Soft Magnetic Composite Materials AC Properties and their Application in Electrical Machines

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Eddy current losses in alternating current electromagnetic applications are ruled by resistivity. The traditional solution is to use stacks of electro-steel sheets, which effectively break the induced current paths. However the lamination technique is normally applied in 2D-designs and in addition can become more costly and complex as the frequency of the application increases. Soft Magnetic Composites, SMC, are isotropic, have improved high frequency performance and can be compacted to 3D-shapes using the established powder metallurgy process. Excellent dimensional accuracy, smooth surfaces and flexibility in component design opens new dimensions for creating innovative 3D machine concepts. SMC-materials are basically pure iron powder particles coated with a very thin, electrically insulating layer. A range of Somaloy® products are available today and the range is being extended. An SMC material is defined, not only by the base powder, but also additive(s) selected and the processing route chosen. This allows tailoring of properties for specific application requirements. An overview of available SMC materials and properties achievable will be given. Thanks to SMC materials high resistivity and ability to carry flux in three dimensions complex flux paths in machine types such as transverse flux motors can effectively be produced on an industrial scale. Larger structures can be realized by dividing the core into segments. Joining is easily managed thanks to the possibility to integrate assembly features on SMC components. 3D flux path enables deeper and more efficient flux concentration. A low air gap flux density in e.g. a radial flux machine can be concentrated into the tooth body in the circumferential as well as the axial direction. This minimizes the winding turn length required. Flux can furthermore be distributed in the same directions in the core back realizing a radialy thinner core back, thus reducing the diameter of the machine. If the new design opportunities are carefully implemented, SMC-motors can successfully compete with lamination-motors even at grid frequencies. Recent progress in applications will be described as well as some examples of commercial products presented.

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Soft magnetic composites (SMCs) are a class of magnetic materials that have the potential to create lighter and more efficient electronic devices. SMCs provide high electrical resistivity while providing high magnetic permeability, consisting of a magnetically conductive core and an insulating coating traditionally made via powder metallurgy. Until recent advances, devices needing materials with these magnetic properties have been made by complex and geometrically limited laminations or press and sinter methods; both possessing issues. This paper establishes that a multi-material system incorporating NiZnCu-ferrite and high purity iron processed via additive manufacturing (AM) can serve as a manufacturing route for SMCs, with as-built samples showing high maximum relative permeability (~ 200,000). The results demonstrate the viability of laser powder bed fusion (L-PBF) AM to produce SMCs with higher permeability than press and sinter SMCs utilizing the same powder system and chemistry while also indicating new challenges that must be overcome to produce a fully dense SMC via additive manufacturing.Graphic abstract
The integrated starter generator used in micro hybrid electric vehicle is usually claw pole motor. The claw pole core in the motor is forged by low carbon steel, which is of complex technology and the eddy current loss of the whole conductor in the magnetic field is large. In order to solve these problems, a novel claw pole motor is proposed in this paper, which uses iron-based soft magnetic composites to prepare claw pole core and insert permanent magnet between claw poles. By studying the preparation process parameters of iron-based soft magnetic composites, it is found that the mechanical properties and magnetic properties of the soft magnetic composites are the best under 700 MPa pressing pressure and 500°C annealing temperature. A prototype is designed and manufactured, and its power generation and starting performance are tested, which can meet the performance requirements of 48V micro hybrid system.
Ferromagnetic powder particles coated with electrical insulating inorganic layers constitute composite materials used as powdered iron cores in electromagnetic applications. The aforementioned surface layers of these soft magnetic composites (SMC) are responsible for their high electrical resistivity. The perseverance of the coating through annealing processing step is crucial to the performance of finalized SMC products. In the present study, the thermal stability and microstructure of an iron phosphate based surface layer from a commercially available SMC powder were investigated by coupling various analytical techniques. The material was annealed at different temperature regimes, both in oxidizing (air) and inert (N2) conditions in order to isolate the effect of temperature from the atmosphere composition on the chemical state of the coating. X-ray photoelectron spectroscopy (XPS) was utilized to assess the composition of the surface layer at all conditions. Moreover, phosphate-based chemical standards were processed and analyzed in a similar manner so as to facilitate the interpretation of the observed XPS spectra from the SMC powder. High resolution scanning electron microscopy, energy-dispersive X-ray spectrometry and X-ray diffraction were implemented in order to fully characterize the material under question. The results indicated the transition of the insulating layer from an amorphous state to fully crystalline under annealing in inert atmospheric conditions. Moreover, it was observed that phosphates are still present in the coating in mixture of valance states. Conversely, a thick iron oxide scale was formed under treatment in air, and no phosphorus signal was detected, indicating a total decomposition of the layer. Copyright © 2016 John Wiley & Sons, Ltd.
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A surfaced permanent magnet spherical motor is capable of operating as three degree of freedom that used for the joints of the robot's arm, leg, and eyes. Ongoing research like new concept is essential part of motor field, it will make a great contribution in the future the overall portion of the motor, is becoming expected. The author analysis torque characteristics in spherical motor with state of rotating and positioning. And future design direction is smaller motors with equivalent or higher output. Solutions as torque and efficiency improvements are selecting the core with special processing type like powder metallurgy materials. Their special characteristic is high permeability and low eddy current losses at high speed, so improved the torque and efficiency.
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