JPS6019129B2 - Method for improving iron loss in transformer core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving iron loss in a transformer using a competitively laminated iron core punched from a unidirectional electrical steel sheet into a CI or EI type.

When using a unidirectional electrical steel sheet for a transformer core, the most effective way to use its magnetic properties is to create a wound core structure, but winding the wound core is not easy, so from this point of view A regular CI or EI core is preferred.

However, in a CI or EI core, since the two sides are perpendicular to each other, if one side is selected in the direction of the easy axis of magnetization, the other side will not be in the direction of the easy axis of magnetization. To avoid this, all C-type or E-type members should be constructed from a combination of type 1 members, but in this case, many butt parts of type 1 members will occur, and naturally there will be gaps in the butt parts, making it large. Introducing magnetic resistance.
There is also bidirectional electrical steel sheet, but this is not yet at a stage where it can be mass-produced at low cost.

Therefore, it is currently desired to develop a method that uses unidirectional electrical steel sheets that can be mass-produced at low cost and improves the characteristics through appropriate treatment to produce a CLEI core that can exhibit performance close to that of a wound core. The present invention attempts to meet these demands and attempts to obtain desired characteristics using pulsed laser light.

Next, this will be explained in detail with reference to the drawings. As is well known, a unidirectional electrical steel sheet has a (110)[001] structure and is easily magnetized in the rolling direction.

When the steel plate 101 is irradiated with pulsed laser light perpendicular to the rolling direction F in the form of a line, chain line, dotted line, etc. as shown in FIG. (showing the irradiated part) Iron loss is reduced. This can be explained as follows. That is, the unidirectional electrical steel sheet 10 is shown in FIG.
As shown in the figure, it has a relatively large magnetic domain 14 extending in the rolling direction. In unidirectional electrical steel sheets, (110) [00
1] As the degree of accumulation of orientation in the rolling direction increases, the crystal grains become larger, and the magnetic domain becomes larger because the wall penetrates the grain boundary, and there is a proportional relationship between the size of the magnetic domain and the iron loss value. There is a paradoxical problem in that the iron loss does not decrease even if the directionality is increased. On the other hand,
When the laser beam is irradiated in a direction substantially perpendicular to the rolling direction, protrusions 16 are generated on both sides of the irradiated portion 12. This can be observed using a scanning electron microscope or the like. Note that in the figure, only a portion of the small protrusions are shown for simplicity. This small protrusion is a bud of a magnetic domain, and when magnetized, the magnetic domain 14 of the steel plate 10 extends from this bud.
Subdivided by. Therefore, iron loss becomes small. It is thought that the small protrusions 16 are formed because dislocations occur when the steel plate 10' is irradiated with pulsed laser light, and the probability of occurrence of magnetic domain buds is proportional to the density of these dislocations. When laser light is irradiated in the rolling direction as shown in FIG. 1b, small protrusions 16, which are buds of magnetic domains, are generated as shown in FIG. 2b.

It is thought that when an external magnetic field acts, minute domains are generated from these sprouts 16, which lowers the iron loss. To give a specific example, iron loss WL in the rolling direction (magnetic flux density 1.
Frequency 50HZ) is 1.00W/k9, and iron loss Wc in the direction perpendicular to the rolling direction (magnetic flux density 1.T, frequency 50H
Z) is almost the same as that without laser light irradiation.

Note that WL before laser beam irradiation is 1.10 W/kg, and Wc is 2.84 W/k9. In other words, the laser beam irradiation shown in FIG. 1a allows a 10% reduction in WL. In the case of FIG. 1b, WL hardly changes, and Wc becomes 2.04 W/k9, making it possible to significantly reduce Wc by about 28%. In order to obtain such an effect, there are conditions for laser light irradiation.

First, the width d and pitch of the laser beam irradiated portion 12 are
In both cases of Figure 1 a and b, d=0.01~1 side, 1=1~
3. The time width of the laser pulse is lnS ~ 10 hS,
The energy density P is preferably 0.01 to 1000 J/. In addition, when irradiating pulsed laser light, when the irradiated parts are arranged in a chain line shape or dotted line shape, the diameter d in the L direction is 0.01 to 1 skin in Fig. 1a, and the interval a in the irradiation point C direction is 3 sides or less. , preferably one willow or less. In addition, in Fig. 1b, the diameter d in the C direction is 0.01 to 1 skin, and the irradiation point L
The directional distance a is preferably 3 sides or less, preferably 1 side or less. Furthermore, since the purpose of the laser used is to give a shock, a pulsed laser is best. Continuous lasers are less efficient than pulsed lasers because part of the irradiation energy spreads within the plane due to thermal diffusion, resulting in a small energy loss. Even if the directions of the laser irradiated portions 12 in FIGS. 1a and 1b are not aligned exactly perpendicular and parallel to the rolling direction, there will be no particular difference in the effect as long as they deviate within a range of about ±300. do not have. Therefore, in the present invention, each steel plate element constituting the EI or CI core is irradiated with a laser beam as shown in FIG.

The type 1 steel plate element 2 is cut out with its longitudinal direction aligned with the rolling direction of the unidirectional electrical steel plate, and the laser beam irradiation portion 12 is set in the width direction of the type 1 steel plate element 20. In order to create the laser beam irradiation portion 12, the pulsed laser beam may be sequentially deflected, that is, scanned, or the pulsed laser beam may be limited by a slit or the like and a narrow strip of pulsed laser beam that coincides with the portion 12 may be irradiated. In the case of the latter pattern irradiation, a plurality of laser beam irradiation portions 12 may be projected simultaneously. Since the magnetic flux necessarily passes in the direction shown by the dotted line, if this is done, the iron loss will be 4.0 for the reason explained in FIG. 1a. E type steel plate element 22
The longitudinal direction of the three leg parts 22a is set in the rolling direction, and the longitudinal direction of the yoke part 22b is set in the direction perpendicular to the rolling direction (the reverse is also possible), and the laser beam irradiation area 12 is Take it in the width direction. In this way, iron loss is reduced in both the three leg portions 22a for the reason explained in FIG. 1a and the yoke portion 22b for the reason explained in FIG. 1b. The same applies to the C-shaped core 24 shown in FIG. 3b. The corners 22c and 22d are not easily irradiated with laser light. Since the ratio of the corner portion to the entire core is small, this can also sufficiently increase the effectiveness of reducing iron loss. Alternatively, the corners 22c and 22d may be extended directly to the angle bisected by the diagonal line 26 for the laser beam irradiation of the legs and yoke as shown in FIG. 3c. In the T-shaped part 22e of the E-shaped core, the magnetic flux of this part is a → b, when this EI core is used as the iron core of a three-phase transformer.
It passes in the six directions b→c'C→a and the opposite directions. Therefore, it is preferable that this part is essentially non-directional, but when using a grain-oriented electrical steel sheet, the direction shown in Figure 3a is Either the laser beam is not irradiated, or the laser beam irradiation of the yoke part is directly applied to the T-section as shown in FIG. As explained above, according to the present invention, the iron loss of CI and EI cores made of unidirectional electrical steel sheets can be reduced by the simple means of pulsed laser beam irradiation.

As is well known, iron loss occurs constantly during the operation of a transformer, and even a small reduction in iron loss results in extremely large power savings over the entire life of the transformer.Therefore, the present invention is extremely effective from an energy saving perspective. It is.

[Brief explanation of the drawing]

Figures 1a and b are diagrams explaining the procedure for laser light irradiation, Figures 2a and b are diagrams explaining the reason for iron loss improvement, and Figures 3a to b are diagrams explaining the method of irradiation with laser light. It is a figure explaining the laser beam irradiation procedure. In the drawing, 20 is a type 1 core element of CI or EI core, 22
24 is an E-type core element, 24 is a C-type core element, and 12 is a laser beam irradiation portion. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 The CI or EI type core of a transformer is cut from a unidirectional electrical steel sheet with its longitudinal direction aligned with the rolling direction, and the E or C type core is cut with its legs aligned in the longitudinal direction. The I-type steel plate element and the E, C-type steel plate element are cut out from the steel plate in the rolling direction and are irradiated with a laser beam with a predetermined width approximately in the width direction. 1. A method for improving iron loss in a transformer, comprising irradiating pulsed laser light so that the portions extend and are arranged at a predetermined pitch in a direction perpendicular to the width direction.