During the past 50 years, the aim to reduce the eddy current losses in magnetic cores to a minimum led to the formulation of new materials starting from electrically insulated iron powders, today called Soft Magnetic Composites (SMC). Nowadays, this promising branch of materials is still held back by the mandatory tradeoff between energetic, electrical, magnetic, and mechanical performances. In most cases, the research activity focuses on the deposition of an insulating/binding layer, being one of the critical points in optimizing the final composite. This insulation usually is achieved by either inorganic or organic layer constituents. The main difference is the temperature limit since most inorganic materials typically withstand higher treatment temperatures. As a result, the literature shows many materials and process approaches, each one designed to meet a specific application. The present work summarizes the recent advances in state of the art, analyzing the relationship among material compositions and magnetic and mechanical properties. Each coating shows its own processing sets, which vary from simple mechanical mixing to advanced chemical methods to metallurgical treatments. From state of the art, Aluminum coatings are characterized by higher current losses and low mechanical properties. In contrast, higher mechanical properties are obtained by adopting Silicon coatings. The phosphates coatings show the best-balanced overall properties. Each coating type was thoroughly investigated and then compared with the literature background highlighting. The present paper thus represents a critical overview of the topic that could serve as a starting point for the design and development of new and high-performing coating solutions for SMCs. However, global research activity continuously refines the recipes, introducing new layer materials. The following steps and advances will determine whetherthese materials breakthrough in the market.

This paper aims to tackle the general problem of increasing the performances of small permanent-magnet (PM) machines, through the use of bonded magnets instead of the more diffused ferrite magnets. In particular, the study is developed for a fractional-slot concentrated winding PM machines for automotive applications. Neodymium bonded magnets with different and unconventional resins are realized in the internal laboratories. The rotors with the different magnet technologies are experimentally characterized, and the experimental values are compared with the simulation ones. The obtained results allow to define the possible performance increment. Finally, this paper analyzes the possible improvement of the rotor magnetic circuit for a better exploitation of the bonded magnets, without altering the stator structure and the motor housing.

The 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.

A new technology may be proposed for the realization of the magnetic parts of electromechanical devices, mainly for small electric machines. Such a technology provides the substitution of the traditional magnetic sheets with parts obtained by molding special magnetic powders [soft magnetic composites (SMC)]. The advantages may be constituted not only by economical reasons, but mostly by the possibility to realize parts having shapes otherwise impossible with the traditional lamination. Some commercial products are available in the market as “ready to press” powders, but their mechanical properties are in general not sufficient. To investigate the possibility to obtain good mechanical properties maintaining the magnetic characteristics of a selected commercial insulated iron powder compound, the authors have conducted a research activity based on the use of special iron powders and a selected epoxy resin as binder. The paper describes the activity carried out for the realization of SMC by mixing iron powders and Epoxy resin with different binder percentages and molding pressures. The obtained results have to be considered very satisfactory and suggest to continue the research argument to explore the possibilities of further improvements.

This study aims to produce Fe2.9wt.%Si ferromagnetic material via laser powder bed fusion (L-PBF) for the realization of electromagnetic actuators (EMA). This study is necessary as there are no documents in scientific literature regarding the manufacturing of Iron-Silicon plungers using the L-PBF additive manufacturing (AM) technique. The microstructure, and magnetic properties were characterized using various techniques. The results indicate that the samples produced via L-PBF process exhibit good magnetic properties (μ = 748, H_C = 87.7[ A/m ]) especially after annealing treatment at 1200° C for 1h (μ = 3224, H_C = 69.1[ A/m ]), making it a promising material for use in electromagnetic actuators.

In PM machines with curve shaped magnets the magnetization can have parallel or radial direction. The paper aims to evaluate the impact on the motor characteristics of magnetization direction, by means of simulation and experimental results. The proposed analysis is based on two different magnets technologies: one technology is industrially well established (anisotropic ferrite), while the other one is unconventional (rare-earth powder with phenolic resin bonded magnets). The case study is based on fractional horse power motor for electro-fan automotive applications: a concentrated windings fractional slots PM machine with external rotor.