M. Laudaa*, J. Füzera, P. Kollára, M. Strečkováb, R. Burešb

aInstitute of Physics, Faculty of Science, P.J. Šafárik Univesity, Park Angelinum 9, 04154 Košice, Slovakia

bInstitute of Materials Research, Slovak Academy of Science, Watsonova 47, 04001, Košice, Slovakia

CONCLUSION

The iron powder (ASC 100.29, Höganäs) with the size fraction in the range from

45 µm to 200 µm, was used as a base ferromagnetic material for a preparation of

soft magnetic composites. The phenol-formaldehyde resin modified by boron

PFRB was used as an electroinsulating layer. The iron particles covered by the

synthesized resin were compacted at 800 MPa to the ring samples for magnetic

measurements. The prepared samples were cured under the ambient pressure

up to 200 °C, which was suggested according to thermal degradation of the

modified resin.

The ring samples were used for magnetic measurements. Specific electrical

resistivity was measured by four-contact method adapted to ring-shaped

samples.

The AC hysteresis loops, were measured at frequency range from 2800 Hz to

22000 Hz, at maximum induction 0.1T, by a MATS-2010SA hysteresisgraph.

Total losses were calculated directly from the measured hysteresis loops.

We prepared two samples with different heights. As the base material was used

iron powder, covered by the phenol-formaldehyde resin modified by boron

(PFRB). We have measured total loss and than made a loss separation.

Hysteresis loss Wh was calculated directly from dc hysteresis loops. Intra eddy

current Wedintra and inter eddy current Wed

inter losses were calculated from known

formula. Excess loss Wexc was calculated by subtracting the hysteresis and eddy

current losses from total losses. The sample with higher height exhibit higher

total losses, because of higher hysteresis, inter eddy current and excess losses. Acknowledgement

This work was realized within the frame of the projects, ITMS 2622012001, ITMS 26220220105, which are supported by the Operational Program “Research and Development” financed through European Regional Development Fund. This work was also supported by the

Slovak Research and Development Agency under the contract No. APVV-0222-10 MAGCOMP and by the Scientific Grant Agency of the Ministry of Education of Slovak Republic and the Slovak Academy of Sciences, projects No. 1/0862/12 and No. 1/0862/12 and Internal

Research Grant System of Faculty of Science of Pavol Jozef Šafárik University in Košice VVGS-2013-107.

RESULTS

Fig.1. SEM image displaying the

microstructure of the fractured

surface of the sample.

Fig. 3. Loss separation per unit volume

as a function of frequency for sample 1

(Fe+PFRB, h = 1,68mm), measured at

maximum induction 0.1T in the frequency

range from 2800Hz to 22000Hz.. The

hysteresis Wh, intra eddy current Wedintra,

inter eddy current Wedinter, and excess

Wexc loss components involved in loss

separation are indicated.

Soft magnetic composites (SMCs), which are used in electromagnetic

applications, can be described as ferromagnetic powder particles surrounded by

an electrical insulating film. These composite materials offer several advantages

over traditional laminated steel cores such as reduction in weight and size. They

have some unique properties include three-dimensional isotropic ferromagnetic

behaviour, very low eddy current loss, relatively low total core loss at medium

and high frequencies, high electrical resistivity and good relative permeability.

MOTIVATION

The microstructure and morphology of the samples were examined by the

scanning electron microscope SEM (JEOL JSM-7000F). The iron powder (ASC

100.29) covered by PFRB resin has a high tendency to hold together in a very

tight arrangement without any significant porosity (Fig.1.). The PFRB polymer

melts during the heat treatment and consequently, it completely fills empty space

between iron particles (Fig.2.).

Fig.2. SEM images displaying

the macrostructure of the fractured

surface of the prism-shaped sample.

EXPERIMENTAL

Institute of Materials

Research

0 5000 10000 15000 20000 25000

25

30

35

40

45

50

To

tal lo

sse

s W

(J/m

3)

Frequency f ( Hz )

Whyst

Wed

intra

Wed

inter

Wexc

Sample 1 ( h = 1,68mm)

0 5000 10000 15000 20000 25000

25

30

35

40

45

50

To

tal lo

sse

s W

(J/m

3)

Frequency f ( Hz )

Whyst

Wed

intra

Wed

inter

Wexc

Sample 2 ( h = 3,53mm )

0 5000 10000 15000 20000 25000

30

35

40

45

50

To

tal lo

sse

s W

( J

/m3)

Frequency f ( Hz )

Sample 1, h = 1,68mm

Sample 2, h = 3,53mm

0 5000 10000 15000 20000 25000

0,0

0,5

1,0

1,5

2,0

2,5

Inte

r e

dd

y c

urr

en

t lo

sse

s W

ed

inte

r ( J

/m3)

Frequency f ( Hz )

Sample 1, h = 1,68mm

Sample 2, h = 3,53mm

0 5000 10000 15000 20000 25000

0

1

2

3

4

5

Exce

ss lo

sse

s W

exc (

J/m

3)

Frequency f ( Hz )

Sample 1, h = 1,68mm

Sample 2, h = 3,53mm

Fig. 4. Loss separation per unit volume

as a function of frequency for sample 2

(Fe+PFRB, h = 3,53mm), measured at

maximum induction 0.1T in the frequency

range from 2800Hz to 22000Hz.. The

hysteresis Wh, intra eddy current Wedintra,

inter eddy current Wedinter, and excess

Wexc loss components involved in loss

separation are indicated.

Fig. 5. Total losses W as a function of frequency for two samples Fe+PFRB with different

height measured at maximum induction 0.1 T in the frequency range from 2800Hz to 22000Hz.

Fig. 6. Excess losses Wexc as a function

of frequency for two samples Fe+PFRB

with different height measured at

maximum induction 0.1T in the frequency

range from 2800Hz to 22000Hz.

Fig. 7. Inter eddy current losses Wedinter

as a function of frequency for two

samples Fe+PFRB with different height

measured at maximum induction 0.1 T in

the frequency range from 2800Hz to

22000Hz.

Sample 1 ( h = 1,68 mm ) Sample 2 ( h = 3,53 mm )

f ( Hz ) Wt Wh Wedintra Wed

inter Wexc Wt Wh Wedintra Wed

inter Wexc

( J/m3 ) ( J/m3 ) ( J/m3 ) ( J/m3 ) ( J/m3 ) ( J/m3 ) ( J/m3 ) ( J/m3 ) ( J/m3 ) ( J/m3 )

3600 32,11 29,82 1,92 0,23 0,14 34,45 31,77 1,92 0,31 0,45

6200 34,20 29,82 3,31 0,39 0,68 37,04 31,77 3,31 0,54 1,43

10000 37,08 29,82 5,33 0,63 1,30 40,25 31,77 5,33 0,87 2,28

17000 42,15 29,82 9,06 1,07 2,20 45,73 31,77 9,06 1,48 3,42

Table 2. Power loss separation for two samples Fe+PFRB with different height. 𝑷𝒆𝒅

𝒊𝒏𝒕𝒓𝒂 =𝝅𝒅𝑭𝒆𝑩𝒎𝒇 𝟐

𝟐𝟎𝝆𝑭𝒆𝝆𝑹 𝑾/𝒌𝒈 𝑷𝒆𝒅

𝒊𝒏𝒕𝒆𝒓 = 𝝅𝒅𝒆𝒇𝑩𝒎𝒇

𝟐

𝜷𝝆𝝆𝒔 𝑾/𝒌𝒈

𝑾𝒕 = 𝑾𝒉𝒚𝒔 + 𝑾𝒆𝒅𝒊𝒏𝒕𝒓𝒂 + 𝑾𝒆𝒅

𝒊𝒏𝒕𝒆𝒓 + 𝑾𝒆𝒙𝒄 𝑱/𝒎𝟑

External diameter Internal diameter Height Density Specific resistivity Initial permeability Relaxation frequency

φext ( mm ) φint ( mm ) h ( mm ) ρ ( kg/m 3 ) ρ s ( μΩm ) μ0 ( - ) f r ( MHz )

Sample 1 24,12 17,81 1,68 6804 490 62 1,93

Sample 2 24,14 17,84 3,53 6555 877 53 1,87

Table 1. Parameters of the samples.

dFe = 104 μm

Bm = 0,1 T

ρFe = 7874 kg/m3

ρR = 0,1 μΩm

def = 1,68 mm resp. 3,15 mm

Bm = 0,1 T

β = 9,02 resp. 12,85

ρ = 6804 kg/m3 resp. 6555 kg/m3

ρs = 490 μΩm resp. 877 μΩm