Rapid Characterization Method for SMC Materials for a Preliminary Selection

Emir Pošković,Marco Actis Grande,Fausto Franchini,Luca Ferraris,Federico Carosio

doi:10.3390/app112412133

Abstract

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. Particular tests have been performed for a quicker and more indicative overview of the materials obtained. 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. Results 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.

Highlights

IntroductionMagnetic materials have been adopted in several sectors, from industrial, services, and IT to households, and in many applications and devices are the principal parts or components
The pressure level increment has a high impact on the magnetic and mechanical because the higher resistivity loss already occurs for lower pressures
The traditional toroidal magnetic test is the main standard for Soft Magnetic Composites (SMC) materials but requires a long time due to the manufacturing and winding process

Summary

Introduction

Magnetic materials have been adopted in several sectors, from industrial, services, and IT to households, and in many applications and devices are the principal parts or components. In the case of hard magnetic materials, the general use concerns the flux generators and magnetic coupling; soft materials are adopted in the magnetic core of electrical motors and transformers [1,2,3]. The main properties depend on the type of magnetic materials. The remanence (Br), the maximum magnetic energy density (BHmax) and the coercivity (Hc) represent the principal information

Methods

Results

Conclusion