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Influence of magnetization pause on the magnetic properties of an electrical iron sheet
Journal of Magnetism and Magnetic Materials 160 (1996) 33-34
~ H journalof magnetism J a and magnetic ,444 materials
ELSEVIER
Influence of magnetization pause on the magnetic properties of an electrical iron sheet S. Takada, T. Sasaki * Department of Electronics, Gi/il Unit'ersity, Yanagido 1-1, Gi['u 501-11. Japan Abstract This study concerns the magnetic properties of electrical iron sheets under controlled excitation with magnetization pauses. The influence of the magnetization pause on the magnetic properties is present during the following magnetizing cycle. It is confirmed that this is caused by disturbance of the dynamic domain structure due to the pause during cyclic magnetization.
Kevwords: Electrical iron sheet; Magnetic hysteresis loop; Magnetization pause; Magnetostriction; Power loss
We have previously reported on the magnetic properties of electrical iron sheets under several controlled magnetizing conditions in which the magnetization changes at a constant time rate and, in addition, pauses of a certain duration occur in every half-magnetizing cycle as shown in Fig. la for R-excitation and Fig. lb for P-excitation. As a result, the power losses per magnetizing cycle have been found to change with pause time [1,2]. Further investigations of the influence of pause time on magnetizing processes have to be carried out to understand these loss changes. We have measured the magnetic properties of a non-oriented electrical iron sheet under controlled excitation with the waveform shown in Fig. lc, referred to as P/3-excitation, in which the magnetization pauses at the peak induction once every third half-magnetizing cycle. The sample is a washer-type non-oriented electrical iron sheet JIS50A800 (ASTM47F460) with an inner diameter of 100 ram, an outer diameter of 200 mm and a thickness of 0.35 ram. Three magnetizing conditions, R-, P- and P/3-excitation, shown in Fig. 1, are applied to the sample using a micro-computer system [3]. In this experiment, both the magnetizing period, T M, and the pause period, Tp, are fixed at 2.5 ms. Therefore, the signal frequencies for R- and P-excitation, which are identical to the magnetizing frequencies, are 200 and 100 Hz, respectively. Although the signal frequency for P/3-excitation is 50 Hz, the magnetizing frequency changes every cycle because the magnetization pauses once every three halfmagnetizing cycles. The dynamic hysteresis loop, magnetic loss and magnetostriction have been measured. Fig. 2a,b,c shows examples of B H hysteresis loops in
* Corresponding author. Fax: + 81-58-230-1109.
(a) R-excitation < li,~>
<
T
(b) P-excitation
>
<
T
.... >
(c) P/3-excitation
<2
I
2:,'<
T II
D<
III
~'
Fig. 1. Waveform of induced voltage and magnetic induction. one magnetizing cycle for R-, P- and P/3-excitation, respectively. The locus of the loop for P/3-excitation, shown in Fig. 2c, consists of three loops, shown in Fig. 2d,e,f, which correspond to magnetizing cycles I, II and III of Fig. lc, respectively. As shown in Fig. 2e, the locus for P/3-excitation is not identical for three cycles. The inner and outer loci are similar to the loops for R- and P-excitation, repectively. Table 1 shows the magnetic loss per magnetizing cycle P / f where the values for P/3-excitation are the average over three magnetizing cycles because one signal cycle consists of three magnetizing cycles. As we have reported previously [1,2], the values of P / f for P-excitation are larger than those for R-excitation, although the same losses are expected. The values for P/3-excitation are between those of R- and P-excitation. From the viewpoint of the
0304-8853/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. Pll S 0 3 0 4 - 8 8 5 3 ( 9 6 ) 0 0 0 9 8 - 4
34
S. Takada, T. Sasaki / Journal ~['Magnetism and Magnetic Materials 160 (1996) 33-34
Table 1 Magnetic losses per magnetizing cycle and maximum magnetizing forces B (T)
P / f (mJ/kg)
0.3 0.5 1.0 1.3 1.5
Hm (A/m)
R-exc.
P-exc.
P/3-exc.
R-exc.
P-exc.
P/3-exc.
13.73 31.72 103.3 164.7 228.5
14.63 33.36 106.5 172.3 236.6
13.88 32.07 104.0 166.7 231.4
182.9 225.7 403.7 656.6 1148.4
177.5 220.7 382.1 607.6 1076.2
178.9 222.6 391.0 621.3 1076.8
(a) R-excitation
(d) P/3-excitation (c
.
(a) R-excitation
~J(b) P-excitation
(e) P/3-excitation (cycleI I ) ~ A / m A/m..._) 500
(c) p/3-exeitation
/
(d) P/3-excitation(cycleI)
B (T)
~
~ B;1.0T t
(b) P-excitation
(e) P/3-excitation(cycle1I)
(c) P/3-excitation
(f) P/3-excitation(cyclem)
)
500
(f) P/3-excitation ~_~o)
(c
.
B (T)
Fig. 2. Examples of hysteresis loops (Bm = 1.0 T). B - H loops and the values of P / f , the magnetizing process for P/3-excitation is considered to transfer between the processes for R- and P-excitation. The maximum magnetizing forces H m over one magnetizing cycle are also shown in Table 1. The values of H m for R-excitation are larger than those for P-excitation. If the influence of the magnetization pause vanishes after three half-magnetizing cycles from the start of magnetization, the H m for P / 3 - e x citation is expected to be identical to those of R-excitation. The value for P/3-excitation is, however, closer to those of P-excitation than those of R-excitation. This suggests that the influence of the magnetization pause exists for at least one of the following magnetizing cycles. Fig. 3 shows an example of magnetostriction butterfly loops with their loci indicated by arrows. The locus of magnetostriction for P/3-excitation (Fig. 3c) is very complicated and is diferent in three cycles, as for B - H loops.
Fig. 3. Examples of magnetostrictive butterfly loops ( Bm = 1.0 T).
The loci for P- and P/3-excitation just after the magnetization pause are very similar, and at one magnetizing cycle after the magnetization pause the locus for P/3-excitation is similar to that for R-excitation. Thus, the dynamic domain structure is quite disturbed by insertion of the magnetization pause. On the whole, the change of the magnetizing process due to the magnetization pause remains during at least the following magnetizing cycle, during which domain wall movements are disturbed. References
[1] S. Takada and T. Sasaki, IEEE Trans. Magn. 28 (1992) 2784. [2] S. Takada and T. Sasaki, IEEE Trans. Magn. 29 (1993) 354l. [3] T. Sasaki and S. Takada, Anal. Fis. B 86 (1990) 258.
~ H journalof magnetism J a and magnetic ,444 materials
ELSEVIER
Influence of magnetization pause on the magnetic properties of an electrical iron sheet S. Takada, T. Sasaki * Department of Electronics, Gi/il Unit'ersity, Yanagido 1-1, Gi['u 501-11. Japan Abstract This study concerns the magnetic properties of electrical iron sheets under controlled excitation with magnetization pauses. The influence of the magnetization pause on the magnetic properties is present during the following magnetizing cycle. It is confirmed that this is caused by disturbance of the dynamic domain structure due to the pause during cyclic magnetization.
Kevwords: Electrical iron sheet; Magnetic hysteresis loop; Magnetization pause; Magnetostriction; Power loss
We have previously reported on the magnetic properties of electrical iron sheets under several controlled magnetizing conditions in which the magnetization changes at a constant time rate and, in addition, pauses of a certain duration occur in every half-magnetizing cycle as shown in Fig. la for R-excitation and Fig. lb for P-excitation. As a result, the power losses per magnetizing cycle have been found to change with pause time [1,2]. Further investigations of the influence of pause time on magnetizing processes have to be carried out to understand these loss changes. We have measured the magnetic properties of a non-oriented electrical iron sheet under controlled excitation with the waveform shown in Fig. lc, referred to as P/3-excitation, in which the magnetization pauses at the peak induction once every third half-magnetizing cycle. The sample is a washer-type non-oriented electrical iron sheet JIS50A800 (ASTM47F460) with an inner diameter of 100 ram, an outer diameter of 200 mm and a thickness of 0.35 ram. Three magnetizing conditions, R-, P- and P/3-excitation, shown in Fig. 1, are applied to the sample using a micro-computer system [3]. In this experiment, both the magnetizing period, T M, and the pause period, Tp, are fixed at 2.5 ms. Therefore, the signal frequencies for R- and P-excitation, which are identical to the magnetizing frequencies, are 200 and 100 Hz, respectively. Although the signal frequency for P/3-excitation is 50 Hz, the magnetizing frequency changes every cycle because the magnetization pauses once every three halfmagnetizing cycles. The dynamic hysteresis loop, magnetic loss and magnetostriction have been measured. Fig. 2a,b,c shows examples of B H hysteresis loops in
* Corresponding author. Fax: + 81-58-230-1109.
(a) R-excitation < li,~>
<
T
(b) P-excitation
>
<
T
.... >
(c) P/3-excitation
<2
I
2:,'<
T II
D<
III
~'
Fig. 1. Waveform of induced voltage and magnetic induction. one magnetizing cycle for R-, P- and P/3-excitation, respectively. The locus of the loop for P/3-excitation, shown in Fig. 2c, consists of three loops, shown in Fig. 2d,e,f, which correspond to magnetizing cycles I, II and III of Fig. lc, respectively. As shown in Fig. 2e, the locus for P/3-excitation is not identical for three cycles. The inner and outer loci are similar to the loops for R- and P-excitation, repectively. Table 1 shows the magnetic loss per magnetizing cycle P / f where the values for P/3-excitation are the average over three magnetizing cycles because one signal cycle consists of three magnetizing cycles. As we have reported previously [1,2], the values of P / f for P-excitation are larger than those for R-excitation, although the same losses are expected. The values for P/3-excitation are between those of R- and P-excitation. From the viewpoint of the
0304-8853/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. Pll S 0 3 0 4 - 8 8 5 3 ( 9 6 ) 0 0 0 9 8 - 4
34
S. Takada, T. Sasaki / Journal ~['Magnetism and Magnetic Materials 160 (1996) 33-34
Table 1 Magnetic losses per magnetizing cycle and maximum magnetizing forces B (T)
P / f (mJ/kg)
0.3 0.5 1.0 1.3 1.5
Hm (A/m)
R-exc.
P-exc.
P/3-exc.
R-exc.
P-exc.
P/3-exc.
13.73 31.72 103.3 164.7 228.5
14.63 33.36 106.5 172.3 236.6
13.88 32.07 104.0 166.7 231.4
182.9 225.7 403.7 656.6 1148.4
177.5 220.7 382.1 607.6 1076.2
178.9 222.6 391.0 621.3 1076.8
(a) R-excitation
(d) P/3-excitation (c
.
(a) R-excitation
~J(b) P-excitation
(e) P/3-excitation (cycleI I ) ~ A / m A/m..._) 500
(c) p/3-exeitation
/
(d) P/3-excitation(cycleI)
B (T)
~
~ B;1.0T t
(b) P-excitation
(e) P/3-excitation(cycle1I)
(c) P/3-excitation
(f) P/3-excitation(cyclem)
)
500
(f) P/3-excitation ~_~o)
(c
.
B (T)
Fig. 2. Examples of hysteresis loops (Bm = 1.0 T). B - H loops and the values of P / f , the magnetizing process for P/3-excitation is considered to transfer between the processes for R- and P-excitation. The maximum magnetizing forces H m over one magnetizing cycle are also shown in Table 1. The values of H m for R-excitation are larger than those for P-excitation. If the influence of the magnetization pause vanishes after three half-magnetizing cycles from the start of magnetization, the H m for P / 3 - e x citation is expected to be identical to those of R-excitation. The value for P/3-excitation is, however, closer to those of P-excitation than those of R-excitation. This suggests that the influence of the magnetization pause exists for at least one of the following magnetizing cycles. Fig. 3 shows an example of magnetostriction butterfly loops with their loci indicated by arrows. The locus of magnetostriction for P/3-excitation (Fig. 3c) is very complicated and is diferent in three cycles, as for B - H loops.
Fig. 3. Examples of magnetostrictive butterfly loops ( Bm = 1.0 T).
The loci for P- and P/3-excitation just after the magnetization pause are very similar, and at one magnetizing cycle after the magnetization pause the locus for P/3-excitation is similar to that for R-excitation. Thus, the dynamic domain structure is quite disturbed by insertion of the magnetization pause. On the whole, the change of the magnetizing process due to the magnetization pause remains during at least the following magnetizing cycle, during which domain wall movements are disturbed. References
[1] S. Takada and T. Sasaki, IEEE Trans. Magn. 28 (1992) 2784. [2] S. Takada and T. Sasaki, IEEE Trans. Magn. 29 (1993) 354l. [3] T. Sasaki and S. Takada, Anal. Fis. B 86 (1990) 258.