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Structure and DC Superimposition Characteristic of Fe78Si9B13 Amorphous Alloys
Rare Metal Materials and Engineering Volume 44, Issue 6, June 2015 Online English edition of the Chinese language journal Cite this article as: Rare Metal Materials and Engineering, 2015, 44(6): 1340-1344.
ARTICLE
Structure and DC Superimposition Characteristic of Fe78Si9B13 Amorphous Alloys Hu Qin,
Zhu Zhenghou
Nanchang University, Nanchang 330031, China
Abstract: The structure and the DC superimposition characteristics of Fe78Si9B13 amorphous alloy were investigated. The influences of the air gap length and permanent magnet of the alloy on its DC superimposition characteristics were analyzed. The amorphous alloy was characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and 3D high depth of field microscope, and the DC superimposition characteristic was analyzed by means of the μ-H curves. The results show that the magnetic permeability and the saturation magnetic field intensity are dependent on the air gap length of the conventional core. The magnetic bias can improve the DC superimposition characteristic of the Fe78Si9B13 amorphous inductor core, and the magnetic permeability of the inductor cores is not adversely affected. By using the magnetic bias method, larger rated current may pass through the inductor core before magnetic saturation occurs, so the inductor cores in size can be reduced effectively Key words: air gap; permanent magnet; DC superimposition characteristic; amorphous alloys
Amorphous Fe-based alloys have several practical applications in transformers and inductors due to their excellent soft magnetic properties such as high permeability and high saturation magnetic flux density[1-4]. However, in some power electronic circuits, inductors often work under a large DC current value which is almost enough to cause the magnetic saturation of the inductor core, so that the magnetic permeability of the inductor core declines to a very small value. Magnetic saturation of the magnetic materials is a key problem to restrict the core size reduction, especially for the application to high current DC inductors [5, 6]. For any inductor design, the inductor size and DC superimposition characteristic are competing objectives. The DC superimposition characteristic of the inductor core refers to the core with an excellent magnetic permeability characteristic, that is, magnetic saturation does not occur with this direct current superimposition[7]. Therefore, it is desirable to reduce the volume and the mass of the inductor in many applications, and the inductor core does not become magnetically saturated under the large rated current value.
To improve the DC superimposition characteristic of the inductor core, a conventional method is to provide an air gap within the inductor core magnetic circuit. The presence of an air gap serves to increase the overall reluctance of the inductor core so that a larger rated current value is required to saturate the inductor core. However, the presence of air gap reduces the magnetic permeability of the inductor core, thereby decreasing the inductance of the inductor [7]. Thus, to obtain the same inductance, the air gap inductor must have a larger magnetic circuit in comparison to the closed magnetic circuit inductor, thereby increasing the inductor cost. In this paper, the magnetic bias method is used to improve the DC superimposition characteristic of the inductor core[8, 9]. By partial counteracting the DC magnetic flux produced by inductor winding current, reduced inductor mass can be achieved since a smaller core cross-sectional area can be used without saturating the magnetic core material at the rated current, and the magnetic bias does not increase the core reluctance so that the magnetic permeability of the inductor core is not
Received date: June 19, 2014 Foundation item: National Natural Science Foundation of China (60961001); Major State Basic Research Program of China (2010CB635112) Corresponding author: Zhu Zhenghou, Ph. D., Professor, College of Materials Science & Engineering, Nanchang University, Nanchang 330031, P. R. China, Tel: 0086-791-83969329, E-mail: [email protected] Copyright © 2015, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.
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Hu Qin et al. / Rare Metal Materials and Engineering, 2015, 44(6): 1340-1344
adversely affected.
1 Basic Construction and Operating Principles
Core
The schematic of the magnetic bias method to use permanent magnet for the inductor core is shown in Fig.1. The inductor includes an amorphous core with one air gap, a coil having at least one turn and a bias permanent magnet, which is inserted into the air gap of the amorphous core to apply a magnetic bias to the core. The direction of the magnetic field generated by the permanent magnet is opposite to that generated by the inductor winding current. The inductance L s of the core is given by: 0 e Ae N 2 (1 ) Ls
N S
Magnet Coil Magnetic flux of magnet Magnetic flux of coil
Fig.1
Schematic of permanent magnet bias method
B
le
Where N is the number of coil turns, Ae, le and μe are the effective cross-sectional area, the effective magnetic circuit length and effective magnetic permeability of the inductor core, respectively. The formula (2) is derived from formula (1), where D is the outer diameter, d is the inner diameter, and h is the width of the ribbon. Ls ( D d ) (2) e 107 4 N 2 h( D d ) The superimposed magnetic field intensity H generated by the inductor winding current is as follows: NI (3) H le Where N is the number of coil turns, le is the magnetic circuit length of the inductor core, and I is the current value in the coil. The relationship between magnetic flux density B and magnetic field intensity H is the important property of the magnetic materials. Fig.2 shows the hysteresis loops of the inductor cores. As shown in Fig.2, the inductor core with air gap has a greater linear range than the core with no air gap, and the slope (B/H) of the curve for the air gap inductor core decreases, the air gap inductor core achieving saturation needs larger magnetic field intensity H. From formula (3), the magnetic field intensity H is proportional to the current value I and N, therefore a larger rated current value is required to generate saturation of the air gap inductor core as compared to the no air gap inductor core. However, the air gap in the magnetic circuit reduces the magnetic permeability of the inductor core because of the reduced slope (B/H) of the curve. The working range of the inductor core is shown in Fig.3. In each figure, the inductor working range is represented by the shaded area under the curve. As shown in Fig.3a and 3b, the magnet bias inductor core may be seen to have a much greater working range as compared to the air gap inductor core (hereafter briefly referred to as “conventional core”), and therefore a larger rated current value can pass through the inductor core before saturation occurs.
a
B1
0
Fig.2
H1
b
H2
H
Hysteresis loops of the no air gap core (a) and the air gap core (b) a
B
0
Fig.3
H
B
b
0
0′
H
Working range of the air gap core (a) and the magnetic bias core (b)
2
Experiment
The amorphous ribbons with nominal composition Fe78Si9B13 with 30 µm thickness and 12.5 mm width were obtained by the melt spinning technique in air atmosphere. The ribbons were wound into toroidally the wound cores with 40 mm outer diameter and 20 mm inner diameter. Annealing of these specimens were carried out in a quartz ampoule in vacuum, at the temperature of 390 ºC for 30 min, in order to release inner stress and achieve the best soft magnetic properties. The permanent magnets were NdFeB sintered magnets, and the magnet was inserted into the air gap, and the thickness of inserted magnet suited to the air gap length, the coil of 55 turns was uniformly distributed on the toroidal magnetic core.
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The structures of amorphous specimens were analyzed by X-ray diffraction using Co Kα radiation. All XRD measurements were performed on the matte side of the ribbon specimens. The thermal stability of the as-quenched samples Fe 78Si9B13 was measured by Q-600 DSC-TGA at a heating rate of 10 ºC/min. Surface morphology was observed by 3D high depth of field microscope using a VHX-100. The DC superimposition characteristic of the inductor cores were measured by LCR digital electric bridge (TH2816B) and DC bias current source (TH1775).
3
Results and Discussion
The XRD patterns for the Fe 78Si9B13 amorphous ribbons are shown in Fig.4. Only one broad peak near 2θ=45° is noted and no diffraction peaks corresponding to crystalline phases are detected. The ribbons in the initial state have single-phase amorphous structure obtained by the melt spinning technique. The Fe 78Si9B13 ribbons have single-phase amorphous structure after annealed at 390 ºC (structural relaxation) and achieve the best soft magnetic properties due to the stress relief caused by structural relaxation[10]. The DSC curve of the as-quenched Fe 78Si9B13 amorphous ribbon is shown in Fig.5. The results show that the crystallization temperature is around 509 ºC, and the curve exhibits clearly two exothermal peak, T P1=519 ºC and TP2=537 ºC. So twice phase transition of the sample takes place in the process of crystallization. During the preparation process of the alloy ribbons, the surface which is not in direct contact with the copper wheel undergoes a more regular cooling, so this side is able to retain the shape of the liquid layer from which it comes, and in the literature [11] this side is called “shiny side”, while the other side in contact with the cooled cooper wheel called “matte side”. Fig.6 shows the surface on each side of Fe 78 Si 9 B 13 amorphous alloy ribbons. The shiny side has no obvious defects, the matte side has some surface defects such as air
pockets and impurities and it appears to have a higher degree of roughness than shiny side. Due to the molten
liquid in contact with the cooper wheel, the matte side is affected by the surface impurities and roughness of the cooper wheel, so the matte side has some surface defects and the surface is dull. The shiny side retains the shape of the molten liquid layer, has no obvious defects and the surface is shiny. Fig.7 shows the DC superimposition characteristic of conventional inductor cores at different air gap lengths. As shown in Fig.7, with the increase of the air gap length, the magnetic permeability of inductor cores decreases and the saturation magnetic field intensity increases. When the air gap length is 5.0 mm, the magnetic permeability declines to a small value and remains unchanged with the magnetic field intensity increasing. When the air gap length is excessively reduced, the DC superimposition characteristic is degraded, and when the gap length is excessively increased, the magnetic permeability is excessively reduced. This is because the resistance of the air gap to the magnetic flux is larger, the overall reluctance of the magnetic circuit increases after gapped, so that the magnetic permeability of the inductor cores decreases and larger rated current may pass through the inductor core before magnetic saturation occurs. Therefore the magnetic permeability and the saturation magnetic field intensity can be adjusted by changing the air gap length of the inductor cores. The permanent magnet is inserted into the air gap of the amorphous core to generate an opposite magnetic field to offset a portion of the magnetic field generated by the excitation coil. The DC superimposition characteristics for the conventional and magnet bias inductor cores are shown in Fig.8. The air gap length of these inductor cores is 4 mm, and the surface magnetic field of permanent magnet A1 and magnet A2 are 1663 and 2908 Gs, respectively. As shown in Fig.8, the magnetic permeability of the magnet bias cores in the initial magnetic field is the same as that of the 0.8
Heat Flow/W·g
-1
TP2=537
o
Intensity/a.u.
Annealed at 390 C
o
C
TP1=519 ℃
0.0 -0.4
Tx1=509
o
C
-0.8 As-quenched
20
30
40
50 60 o 2/( )
70
80
-1.2 400
90 Fig.5
Fig.4
0.4
XRD patterns of the Fe 78Si13B9 amorphous ribbons
450
500 550 600 o Temperature/ C
650
700
The DSC curve of the as-quenched Fe78Si 9B13 amorphous ribbons
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Hu Qin et al. / Rare Metal Materials and Engineering, 2015, 44(6): 1340-1344
a
120
b
at 25 kHz
100
C
80 60
A:conventional core with 4mm air gap length B:magnet bias core with 4mm air gap length C:magnet bias core with 2mm air gap length
40 20 Fig.6
at 25 kHz
amorphous ribbons: (a) shiny side and (b) matte side
180 160 140 120 100 80 60 40 20
2000 4000 6000 8000 10000 12000 -1 H/A· m
DC superimposed characteristic of conventional inductor cores at different air gap lengths
84
at 25 kHz
72 A
60 B
C
48 36 24 12
-8000 Fig.8
Fig.9
3000
6000 9000 -1 H/A·m
B
12000
DC superimposition characteristics for conventional and magnet bias inductor cores at different air gap lengths
1.0 mm 2.5 mm 5.0 mm
0 Fig.7
0
Surface micrographs for each side of annealed Fe78Si9B13
A
A:conventional core B:magnet A1 bias core C:magnet A2 bias core
0 -1 H/A·m
8000
DC superimposition characteristics for conventional and magnet bias inductor cores
conventional core, in the magnetic field of 8000 A/m, the magnetic permeability of the magnet A2 bias core is higher than the magnet A1 bias core and the conventional core, so the DC superimposition characteristic of the magnet A2 bias core is the best. When the surface magnetic field of the permanent magnet is larger, the magnet bias effect of the inductor core is better, and the permanent magnet in the air gap of the inductor core does not increase the inductor reluctance so that the inductor inductance is not adversely affected. Fig.9 shows the DC superimposition characteristics of
the different air gap lengths and different thickness bias magnet cores. The surface magnetic fields of the bias magnet in the cores with 2 mm air gap length and 4 mm air gap length are 1663 and 2908 Gs, respectively. In comparison with the conventional core with 4 mm air gap length, the initial permeability of the magnet bias core with same air gap length remains unchanged but the saturation magnetic field is larger, and the magnet bias core with 2 mm air gap length is improved in the aspect of initial permeability, and the saturation magnetic field is the same as that of the conventional core. Therefore under the same saturation magnetic field conditions, the cores with larger magnetic permeability can be reduced in size or the number of the turns for the inductor core design. The magnetic bias method using the permanent magnet can improve the DC superimposition characteristic of the inductor core, and it can miniaturize the inductor core which is the indispensable circuit component for electric power source units, so the size and the mass of the electric power source units can be reduced.
4
Conclusions
1) The magnetic permeability of the inductor core decreases with the increase of the air gap length, and the saturation magnetic field intensity is larger, when the air gap length is 2.5 mm; the magnetic permeability declines to a small value and remains unchanged with the increase of the magnetic field intensity. 2) The DC superimposition characteristics of the inductor cores can be improved by the magnetic bias. The bias magnet does not adversely affect the magnetic permeability of the inductor cores but can increase the saturation magnetic field intensity. The surface magnetic field of the permanent magnet is larger, and the magnet bias effect is excellent. 3) By the magnetic bias method, the inductor cores can be reduced in size or the number of the turns easily for the inductor design.
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References 1
Makino A, Inoue A, Mizushima T. Materials Transactions[J], 2000, 41(11): 1471
2
Ogawa Y, Naoe M, Yoshizawa Y et al. Journal of Magnetism and Magnetic Materials[J], 2006, 304(2): e675
3
Zhou P H, Xie J L, Liu Y Q et al. Journal of Magnetism and Magnetic Materials[J], 2008, 320(24): 3390
4
Li Xiang, Yan Biao, Xiang Qiuwei et al. Rare Metal Materials and Engineering[J], 2011, 40(3): 495 (in Chinese)
5
Fujiwara T, Matsumoto H. Telecommunications Energy
6
Wrobel R, Mcneill N, Mellor P H. Power Electronics
7
Fujiwara T, Ishii M, Hoshi H et al. US Patent, 6753751[P].
Specialists Conference[C]. Rhodes, Greece: IEEE, 2008: 3171 2004 8
Pieteris P. European Patent, EP2216794[P]. 2011
9
Hansen T T. US Patent, 0298572[P]. 2011
10
Baron A, Szewieczek D, Nawrat G. Electrochimica Acta[J], 2007, 52(18): 5690
11
Szewieczek D, Baron A. Journal of Materials Processing Technology[J], 2006, 175(1-3): 411
Conference[C]. Brazil: IEEE, 2003: 416
1344
ARTICLE
Structure and DC Superimposition Characteristic of Fe78Si9B13 Amorphous Alloys Hu Qin,
Zhu Zhenghou
Nanchang University, Nanchang 330031, China
Abstract: The structure and the DC superimposition characteristics of Fe78Si9B13 amorphous alloy were investigated. The influences of the air gap length and permanent magnet of the alloy on its DC superimposition characteristics were analyzed. The amorphous alloy was characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and 3D high depth of field microscope, and the DC superimposition characteristic was analyzed by means of the μ-H curves. The results show that the magnetic permeability and the saturation magnetic field intensity are dependent on the air gap length of the conventional core. The magnetic bias can improve the DC superimposition characteristic of the Fe78Si9B13 amorphous inductor core, and the magnetic permeability of the inductor cores is not adversely affected. By using the magnetic bias method, larger rated current may pass through the inductor core before magnetic saturation occurs, so the inductor cores in size can be reduced effectively Key words: air gap; permanent magnet; DC superimposition characteristic; amorphous alloys
Amorphous Fe-based alloys have several practical applications in transformers and inductors due to their excellent soft magnetic properties such as high permeability and high saturation magnetic flux density[1-4]. However, in some power electronic circuits, inductors often work under a large DC current value which is almost enough to cause the magnetic saturation of the inductor core, so that the magnetic permeability of the inductor core declines to a very small value. Magnetic saturation of the magnetic materials is a key problem to restrict the core size reduction, especially for the application to high current DC inductors [5, 6]. For any inductor design, the inductor size and DC superimposition characteristic are competing objectives. The DC superimposition characteristic of the inductor core refers to the core with an excellent magnetic permeability characteristic, that is, magnetic saturation does not occur with this direct current superimposition[7]. Therefore, it is desirable to reduce the volume and the mass of the inductor in many applications, and the inductor core does not become magnetically saturated under the large rated current value.
To improve the DC superimposition characteristic of the inductor core, a conventional method is to provide an air gap within the inductor core magnetic circuit. The presence of an air gap serves to increase the overall reluctance of the inductor core so that a larger rated current value is required to saturate the inductor core. However, the presence of air gap reduces the magnetic permeability of the inductor core, thereby decreasing the inductance of the inductor [7]. Thus, to obtain the same inductance, the air gap inductor must have a larger magnetic circuit in comparison to the closed magnetic circuit inductor, thereby increasing the inductor cost. In this paper, the magnetic bias method is used to improve the DC superimposition characteristic of the inductor core[8, 9]. By partial counteracting the DC magnetic flux produced by inductor winding current, reduced inductor mass can be achieved since a smaller core cross-sectional area can be used without saturating the magnetic core material at the rated current, and the magnetic bias does not increase the core reluctance so that the magnetic permeability of the inductor core is not
Received date: June 19, 2014 Foundation item: National Natural Science Foundation of China (60961001); Major State Basic Research Program of China (2010CB635112) Corresponding author: Zhu Zhenghou, Ph. D., Professor, College of Materials Science & Engineering, Nanchang University, Nanchang 330031, P. R. China, Tel: 0086-791-83969329, E-mail: [email protected] Copyright © 2015, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.
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Hu Qin et al. / Rare Metal Materials and Engineering, 2015, 44(6): 1340-1344
adversely affected.
1 Basic Construction and Operating Principles
Core
The schematic of the magnetic bias method to use permanent magnet for the inductor core is shown in Fig.1. The inductor includes an amorphous core with one air gap, a coil having at least one turn and a bias permanent magnet, which is inserted into the air gap of the amorphous core to apply a magnetic bias to the core. The direction of the magnetic field generated by the permanent magnet is opposite to that generated by the inductor winding current. The inductance L s of the core is given by: 0 e Ae N 2 (1 ) Ls
N S
Magnet Coil Magnetic flux of magnet Magnetic flux of coil
Fig.1
Schematic of permanent magnet bias method
B
le
Where N is the number of coil turns, Ae, le and μe are the effective cross-sectional area, the effective magnetic circuit length and effective magnetic permeability of the inductor core, respectively. The formula (2) is derived from formula (1), where D is the outer diameter, d is the inner diameter, and h is the width of the ribbon. Ls ( D d ) (2) e 107 4 N 2 h( D d ) The superimposed magnetic field intensity H generated by the inductor winding current is as follows: NI (3) H le Where N is the number of coil turns, le is the magnetic circuit length of the inductor core, and I is the current value in the coil. The relationship between magnetic flux density B and magnetic field intensity H is the important property of the magnetic materials. Fig.2 shows the hysteresis loops of the inductor cores. As shown in Fig.2, the inductor core with air gap has a greater linear range than the core with no air gap, and the slope (B/H) of the curve for the air gap inductor core decreases, the air gap inductor core achieving saturation needs larger magnetic field intensity H. From formula (3), the magnetic field intensity H is proportional to the current value I and N, therefore a larger rated current value is required to generate saturation of the air gap inductor core as compared to the no air gap inductor core. However, the air gap in the magnetic circuit reduces the magnetic permeability of the inductor core because of the reduced slope (B/H) of the curve. The working range of the inductor core is shown in Fig.3. In each figure, the inductor working range is represented by the shaded area under the curve. As shown in Fig.3a and 3b, the magnet bias inductor core may be seen to have a much greater working range as compared to the air gap inductor core (hereafter briefly referred to as “conventional core”), and therefore a larger rated current value can pass through the inductor core before saturation occurs.
a
B1
0
Fig.2
H1
b
H2
H
Hysteresis loops of the no air gap core (a) and the air gap core (b) a
B
0
Fig.3
H
B
b
0
0′
H
Working range of the air gap core (a) and the magnetic bias core (b)
2
Experiment
The amorphous ribbons with nominal composition Fe78Si9B13 with 30 µm thickness and 12.5 mm width were obtained by the melt spinning technique in air atmosphere. The ribbons were wound into toroidally the wound cores with 40 mm outer diameter and 20 mm inner diameter. Annealing of these specimens were carried out in a quartz ampoule in vacuum, at the temperature of 390 ºC for 30 min, in order to release inner stress and achieve the best soft magnetic properties. The permanent magnets were NdFeB sintered magnets, and the magnet was inserted into the air gap, and the thickness of inserted magnet suited to the air gap length, the coil of 55 turns was uniformly distributed on the toroidal magnetic core.
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The structures of amorphous specimens were analyzed by X-ray diffraction using Co Kα radiation. All XRD measurements were performed on the matte side of the ribbon specimens. The thermal stability of the as-quenched samples Fe 78Si9B13 was measured by Q-600 DSC-TGA at a heating rate of 10 ºC/min. Surface morphology was observed by 3D high depth of field microscope using a VHX-100. The DC superimposition characteristic of the inductor cores were measured by LCR digital electric bridge (TH2816B) and DC bias current source (TH1775).
3
Results and Discussion
The XRD patterns for the Fe 78Si9B13 amorphous ribbons are shown in Fig.4. Only one broad peak near 2θ=45° is noted and no diffraction peaks corresponding to crystalline phases are detected. The ribbons in the initial state have single-phase amorphous structure obtained by the melt spinning technique. The Fe 78Si9B13 ribbons have single-phase amorphous structure after annealed at 390 ºC (structural relaxation) and achieve the best soft magnetic properties due to the stress relief caused by structural relaxation[10]. The DSC curve of the as-quenched Fe 78Si9B13 amorphous ribbon is shown in Fig.5. The results show that the crystallization temperature is around 509 ºC, and the curve exhibits clearly two exothermal peak, T P1=519 ºC and TP2=537 ºC. So twice phase transition of the sample takes place in the process of crystallization. During the preparation process of the alloy ribbons, the surface which is not in direct contact with the copper wheel undergoes a more regular cooling, so this side is able to retain the shape of the liquid layer from which it comes, and in the literature [11] this side is called “shiny side”, while the other side in contact with the cooled cooper wheel called “matte side”. Fig.6 shows the surface on each side of Fe 78 Si 9 B 13 amorphous alloy ribbons. The shiny side has no obvious defects, the matte side has some surface defects such as air
pockets and impurities and it appears to have a higher degree of roughness than shiny side. Due to the molten
liquid in contact with the cooper wheel, the matte side is affected by the surface impurities and roughness of the cooper wheel, so the matte side has some surface defects and the surface is dull. The shiny side retains the shape of the molten liquid layer, has no obvious defects and the surface is shiny. Fig.7 shows the DC superimposition characteristic of conventional inductor cores at different air gap lengths. As shown in Fig.7, with the increase of the air gap length, the magnetic permeability of inductor cores decreases and the saturation magnetic field intensity increases. When the air gap length is 5.0 mm, the magnetic permeability declines to a small value and remains unchanged with the magnetic field intensity increasing. When the air gap length is excessively reduced, the DC superimposition characteristic is degraded, and when the gap length is excessively increased, the magnetic permeability is excessively reduced. This is because the resistance of the air gap to the magnetic flux is larger, the overall reluctance of the magnetic circuit increases after gapped, so that the magnetic permeability of the inductor cores decreases and larger rated current may pass through the inductor core before magnetic saturation occurs. Therefore the magnetic permeability and the saturation magnetic field intensity can be adjusted by changing the air gap length of the inductor cores. The permanent magnet is inserted into the air gap of the amorphous core to generate an opposite magnetic field to offset a portion of the magnetic field generated by the excitation coil. The DC superimposition characteristics for the conventional and magnet bias inductor cores are shown in Fig.8. The air gap length of these inductor cores is 4 mm, and the surface magnetic field of permanent magnet A1 and magnet A2 are 1663 and 2908 Gs, respectively. As shown in Fig.8, the magnetic permeability of the magnet bias cores in the initial magnetic field is the same as that of the 0.8
Heat Flow/W·g
-1
TP2=537
o
Intensity/a.u.
Annealed at 390 C
o
C
TP1=519 ℃
0.0 -0.4
Tx1=509
o
C
-0.8 As-quenched
20
30
40
50 60 o 2/( )
70
80
-1.2 400
90 Fig.5
Fig.4
0.4
XRD patterns of the Fe 78Si13B9 amorphous ribbons
450
500 550 600 o Temperature/ C
650
700
The DSC curve of the as-quenched Fe78Si 9B13 amorphous ribbons
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Hu Qin et al. / Rare Metal Materials and Engineering, 2015, 44(6): 1340-1344
a
120
b
at 25 kHz
100
C
80 60
A:conventional core with 4mm air gap length B:magnet bias core with 4mm air gap length C:magnet bias core with 2mm air gap length
40 20 Fig.6
at 25 kHz
amorphous ribbons: (a) shiny side and (b) matte side
180 160 140 120 100 80 60 40 20
2000 4000 6000 8000 10000 12000 -1 H/A· m
DC superimposed characteristic of conventional inductor cores at different air gap lengths
84
at 25 kHz
72 A
60 B
C
48 36 24 12
-8000 Fig.8
Fig.9
3000
6000 9000 -1 H/A·m
B
12000
DC superimposition characteristics for conventional and magnet bias inductor cores at different air gap lengths
1.0 mm 2.5 mm 5.0 mm
0 Fig.7
0
Surface micrographs for each side of annealed Fe78Si9B13
A
A:conventional core B:magnet A1 bias core C:magnet A2 bias core
0 -1 H/A·m
8000
DC superimposition characteristics for conventional and magnet bias inductor cores
conventional core, in the magnetic field of 8000 A/m, the magnetic permeability of the magnet A2 bias core is higher than the magnet A1 bias core and the conventional core, so the DC superimposition characteristic of the magnet A2 bias core is the best. When the surface magnetic field of the permanent magnet is larger, the magnet bias effect of the inductor core is better, and the permanent magnet in the air gap of the inductor core does not increase the inductor reluctance so that the inductor inductance is not adversely affected. Fig.9 shows the DC superimposition characteristics of
the different air gap lengths and different thickness bias magnet cores. The surface magnetic fields of the bias magnet in the cores with 2 mm air gap length and 4 mm air gap length are 1663 and 2908 Gs, respectively. In comparison with the conventional core with 4 mm air gap length, the initial permeability of the magnet bias core with same air gap length remains unchanged but the saturation magnetic field is larger, and the magnet bias core with 2 mm air gap length is improved in the aspect of initial permeability, and the saturation magnetic field is the same as that of the conventional core. Therefore under the same saturation magnetic field conditions, the cores with larger magnetic permeability can be reduced in size or the number of the turns for the inductor core design. The magnetic bias method using the permanent magnet can improve the DC superimposition characteristic of the inductor core, and it can miniaturize the inductor core which is the indispensable circuit component for electric power source units, so the size and the mass of the electric power source units can be reduced.
4
Conclusions
1) The magnetic permeability of the inductor core decreases with the increase of the air gap length, and the saturation magnetic field intensity is larger, when the air gap length is 2.5 mm; the magnetic permeability declines to a small value and remains unchanged with the increase of the magnetic field intensity. 2) The DC superimposition characteristics of the inductor cores can be improved by the magnetic bias. The bias magnet does not adversely affect the magnetic permeability of the inductor cores but can increase the saturation magnetic field intensity. The surface magnetic field of the permanent magnet is larger, and the magnet bias effect is excellent. 3) By the magnetic bias method, the inductor cores can be reduced in size or the number of the turns easily for the inductor design.
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Hu Qin et al. / Rare Metal Materials and Engineering, 2015, 44(6): 1340-1344
References 1
Makino A, Inoue A, Mizushima T. Materials Transactions[J], 2000, 41(11): 1471
2
Ogawa Y, Naoe M, Yoshizawa Y et al. Journal of Magnetism and Magnetic Materials[J], 2006, 304(2): e675
3
Zhou P H, Xie J L, Liu Y Q et al. Journal of Magnetism and Magnetic Materials[J], 2008, 320(24): 3390
4
Li Xiang, Yan Biao, Xiang Qiuwei et al. Rare Metal Materials and Engineering[J], 2011, 40(3): 495 (in Chinese)
5
Fujiwara T, Matsumoto H. Telecommunications Energy
6
Wrobel R, Mcneill N, Mellor P H. Power Electronics
7
Fujiwara T, Ishii M, Hoshi H et al. US Patent, 6753751[P].
Specialists Conference[C]. Rhodes, Greece: IEEE, 2008: 3171 2004 8
Pieteris P. European Patent, EP2216794[P]. 2011
9
Hansen T T. US Patent, 0298572[P]. 2011
10
Baron A, Szewieczek D, Nawrat G. Electrochimica Acta[J], 2007, 52(18): 5690
11
Szewieczek D, Baron A. Journal of Materials Processing Technology[J], 2006, 175(1-3): 411
Conference[C]. Brazil: IEEE, 2003: 416
1344