New Soft Magnetic Composites for electromagnetic applications with improved mechanical properties

Abstract

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.

Effect of Granulometry and Oxygen Content on SMC Magnetic Properties

“…The following powders have been chosen: Powder A (average grain value: 45 μm and oxygen content 0.5% in weight), Powder B (average grain value: 150 μm and oxygen content 0.06 wt %) and Powder C (average grain value: 425 μm and oxygen content 0.25 wt %). In this research a phenolic resin, already adopted in previous works [21], [25] has been used. Iron powders have been admixed with 0.2% wt of the resin.…”

“…Samples obtained were undergoing the same characterization as the resin added materials. The magnetic characterization was performed at room temperature through a magnetic toroidal test [21], [25], [26]. The measuring system provides a controlled sinusoidal voltage waveform with very low harmonic distortion, without an excessive sample heating -even at high amplitudes -avoiding the need of an additional cooling system.…”

“…In this way, some simplifications in the process activities can be operated with respect to the same machines realized with magnetic sheets. Several researches have been carried out by the Authors on the aforementioned materials, with promising results both in terms of magnetic and mechanical properties [19]- [21]. The effect of chemistry and processing parameters on the performances of SMC materials have been evaluated in [22]- [24].…”

“…Three iron powders with different grain sizes and different oxygen contents have been evaluated as starting materials for the production of Soft Magnetic Composite. All powders have been added to 0.2% wt of polymeric phenolic binder to act as insulating layer [21]. The layer is namely covering every single grain and performs the action of electrical insulation and mechanical strength between particles.…”

Dynamics of the line-start reluctance motor with rotor made of SMC material

“…For several years the use of SMC materials, as a part of electric motors, was tested [9][10][11][12][13]. The main reason of these tests is the core loss reduction, which is especially important for motors energized by sources generating waveforms with the frequency greater than 50 Hz (e.g.…”