Abstract
In the field of electrical machines, the actual research activities mainly focus on improving the energetic aspects; for this reason, new magnetic materials are currently investigated and proposed, supporting the design and production of magnetic cores. The innovative aspects are related to both hard and soft magnetic materials. In the case of permanent magnets, the use of NdFeB bonded magnets represents a good solution in place of ferrites. For what concerns the soft magnetic materials, the adoption of Soft Magnetic Composites (SMCs) cores permits significant advantages compared to the laminated sheets, such as complex geometries and reduced eddy currents losses. SMC materials are ferromagnetic grains covered with an insulating layer that can be of an organic or inorganic type. The proposed study focuses on the impact of the particle size and distribution on the final material properties. The original powder was cut into three different fractions, and different combinations have been prepared, varying the fractions percentages. The magnetic and energetic properties have been evaluated in different frequency ranges, thus ranking the best combinations. The best specimens were then tested to evaluate the mechanical performances. The preliminary results are promising, but deeper analysis and tests are required to refine the selection and evaluate the improvements against the original composition taken as a reference.
Highlights
Magnetic materials play an essential role in several industrial applications, such as electromechanical devices, electronic, automotive, energy production, refrigeration, magnetic separators, household equipment, etc
Soft Magnetic Composites (SMCs) present further advantages compared to laminated steels: low eddy currents, low specific losses at medium-high frequencies and more compacted machine geometries; higher power densities for the same dimension compared to the traditional radial flux machines (RFM) are possible
The iron losses in SMCs can be divided into three components: the more common hysteresis and eddy currents losses and the last introduced excess losses,43,44 the latter being negligible in laminated steels and bulk/massive ferromagnetic materials
Summary
Magnetic materials play an essential role in several industrial applications, such as electromechanical devices, electronic, automotive, energy production, refrigeration, magnetic separators, household equipment, etc. Most of the cited applications are based on the use of electrical machines, which are principally made with soft and hard magnetic materials. Different magnetic materials, both soft and hard, have been studied and proposed to substitute the traditional ones.. Scitation.org/journal/adv replace them, such as the Soft Magnetic Composites (SMC).20–22 Such magnetic materials are made with a ferromagnetic base powder, whose particles are covered with an electrically insulating layer to limit the energy dissipation due to eddy current losses. SMCs present further advantages compared to laminated steels: low eddy currents, low specific losses at medium-high frequencies and more compacted machine geometries; higher power densities for the same dimension compared to the traditional radial flux machines (RFM) are possible.. Other promising materials are the so-called Hybrid Magnetic Composites (HMC), consisting of both soft and hard magnetic materials powders mixed, in which the mechanical solidity is given by a polymeric binder. HMCs are particular permanent magnets with very low coercivity and can be used in substitution of AlNiCo36 and ferrite magnets mostly in sensor applications.
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