyzed solutions provide some hypothetical composed magnets, having different number of sectors and different angular amplitudes. Such activity allowed interesting considerations and a criterion useful for the choice of the magnets characteristics and for the number of the elementary sectors to be adopted for the motor prototype. The negative effect of the Halbach solution on the cogging torque amplitude is considered too
Effect of the Insulating Layer on the Properties of SMC Inductors
No full textIn inductor applications, different soft magnetic materials are used depending on the frequency range. Owing to powder metallurgy technology and to the increase in the implementation of innovative multifunctional materials, it is possible to find an alternative to the traditional magnetic materials of the inductance application sector. This study concerns a deep analysis related to soft magnetic composite materials. The insulating layer’s effect is investigated to explore the applicability of such materials to the inductor sector. Four coatings systems are selected and two types of samples are prepared in the shape of a toroid and a rod, which are tested in different operating conditions. The rod inductors are also compared with a traditional one, based on soft ferrite materials. This work aims to integrate data coming from different measuring devices: the useful small-signal measurements of an RLC meter are completed by large-cycle data measured through a hysteresigraph. Different parameters are considered for the investigation: magnetic permeability (maximum and initial), iron losses at different induction peak values, and inductor quality factor are the most important. The obtained results prove that each analysis type is not fully reliable without the other in determining the coatings’ effects on the SMC inductors’ performance. In the end, it is demonstrated that SMC inductances can be successfully applied in a particular frequency range
- …
