**1. Introduction**

In the induction heating processes, the main problem is to increase process efficiency, which can be achieved through the intervention of different parts of the installation [9,10,11]

A method used to increase electrical energy conversion efficiency, which is referred to in the literature and that also was considered in the study discussed in this paper is to use magnetic flux concentrator[1,2,6]. If we analyze the structure of hypothetical wound inductors, located close to a work piece, as shown in Figure 1, we can see that for this structure is equivalent electric circuit in Figure 2.

Ohm's Law applied to the magnetic circuit is:

$$NI = \mathbb{R}\_m \times \Phi\_i \tag{1}$$

The magnetic reluctance equivalent of the system consists of two parallel reluctance: magnetic reluctance of the work piece Rmp and the air gap magnetic reluctance between spiral inductors and piece of heated, Rma, in series with the magnetic reluctance of outside environment, Rme, of the inductor coils

If the magnetic reluctance of the piece, Rmp, depends on the material characteristics, and the air gap reluctance Rma can not be reduced below a value that depends on technological conditions of the heating process, remains the method of intervention to reduce the equivalent reluctance of the system, improving the environment reluctance outside coils inductors, Rme.

This is actually the role of magnetic field concentrator using in inductive heating processes.

To achieve these magnetic concentrators in practice it is using a variety of materials and could therefore be useful brief review of their focusing on magnetodielectric materials made and used in the study approached the work.

© 2012 Hoble and Silaghi , licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Requirements of magnetic materials in induction heating applications can be very severe in many cases[1,8]. They must operate within a broad category of frequencies, to possess permeability and high saturation flux densities, have stable mechanical properties and resistance to high temperatures caused by heat loss due to magnetic concentrators and heat transferred from the heated parts.

Magnetodielectric Materials – Use in Inductive Heating Process 81

**Figure 3.** B=f (H) curves [1;2,6]

different axes.

**2. Magnetodielectric materials** 

types of magnetodielectric materials [6].

These materials are composite materials made of magnetic particles and dielectric materials that serve as links and electrical insulators of magnetic particles. Magnetic properties of magnetodielectric materials (MDM), depend on constituent particle properties, their shape and volume. Mechanical and thermal characteristics depend mainly on the ratio of magnetic material, and dielectric material. The general properties of materials depend by manufacture technology, their achievement, given the fact that their production involves a pressing process, who making certain properties, especially magnetic to manifest differently on

The world leader in the manufacture of MDM is FLUXTROL Company, which made several

In those that follow will present the results of several studies made by the authors, to obtain

To achieve magnetodielectric material was used dielectric material, consisting of two components manufactured epoxipoliamidic resin without solvents, that drying to 80 C.

Mixing ratio of components A / B is 2/1 parts by weight. The product is used in electrical engineering, as mass of hardware, building and construction fill in some details of engines

a magnetodielectric material by using it in inductive heating processes.

**Figure 1.** Hypothetical structure of an inductor – work piece of heated

**Figure 2.** Equivalent electric scheme of Inductor - heated piece

Three groups of magnetic materials can be used to concentrate the magnetic flux: laminates, ferrites and magneto dielectric materials, so-called MDM materials.

Figure 3. present variation curves B = f (H), compared to laminated, ferrite materials and MDM [1,2,6], used in magnetic field concentrator construction.

**Figure 3.** B=f (H) curves [1;2,6]

80 Dielectric Material

transferred from the heated parts.

**Figure 1.** Hypothetical structure of an inductor – work piece of heated

**Figure 2.** Equivalent electric scheme of Inductor - heated piece

ferrites and magneto dielectric materials, so-called MDM materials.

MDM [1,2,6], used in magnetic field concentrator construction.

Three groups of magnetic materials can be used to concentrate the magnetic flux: laminates,

Figure 3. present variation curves B = f (H), compared to laminated, ferrite materials and

Requirements of magnetic materials in induction heating applications can be very severe in many cases[1,8]. They must operate within a broad category of frequencies, to possess permeability and high saturation flux densities, have stable mechanical properties and resistance to high temperatures caused by heat loss due to magnetic concentrators and heat
