Evaluation of the magnetization direction effects on ferrite PM brushless fractional machines

Permanent magnets are frequently adopted in small brushless machines for automotive applications. Normally anisotropic ferrites, but some research on bonded magnets is being carried on. Several types of magnetization can be proposed, involving different levels of complexity in the magnetization process. In the paper a comparison between parallel and radial magnetization is described, taking into account on one side the major complexity of the radial process and on the other the small power derating of the paralle

Innovative SMC Insulation Technique Applied to Axial Flux Machine Prototypes

The paper describes in detail the realization of an axial flux machine prototype adopting an innovative Soft Magnetic Composite (SMC) material. The novel technique here presented regards a Layer-by-Layer deposition adopted to insulate pure iron powder grains previously selected. The obtained material is then used to prepare the machine's stator parts. The activity steps are detailed: from the powder preparation to the molding phase, the consequent milling for the final shape, and the consequent magnetic, energetic and mechanical characterization. The prototype design and assembly imply the realization of the stator with the adopted innovative material, and the Authors also realized the preparation of the rotor equipped with bonded magnets. The preliminary experimental results are presented at the end, and considering the machine to be the first trial with the presented material, the efficiency of 77% should be viewed as a promising result for the future development of the activity

Rapid Characterization Method for SMC Materials for a Preliminary Selection

In electrical machines, laminated steels are commonly adopted as soft magnetic materials, while for permanent magnets, sintered ferrites and NdFeB are the most common solutions. On the other hand, the growing demand for volume reduction with the increment of efficiency leads to the necessity of exploring other magnetic materials able to face the challenge better than the traditional ones. Bonded magnets have been used to replace sintered magnets, obtaining a better use of space and particular magnetic properties. Instead, for the magnetic circuit, Soft Magnetic Composites (SMC) allow realizing very complex magnetic design (3D path for flux) with iron loss reduction at medium-high frequencies, especially for the eddy currents loss contribution. On the other hand, SMC materials have such drawbacks as low mechanical properties and high hysteresis losses. For this reason, in this work, different studies considering several variables have been carried out. SMCs were produced through a moulding process; inorganic and organic layers to cover ferromagnetic particles were used, adopting different coating processes. Particu-lar tests have been performed for a quicker and more indicative overview of the materials ob-tained. The single sheet tester (SST) is easier than traditional toroidal methods; on the other hand, the multiplicity of variables affects the SMC materials and their process. For this reason, coercivity and conductibility tests permit rapid measurement and provide a direct classification of the produced SMCs, providing the main information needed to select suitable materials. Re-sults highlighted that choosing the more appropriate SMC material is possible after using these simple preliminary tests. After these tests, it was possible to argue that with 0.2 wt% of phenolic resin as the organic layer (and compaction pressure of 800 MPa), it is possible to produce a good SMC. On the other hand, the SMC with 0.2 wt% of epoxy resin (and compaction pressure of 800 MPa) gives a minor coercivity value. Additionally, despite the SMC with the inorganic layer, 0.2 wt% of nano-ferrites showing the best coercivity values (specifically for vacuum treatment at 600 °C), their resistivity was unsatisfactory

Functional characterization of L-PBF produced FeSi2.9 Soft Magnetic Material

Additive manufacturing (AM) is a production technology attractive for various sectors such as aerospace, biomedical, and automotive. The advantages are various, including being able to create objects with complex geometry and through a careful study of topological optimization, reduce the weight while maintaining mechanical performance. The aim of the present work is to study the feasibility of producing ferromagnetic materials using AM technology for electrical application such as rotor for electrical machine or electromagnetic devices via Laser Powder Bed Fusion (L-PBF). L-PBF is shown to be effective to produce soft magnetic materials (SMMs) such as FeSi2.9. Dedicated test samples with various geometries have been manufactured for evaluating the electrical and magnetic performance under as-built conditions and after annealing

Innovative magnetic materials for the new applications in electrical machines

Permanent magnets play a key role as a component in a wide range of devices utilised by many industries; they are widely used in several electromechanical applications to convert energy, including actuators, motors and sensors, home appliances, office automation equipment, speakers, aerospace, wind generators and more. Traditionally the adopted PMs were obtained from Rare Earth components, such as NdFeB, with high magnetic performance, but expensive. The research of alternative permanent magnets, in many cases has brought to choose the ferrites, mainly due to their low cost, but sometimes with significant design modifications of the final circuit, and possible increment of the weight. Permanent magnets can roughly be divided into two categories: sintered (metallic) and bonded, these last representing a valid alternative to the first. Bonded magnets consist of two components: a hard magnetic powder and a non-magnetic binder; the powder may be hard ferrite, NdFeB, SmCo, and is mixed with binders for compression or injection moulding. The benefits lie in the adoption of polymeric binders to prepare the magnetic mixture: the resulting magnetic characteristic can be then “tuned” by adopting different percentages of the plastic binder. Moreover, the realisation process is simpler and cheaper than that of sintered materials, and no special protective treatment is needed. The majority of the magnetic circuits are made with soft magnetic materials. Commonly laminated steels are adopted but recently the use of Soft Magnetic Composite (SMC) materials has increased representing a new solution to design the electrical machines with respect to traditional electrical steels. SMC materials are realized with pure Iron grains coated and insulated by means of a layer that should be organic or inorganic. With respect to traditional laminated steel, these materials present different advantages: the capability to lead the magnetic flux in all directions, the volume reduction, the possibility to realize components with new complex shapes and geometries, and the reduction of iron losses, mainly the eddy currents, at medium and high frequency. On the other hand, the mechanical performances, in terms of strength, are in general weak. Furthermore, a new material typology is introduced: the Hybrid Magnetic Composites (HMC), which are obtained with a combination of soft and hard magnetic materials mixed with a binder. The basic idea is that such materials should reflect the performance of AlNiCo magnets, low coercivity and adequate remanence, typically used in sensors applications. Prototypes of traditional and unconventional rotating machines, such as assisted reluctance motors, brushless DC motors, axial flux machines and electromechanical frequency converters, have been studied in own laboratories and tested to evaluate the results coming from the adoption of the proposed materials in substitution of the commonly adopted (and expensive) Rare Earth sintered magnets. Different type of electrical machines can adopt innovative magnetic materials with the aim to improve their performance. Induction motors are very useful and robust machines; on the other hand, such type of machines does not have a high dynamic behaviour. The DC motors can be easily controlled, but the presence of the brushes causes limitations on the efficiency, thermal restrictions and reduced life. The axial flux motors (AFM) have high efficiencies but the construction of the machines is very complex. The synchronous reluctance machines (SRM) have a lower cost compared to brushless ones. In general, the reluctance electrical machines don’t use permanent magnets. In this way, they have a reduction in the costs and allow a high overload capability. On the other hand, the lower power factor and power density, compared to PM synchronous motor (PMSM), are the main disadvantages. The filling of flux barriers with the permanent magnets allows the overcoming of these drawbacks. However, the regular ferrite and NdFeB sintered magnets cannot fill the flux barriers with complex geometries. For this reason, the use of bonded magnets can be a solution for a better utilization and design of flux barriers. Therefore different prototypes have been prepared and analyzed in our laboratories using SMC materials. Several experiments have been performed using dedicated test benches, where magnetic, energetic and mechanical aspects have been considered. On the other hand, with regard to HMCs, various magnets have been made in our laboratories, and different properties have been investigated: the effect of Iron content in the material and, also the binder content effect has been analysed

Innovative magnetic materials for the new applications in electrical machines

Permanent magnets play a key role as a component in a wide range of devices utilised by many industries; they are widely used in several electromechanical applications to convert energy, including actuators, motors and sensors, home appliances, office automation equipment, speakers, aerospace, wind generators and more. Traditionally the adopted PMs were obtained from Rare Earth components, such as NdFeB, with high magnetic performance, but expensive. The research of alternative permanent magnets, in many cases has brought to choose the ferrites, mainly due to their low cost, but sometimes with significant design modifications of the final circuit, and possible increment of the weight. Permanent magnets can roughly be divided into two categories: sintered (metallic) and bonded, these last representing a valid alternative to the first. Bonded magnets consist of two components: a hard magnetic powder and a non-magnetic binder; the powder may be hard ferrite, NdFeB, SmCo, and is mixed with binders for compression or injection moulding. The benefits lie in the adoption of polymeric binders to prepare the magnetic mixture: the resulting magnetic characteristic can be then “tuned” by adopting different percentages of the plastic binder. Moreover, the realisation process is simpler and cheaper than that of sintered materials, and no special protective treatment is needed. The majority of the magnetic circuits are made with soft magnetic materials. Commonly laminated steels are adopted but recently the use of Soft Magnetic Composite (SMC) materials has increased representing a new solution to design the electrical machines with respect to traditional electrical steels. SMC materials are realized with pure Iron grains coated and insulated by means of a layer that should be organic or inorganic. With respect to traditional laminated steel, these materials present different advantages: the capability to lead the magnetic flux in all directions, the volume reduction, the possibility to realize components with new complex shapes and geometries, and the reduction of iron losses, mainly the eddy currents, at medium and high frequency. On the other hand, the mechanical performances, in terms of strength, are in general weak. Furthermore, a new material typology is introduced: the Hybrid Magnetic Composites (HMC), which are obtained with a combination of soft and hard magnetic materials mixed with a binder. The basic idea is that such materials should reflect the performance of AlNiCo magnets, low coercivity and adequate remanence, typically used in sensors applications. Prototypes of traditional and unconventional rotating machines, such as assisted reluctance motors, brushless DC motors, axial flux machines and electromechanical frequency converters, have been studied in own laboratories and tested to evaluate the results coming from the adoption of the proposed materials in substitution of the commonly adopted (and expensive) Rare Earth sintered magnets. Different type of electrical machines can adopt innovative magnetic materials with the aim to improve their performance. Induction motors are very useful and robust machines; on the other hand, such type of machines does not have a high dynamic behaviour. The DC motors can be easily controlled, but the presence of the brushes causes limitations on the efficiency, thermal restrictions and reduced life. The axial flux motors (AFM) have high efficiencies but the construction of the machines is very complex. The synchronous reluctance machines (SRM) have a lower cost compared to brushless ones. In general, the reluctance electrical machines don’t use permanent magnets. In this way, they have a reduction in the costs and allow a high overload capability. On the other hand, the lower power factor and power density, compared to PM synchronous motor (PMSM), are the main disadvantages. The filling of flux barriers with the permanent magnets allows the overcoming of these drawbacks. However, the regular ferrite and NdFeB sintered magnets cannot fill the flux barriers with complex geometries. For this reason, the use of bonded magnets can be a solution for a better utilization and design of flux barriers. Therefore different prototypes have been prepared and analyzed in our laboratories using SMC materials. Several experiments have been performed using dedicated test benches, where magnetic, energetic and mechanical aspects have been considered. On the other hand, with regard to HMCs, various magnets have been made in our laboratories, and different properties have been investigated: the effect of Iron content in the material and, also the binder content effect has been analysed

A Novel Thermographic Method and Its Improvement to Evaluate Defects in Laminated and Soft Magnetic Composites Devices

Electromagnetic devices may be affected by the presence of local losses due to material defects or magnetic anomalies caused by mechanical processing. The localization of such defects is the main goal of this article; a noninvasive method has been pursued to perform the inspection and detection of imperfections or defects. The adopted approach is based on the observation of the device under test with a high-speed IR camera; no limitations in size and shapes devices are considered and the method can be widely adopted. Examples of defects detection in the magnetic circuit realization are proposed, both for traditional ferromagnetic laminated sheets and for soft magnetic composites

Novel method for evaluating the iron losses in SMC materials

Industrial 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

The Magnetization Effect on Soft Magnetic Composite Prepared Stators of Axial Flux Motors

The axial flux motors should represent a good and reliable solution for a large variety of applications. The use of soft magnetic composite materials allows to resolve some drawbacks of the aforementioned motors. Two axial flux motors have been prepared with the same design. The unique difference consists of soft magnetic composite stator preparation. The magnetization effect during the stators production process has been evaluated. Different tests have been performed in order to compare a magnetized and a not magnetized stator. Distinct differences have been noted, showing some advantages for the prototype with aligned SM C material