Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2001-05-30
2002-05-14
Koehler, Robert R. (Department: 1775)
Stock material or miscellaneous articles
Composite
Of metal
C029S602100, C148S100000, C148S113000, C336S218000, C427S104000, C427S127000, C428S900000, C428S926000, C428S928000
Reexamination Certificate
active
06387522
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrical steel sheet, for a low noise transformer excellent in magnetostriction property, used for an iron core of a transformer and the like.
2. Description of the Related Art
In magnetic materials widely used for electrical and electronic apparatuses the lengths change when a magnetic field is applied (this is referred to as “magnetostriction”) to cause of transformer noise and the extent thereof has become an important evaluation item in quality control. In recent years, regulation of noise generated by electrical apparatuses is becoming stricter with an increased demand for a better living environment. Therefore, studies for lowering noise, by decreasing magnetostriction, are being carried out.
Among magnetic materials, for grain-oriented electrical steel sheets used for iron cores of transformers, a means for decreasing magnetostriction by reducing closure domains has been applied. The term “closure domains” as cited here means domains having magnetization oriented in the direction perpendicular to the direction of an applied magnetic field. Magnetostriction is caused when this magnetization is turned to a direction parallel to the magnetic field by an applied magnetic field. Accordingly, the fewer the closure domains, the smaller the magnetostriction. The following methods are known as means for decreasing magnetostriction:
{circle around (1)} a method for avoiding the formation of closure domains, that cause shape changes by magnetization rotation, by means of aligning the <001> direction of crystal grains with the rolling direction. (T. Nozawa et al, “Relationship between Total Losses under Tensile Stress in 3 Percent Si—Fe Single Crystals and Their Orientations near (110) [001],” IEEE Trans. on Mag., Vol. MAG-14, No.4, 1978),
{circle around (2)} a method for eliminating closure domains by releasing plastic strains (Japanese Unexamined Patent Publication No. H7-305115, [Development of Revolutionary Oriented Silicon Steel Sheet, ORIENTCORE HI-B]: OHM 1972. 2), and
{circle around (3)} a method for eliminating closure domains by applying a tension film to a steel sheet (T. Nozawa et al, “Relationship between Total Losses under Tensile Stress in 3 Percent Si—Fe Single Crystals and Their Orientations near (110) [001],”IEEE Trans. on Mag., Vol. MAG-14, No.4, 1978).
These three methods have decreased magnetostriction and have contributed to lowering the noise of electrical apparatuses.
SUMMARY OF THE INVENTION
When a transformer is fabricated from a grain-oriented electrical steel sheet and magnetized, various modes of vibrations are generated in the structure and the oscillation frequencies of harmonics are also generated. In particular, a fundamental frequency of magnetization (for example, 100 Hz in the case of an exciting current of 50 Hz in frequency) and frequencies obtained by multiplying the fundamental frequency by integral numbers (for example, 200, 300, 400 Hz—in the case of an exciting current of 50 Hz in frequency) have especially high intensity among transformer noises. Among these frequencies, relatively low frequency components vibrate an iron core proper directly, while high frequency components resonate the auxiliary units of a transformer, such as a tank, a chiller, a conservator and the like. However, since the vibrations decrease heir intensity exponentially and become less influential at higher frequencies, technologies for reducing the low-frequency components have mainly been tackled so far.
However, demands for further lowering the noise are strong and more sophisticated technologies are required.
The object of the present invention is to provide an electrical steel sheet, for a low noise transformer, excellent in magnetostriction properties, capable of reducing high frequency components in a magnetostriction waveform and lowering noise effectively.
The embodiments of the present invention are as follows:
(1) A grain-oriented electrical steel sheet for a low noise transformer, having a film that imposes a tension of 0.5 MPa to 4.0 MPa on the steel sheet.
(2) A method for producing a grain-oriented electrical steel sheet for a low noise transformer, characterized by imposing a film tension of 0.5 MPa to 4.0 MPa on the surface by coating or a method corresponding thereto, without forming a glass film on the grain-oriented electrical steel sheet or, if a glass film is formed, after removing the glass film by an arbitrary method.
(3) A grain-oriented electrical steel sheet for a low noise transformer characterized by having a &lgr;
19
of 1.5×10
−6
or less.
(4) A grain-oriented electrical steel sheet for a low noise transformer according to the item (1) or (3), characterized by having a sheet thickness of 0.27 mm or more.
REFERENCES:
patent: 3932236 (1976-01-01), Wada et al.
patent: 5961744 (1999-10-01), Yamazaki et al.
patent: 7-305115 (1995-11-01), None
IEEE Transactions on Magnetics, vol. Mag-14, No. 4, “Relationship Between Total Losses Under Tensile Stress in 3 Percent Si-Fe Single Crystals and their Orientations Near (110) [001]”, Tadao Nozawa, et al., Dec. 1978.
OHM, vol. 59, No. 2, pp. 1-7, Dec. 1972.
Journal of Magnetism and Magnetic Materials 160(1996), 123-124, Ultrathick Glassless High Permeability, Grain-Oriented Silicon Steel Sheets with High Woarkability, Y. Yoshitomi, et al. no month.
Fujikura Masahiro
Mizokami Masato
Mogi Hisashi
Sakaida Akira
Kenyon & Kenyon
Koehler Robert R.
Nippon Steel Corporation
LandOfFree
Grain-oriented electrical steel sheet for low-noise transformer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Grain-oriented electrical steel sheet for low-noise transformer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Grain-oriented electrical steel sheet for low-noise transformer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2864235