Patent ID: 12198850

DESCRIPTION OF EMBODIMENTS

A stationary induction apparatus according to embodiments of the present invention will be described below with reference to the drawings. In the following description of embodiments, like or corresponding parts in the drawings are denoted by like reference signs and a description thereof will not be repeated. In the following embodiments, a transformer will be described as a stationary induction apparatus. However, the stationary induction apparatus is not limited to a transformer and may be a reactor or the like.

First Embodiment

FIG.1is a diagram showing a configuration of a stationary induction apparatus according to a first embodiment of the present invention.FIG.2is a partial cross-sectional view of the stationary induction apparatus inFIG.1as viewed from the direction of arrow II-II.

As shown inFIG.1andFIG.2, a stationary induction apparatus100according to the first embodiment of the present invention includes a core110, a winding120, a support130, and a plurality of magnetic shields140. Stationary induction apparatus100includes a high voltage winding121and a low voltage winding122as winding120.

As shown inFIG.1andFIG.2, winding120is wound around core110as the center axis. Specifically, high voltage winding121and low voltage winding122are concentrically wound around a main leg of core110as the center axis. That is, stationary induction apparatus100according to the first embodiment is a shell-type transformer.

Stationary induction apparatus100further includes a tank101. The tank is filled with insulating oil or insulating gas that is an insulating medium and a cooling medium. For example, mineral oil, ester oil, or silicone oil is used as the insulating oil. For example, SF6gas or dry air is used as the insulating gas. Core110, high voltage winding121, and low voltage winding122are accommodated in the tank.

Tank101includes a lower tank and an upper tank arranged above the lower tank. The lower tank has a flange, and the upper tank rests on the flange. The lower tank and the upper tank are welded and formed to be integrated.

High voltage winding121is positioned with respect to low voltage winding122such that high voltage winding121is sandwiched between low voltage windings122in the axial direction X of the center axis.

As shown inFIG.1andFIG.2, support130extends between winding120and core110in the axial direction X of the center axis and supports core110. As shown inFIG.1, support130rests on the flange of tank101on both ends in the axial direction X.

Support130has a shield support surface131positioned on the opposite side to the side closer to core110. On shield support surface131, a plurality of fixing portions132that fix a plurality of magnetic shields140are provided to be spaced apart from each other in the axial direction X.

Support130is formed of a nonmagnetic material. Support130is formed of, for example, nonmagnetic stainless steel. Each of a plurality of fixing portions132is formed of a nonmagnetic material. Each of a plurality of fixing portions132is formed of, for example, stainless steel.

FIG.3is a perspective view showing a plurality of magnetic shields and a plurality of fixing portions in the stationary induction apparatus according to the first embodiment of the present invention.FIG.4is a cross-sectional view showing a plurality of magnetic shields and a plurality of fixing portions shown inFIG.3as viewed from the direction of arrow IV-IV. InFIG.4, support130is also partially shown.

As shown inFIG.1andFIG.2, each of a plurality of magnetic shields140is positioned between winding120and support130on the opposite side to the side closer to core110of support130. As shown inFIG.3, a plurality of magnetic shields140are arranged to be aligned in the axial direction X with a gap141therebetween. Stationary induction apparatus100according to the present embodiment includes three magnetic shields140having an identical configuration. Each of a plurality of magnetic shields140has one end143and the other end144in the axial direction X.

As shown inFIG.1, stationary induction apparatus100according to the first embodiment includes a plurality of other magnetic shields190facing winding120at a different position from that of a plurality of magnetic shields140. The other magnetic shields190are directly bonded to tank101or core110, or bonded to tank101or core110only through fixing portions.

As shown inFIG.2andFIG.3, each of a plurality of magnetic shields140is formed with a plurality of electromagnetic steel plates142stacked in a direction vertical to each of the axial direction X and the normal direction Y to shield support surface131. Each of a plurality of magnetic shields140is formed with electromagnetic steel plates142and thus has a higher permeability compared with support130and each of a plurality of fixing portions132formed of a nonmagnetic material. Leakage flux therefore is easily concentrated on magnetic shield140compared with support130and each of a plurality of fixing portions132.

As shown inFIG.2andFIG.3, in each of a plurality of magnetic shields140, a pair of conductive walls145each having a layer thickness greater than that of electromagnetic steel plate142are stacked on both ends in the stacking direction Z of the electromagnetic steel plates. In the present embodiment, when viewed from the stacking direction Z, the outer shape of each of a pair of conductive walls145is the same as the outer shape of electromagnetic steel plate142.

As shown inFIG.2andFIG.3, in the stacking direction Z of a plurality of electromagnetic steel plates142, each of a plurality of fixing portions132extends across the entire length of each of a plurality of magnetic shields140and fixes a plurality of electromagnetic steel plates142to each other by welding.

As shown inFIG.2toFIG.4, each of a plurality of magnetic shields140is fixed to shield support surface131by at least two fixing portions132aligned in the axial direction X as a plurality of fixing portions132. In the present embodiment, each of a plurality of magnetic shields140is fixed to shield support surface131by two fixing portions132.

As shown inFIG.4, the shortest spacing distance L1between each of a plurality of magnetic shields140and support130is twice or more the length L2of gap141between magnetic shields140adjacent to each other in a plurality of magnetic shields140. The shortest spacing distance L1is, for example, 2 mm or less, and the length of gap141is, for example, 5 mm.

Leakage flux in stationary induction apparatus100according to the present embodiment will now be described. As shown inFIG.1, in the present embodiment, for example, leakage flux B is produced, which passes through between high voltage winding121and low voltage winding122and surrounds high voltage winding121so as not to reach core110. This leakage flux B and the like is incident on a plurality of magnetic shields140to become first leakage flux B1passing through a plurality of magnetic shields140in the axial direction X.

Furthermore, as shown inFIG.2, in the present embodiment, apart from first leakage flux B1, second leakage flux B2passing through between high voltage winding121and low voltage winding122is produced. The magnetic line of second leakage flux B2is annular when viewed from the normal direction Y. Second leakage flux B2is incident on magnetic shield140from the stacking direction Z, for a plurality of magnetic shields140.

As shown inFIG.4, second leakage flux B2produces first eddy current I1that forms an annular path when viewed from the stacking direction Z in electromagnetic steel plate142. Here, since stationary induction apparatus100according to the present embodiment includes a plurality of magnetic shields140as the magnetic shield, the area of the electromagnetic steel plate when viewed from the stacking direction Z is smaller compared with when the magnetic shield is formed with one magnetic shield. Thus, the current path of first eddy current I1produced by second leakage flux B2can be shortened.

Furthermore, as shown inFIG.4, in stationary induction apparatus100according to the first embodiment of the present invention, when first leakage flux B1passes through the gap141, first leakage flux B1partially leaks from electromagnetic steel plate142to the side closer to support130than gap141or the opposite side to the side closer to support130and thereafter is incident on electromagnetic steel plate142again.

Here, since the shortest spacing distance L1is twice or more the length L2of gap141, first leakage flux B1leaking to the side closer to support130than gap141can be suppressed from passing through support130. Accordingly, heating of support130due to passage of first leakage flux B1through support130can be suppressed.

Furthermore, in each a plurality of magnetic shields140and a plurality of fixing portions132, second eddy current is produced, which has a path different from first eddy current I1caused by second leakage flux B2. This second eddy current will be described below.

FIG.5is a diagram schematically showing a path of second eddy current flowing through each of the magnetic shield and the fixing portion in the stationary induction apparatus according to the first embodiment of the present invention.FIG.6is a diagram schematically showing a path of second eddy current when viewed from the stacking direction of electromagnetic steel plates in the stationary induction apparatus according to the first embodiment of the present invention. InFIG.6, the outer shape of magnetic shield140is depicted by dotted lines. InFIG.6, only one of electromagnetic steel plates142included in magnetic shield140is shown.

As shown inFIG.5andFIG.6, second leakage flux B2may sometimes be incident on the magnetic shield from a direction inclined relative to the stacking direction Z. In this case, second eddy current I2is produced, in which both of electromagnetic steel plate142and fixing portion132serve as a current path. Second eddy current I2flows through one of electromagnetic steel plates142included in magnetic shield140along the axial direction X and thereafter flows toward fixing portion132that fixes this electromagnetic steel plate142. Next, as shown inFIG.5, second eddy current I2flows through fixing portion132along the stacking direction Z and thereafter flows through not-shown another electromagnetic steel plate along the axial direction X. Then, second eddy current I2flows through another fixing portion132toward the above-noted electromagnetic steel plate142along the stacking direction Z and thereafter flows into electromagnetic steel plate142again. Second eddy current I2has an annular current path as described above.

In the present embodiment, as shown inFIG.6, the dimension of the length L3between one end143and a side surface132A on the side closer to one end143in fixing portion132positioned closest to one end143of at least two fixing portions132in the axial direction X is greater than the dimension of the height H of each of a plurality of magnetic shields140in the normal direction Y to shield support surface131. Furthermore, the dimension of the length L3between the other end144and a side surface132B on the side closer to the other end144in fixing portion132positioned closest to the other end144of at least two fixing portions132in the axial direction X is greater than the dimension of the height H of each of a plurality of magnetic shields140in the normal direction Y to shield support surface131.

It is preferable that each of a plurality of fixing portions132is arranged as near one end143or the other end144as possible in order to stably fix each of a plurality of electromagnetic steel plates142. However, in the present embodiment, the dimension of the length L3is purposefully greater than the dimension of the height H so that the path of second eddy current I2has a distribution. Specifically, as shown inFIG.6, second eddy current I2has a distribution on each of the outside of fixing portion132positioned closest to one end143in the axial direction X and the outside of fixing portion132positioned closest to the other end144in the axial direction X on electromagnetic steel plate142.

In the present embodiment, since the path of second eddy current I2has a distribution, the heating density of electromagnetic steel plate142by second eddy current I2can be reduced. Thus, local temperature increase in stationary induction apparatus100can be suppressed.

The position of gap141in a plurality of magnetic shields140as a whole in the first embodiment of the present invention will now be described.

As shown inFIG.4, in embodiments of the present invention, in view of shortening the path of first eddy current I1, it is preferable that gaps141are arranged in a plurality of magnetic shields140as a whole such that the area of electromagnetic steel plate142is reduced when viewed from the stacking direction Z. However, if gap141is formed in a place where the magnetic flux density of first leakage flux B1that is the main leakage flux passing through the magnetic shield140is high, first leakage flux B1is more likely to leak from the gap141to support130and the like.

FIG.7is a diagram showing a relative position of the gap with respect to a central position of plurality of magnetic shields as a whole in the axial direction in the stationary induction apparatus according to the first embodiment of the present invention.FIG.8is a graph showing the result of analysis of change in magnetic flux density in the axial direction of first leakage flux passing through a plurality of magnetic shields and the gap between a plurality of magnetic shields in the stationary induction apparatus according to the first embodiment of the present invention. InFIG.8, the center position O of a plurality of magnetic shields140as a whole in the axial direction X is denoted as the origin of coordinates.

As shown inFIG.7andFIG.8, in the present embodiment, the magnetic flux density of first leakage flux B1is highest at the center position O of a plurality of magnetic shields140as a whole. Furthermore, at the position X1of gap141in the axial direction X, gap141is arranged at a position where the magnetic flux density is 0.5 T or less. More specifically, at the position X1of gap141in the axial direction X, gap141is arranged at a position where the magnetic flux density is 0.35 T or less.

In this way, a plurality of magnetic shields140are configured such that the magnetic flux density of a magnetic field passing through gap141between magnetic shields140adjacent to each other in a plurality of magnetic shields140in the axial direction X is 0.5 T or less. It is more preferable that a plurality of magnetic shields140are configured such that the magnetic flux density of a magnetic field passing through gap141in the axial direction X is 0.35 or less.

Here,FIG.8shows the magnetic flux density of first leakage flux B9in a stationary induction apparatus according to a comparative example. The stationary induction apparatus according to the comparative example differs from stationary induction apparatus100according to the first embodiment of the present invention only in that a magnetic shield is formed in an integrated manner. The length in the axial direction X of the magnetic shield in the comparative example is equal to the length in the axial direction X of a plurality of magnetic shields140as a whole in the first embodiment of the present invention.

When the intensity of the magnetic flux density of first leakage flux B1in the present embodiment is compared with the intensity of the magnetic flux density of first leakage flux B9in the comparative example, the tendency of change in magnetic flux density in the axial direction X is substantially the same. This shows that, in the present embodiment, first leakage flux B1is suppressed from leaking from gap141to the side closer to support130than electromagnetic steel plate142or the opposite side to support130.

As described above, stationary induction apparatus100according to the first embodiment of the present invention includes core110, winding120, support130, and a plurality of magnetic shields140. Winding120is wound around core110as the center axis. Support130is formed of a nonmagnetic material and extends between winding120and core110in the axial direction X of the center axis to support core110. Each of a plurality of magnetic shields140is positioned between winding120and support130on the opposite side to the side closer to core110of support130. Support130has shield support surface131positioned on the opposite side to the side closer to core110. On shield support surface131, a plurality of fixing portions132that fix a plurality of magnetic shields140are provided to be spaced apart from each other in the axial direction X. Each of a plurality of fixing portions132is formed of a nonmagnetic material. A plurality of magnetic shields140are arranged to be aligned in the axial direction X with a gap141therebetween. Each of a plurality of magnetic shields140is formed with a plurality of electromagnetic steel plates142stacked in a direction vertical to each of the axial direction X and the normal direction Y to shield support surface131. The shortest spacing distance L1between each of a plurality of magnetic shields140and support130is twice or more the length L2of gap141between magnetic shields140adjacent to each other in a plurality of magnetic shields140.

Thus, the current path of first eddy current I1produced by second leakage flux B2incident on electromagnetic steel plate142in the stacking direction Z of electromagnetic steel plates142can be shortened. Accordingly, heating of electromagnetic steel plates142can be suppressed. Furthermore, in the axial direction X, first leakage flux B1incident on electromagnetic steel plate142can be suppressed from leaking from electromagnetic steel plate142and passing through support130. Accordingly, heating of support130can be suppressed. As described above, temperature increase of stationary induction apparatus100can be suppressed.

In stationary induction apparatus100according to the first embodiment of the present invention, each of a plurality of fixing portions132extends across the entire length of each of a plurality of magnetic shields140in the stacking direction Z of a plurality of electromagnetic steel plates142and fixes a plurality of electromagnetic steel plates142to each other. Each of a plurality of magnetic shields140has one end143and the other end144in the axial direction X. Each of a plurality of magnetic shields140is fixed to shield support surface131by at least two fixing portions132aligned in the axial direction X as a plurality of fixing portions132. The dimension of the length L3between one end143and side surface132A on the side closer to one end143in fixing portion132positioned closest to one end143of at least two fixing portions132in the axial direction X is greater than the dimension of the height H of each of a plurality of magnetic shields140in the normal direction Y to shield support surface131. The dimension of the length between the other end144and side surface132B on the side closer to the other end144in fixing portion132positioned closest to the other end144of at least two fixing portions132in the axial direction X is greater than the dimension of the height of each of a plurality of magnetic shields140in the normal direction Y to shield support surface131.

With this configuration, since the path of second eddy current I2formed by a plurality of electromagnetic steel plates142and a plurality of fixing portions132has a distribution, the heating density of electromagnetic steel plate142by second eddy current I2can be reduced. Consequently, local temperature increase in stationary induction apparatus100can be suppressed.

In stationary induction apparatus100according to the first embodiment of the present invention, a plurality of magnetic shields140are configured such that the magnetic flux density of a magnetic field passing through gap141between magnetic shields140adjacent to each other in a plurality of magnetic shields140in the axial direction X is 0.5 T or less.

This configuration further suppresses first leakage flux B1from leaking from gap141to the side closer to support130than electromagnetic steel plate142or the opposite side to support130and shortens the current path of eddy current by second leakage flux B2.

Second Embodiment

A stationary induction apparatus according to a second embodiment of the present invention will now be described. The stationary induction apparatus according to the second embodiment of the present invention differs from stationary induction apparatus100according to the first embodiment of the present invention in that an insulating member is positioned in the gap, and a configuration similar to the stationary induction apparatus according to the first embodiment of the present invention will not be repeated.

FIG.9is a cross-sectional view showing a partial configuration of the stationary induction apparatus according to the second embodiment of the present invention.FIG.9shows the same cross section as that of stationary induction apparatus100according to the first embodiment of the present invention shown inFIG.4.

As shown inFIG.9, in the present embodiment, an insulating member250is positioned in gap141. Thus, insulating member250is sandwiched between a plurality of magnetic shields140adjacent to each other, whereby the length of gap141can be easily controlled.

Insulating member250has a pawl251for preventing a portion positioned in gap141from dropping. In the present embodiment, pawl251is provided on the opposite side to the side closer to support130of magnetic shield140but may be provided on the side closer to support130of magnetic shield140. Insulating member250does not necessarily have pawl251and may be simply positioned in gap141.

Insulating member250is formed of, for example, a nonmetal material, specifically, formed of pressboard.

In the foregoing embodiments, mutually combinable configurations can be combined as appropriate.

The foregoing embodiments disclosed here are illustrative in all respects and are not intended to provide a basis for limited interpretation. The technical scope of the present invention should not be interpreted only with the foregoing embodiments. All modifications that come within the meaning and range of equivalence to the claims are embraced here.

REFERENCE SIGNS LIST

100stationary induction apparatus,101tank,110core,120winding,121high voltage winding,122low voltage winding,130support,131shield support surface,132fixing portion,132A,132B side surface,140magnetic shield,141gap,142electromagnetic steel plate,143one end,144the other end,145conductive wall,190other magnetic shield,250insulating member,251pawl, B leakage flux, B1, B9first leakage flux, B2second leakage flux, I1first eddy current, I2second eddy current, X axial direction, Y normal direction, Z stacking direction.