JP2001307932A - Core type three-phase transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable magnetic shields provided on the inner surface of the tank of a core type three-phase transformer to be lessened in number so as to reduce the three-phase transformer in weight and cost. SOLUTION: A magnetic shield mounted on the inner surface of a tank confronting a coil is constituted in a manner in which magnetic steel plates each cut into a rectangular shape are laminated into shield blocks, and the shield blocks are arranged in parallel on the inner surface of the tank. The shield blocks arranged on the inner surface of the tank, confronting a central phase coil are set smaller in arrangement density than those arranged confronting edge phase coils.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core-type three-phase transformer housed in a tank.

[0002]

2. Description of the Related Art FIG. 10 is a perspective view showing a general structure of a core-type three-phase transformer housed in a tank. In the figure, 1 is a three-phase leg arranged in an upright state in parallel, and the upper and lower portions of each leg are cored by a yoke, and 2 is wound around each leg of the core 1. A low-voltage coil 2a is disposed on the inner side, and a high-voltage coil 2b is disposed on the outer peripheral side. Numeral 3 clamps and supports the lower part of the iron core 1,
4 is an upper end frame for clamping the upper part of the iron core 1, 5 is a tank containing the iron core 1 and the coil 2, 6
Is a magnetic shield attached to the inner surface of the tank 5. The inside of the tank 5 is filled with an insulating medium such as insulating oil. The magnetic shield 6 is formed by cutting a magnetic steel plate such as a silicon steel plate into a strip shape and laminating the magnetic shield 6 to a predetermined thickness, and is arranged in parallel in the vertical direction on the inner surface of the tank 5.

[0003] In the operating state of the core-type three-phase transformer configured as described above, a leakage magnetic flux is generated around the coil 2 by a load current flowing through the coil 2. If the magnetic shield 6 is not attached to a large-capacity device or a high-impedance device, leakage magnetic flux may pass through the wall of the tank 5, increasing the loss due to overcurrent and increasing the temperature due to local overheating. is there. When the magnetic shield 6 is attached to the inner surface of the tank 5, the leakage magnetic flux is converged on the magnetic shield and does not pass through the wall of the tank 5, so that local overheating does not occur.

[0004] For example, Japanese Patent Laid-Open Publication No. 57-208116 discloses a state in which the magnetic shield 6 is cut into a strip shape and laminated as shown in FIG. As shown in FIG. 12, the shield 6a at the portion facing the coil 2 has a lower stacking height, and the shields 6b on both sides thereof have a higher stacking height to disperse the leakage magnetic flux on both sides. So that the insulation distance between the tank 5 and the inner surface of the tank 5 can be secured.
It is disclosed to reduce the size of the.

Japanese Unexamined Patent Publication (Kokai) No. 62-73703 discloses a shield unit 6 as shown in FIG.
A configuration is shown in which a magnetic shield having a shape in which the thickness of both ends in the longitudinal direction of n is smaller than that of the middle portion is attached, and the weight of the magnetic shield 6 is reduced.

[0006]

The method of arranging the magnetic shields in the above-mentioned conventional core-type transformer is based on the following method.
However, in the case of a three-phase transformer, the leakage magnetic flux generated by the coil 2 of each phase interferes with the adjacent phases and causes the vicinity of the central phase and the end phase. The distribution state of the leakage magnetic flux is different from that near, but the magnetic shield is installed according to the part where the leakage magnetic flux is maximum, and the excess transformer is partially used for the transformer as a whole, and the weight is heavy However, there is a problem that the cost becomes high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a magnetic shield having a cross-sectional area for converging leakage magnetic flux of each phase is arranged as a three-phase transformer, thereby reducing the amount of magnetic shield used. To reduce costs.

[0008]

According to a first aspect of the present invention, there is provided a core-type three-phase transformer, wherein a magnetic shield attached to an inner surface of the tank opposite to the coil is formed by cutting a plurality of magnetic steel sheets into strips and laminating them. The shield blocks are arranged in parallel on the tank inner surface, and the density of the shield blocks placed on the tank inner surface facing the center phase coil is higher than the density of the shield blocks placed on the inner surface facing the end phase coil. Is also smaller.

In a core-type three-phase transformer according to a second aspect of the present invention, the plurality of shield blocks forming the magnetic shield according to the first aspect have the same cutting dimensions and the same stacking height, and have the same phase. The arrangement interval of the shield blocks arranged on the inner surface of the tank facing the coil is wider than the arrangement interval of the shield blocks arranged on the inner surface of the tank facing the coil of the end phase.

According to a third aspect of the present invention, there is provided a core-type three-phase transformer, wherein the plurality of shield blocks forming the magnetic shield according to the first aspect are arranged such that blocks having the same cutting dimensions are arranged at equal intervals, and The stacking height of the shield blocks arranged on the tank inner surface facing the phase coil is lower than the stacking height of the shield blocks arranged on the tank inner surface facing the end phase coil.

According to a fourth aspect of the present invention, there is provided the core-type three-phase transformer according to the second or third aspect, wherein the plurality of shield blocks forming the magnetic shield have a stacked height of an upper end portion and a lower end portion. Are respectively lower than the middle part.

According to a fifth aspect of the present invention, there is provided a core-type three-phase transformer according to the first aspect, wherein a plurality of shield blocks forming a magnetic shield are arranged at equal intervals on an inner surface facing each phase coil. The length of the shield block disposed on the inner surface of the tank facing the coil of the center phase is shorter than the length of the shield block disposed on the inner surface facing the coil of the end phase.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 First, the state of the leakage magnetic flux in the tank portion of the core-type three-phase transformer according to the present invention will be clarified. The structure of the target core-type three-phase transformer is the same as the configuration shown in FIG. FIG. 1 is an explanatory diagram of a calculation model of a leakage magnetic flux. The center of the three-phase coil arrangement direction of the core-type three-phase transformer of FIG. 10 and the coils of each phase (U-phase, V-phase, and W-phase) are illustrated. FIG. 4 is a cross-sectional view below the intermediate position. Figure 2 is a diagram showing an inner surface of the tank 5 opposite to the coil 2 of the lower half of the tank 5 FIG 1, X ₁ -X
₂ is an inner surface of the tank 5 facing an intermediate position in the arrangement direction of each phase of the coil 2, and U ₁ -U ₂ and W ₁ -W ₂ are end phases (U
Phase, W phase) at a position facing the center of the coil, V ₁ −
V ₂ is a position facing the center of the center phase (V phase) coil.

Since the leakage magnetic flux of the coils in which the three phases are arranged in parallel is distributed symmetrically with respect to the center line in the arrangement direction of each phase coil, the current flowing through each phase coil is reduced to 1/4 as shown in FIG. FIGS. 3 and 4 show the results of obtaining the leakage magnetic flux distribution as the current at full load. Figure 3 is a leakage magnetic flux density distribution of X ₁ -X ₂ line in the lateral direction of the tank inner surface which faces the alignment direction of the intermediate position of each phase coil, the horizontal axis is the scale was 1 tank full width. FIG. 4 shows the leakage magnetic flux distribution on the inner surface of the tank 5 facing the central axis of each phase coil. The horizontal axis is a scale with the lower end of the tank 5 being 0 and the middle position of the coil being 1. The vertical axis of FIGS. 3 and 4 is a leakage magnetic flux density ratio indicating the ratio of the leakage magnetic flux density.

In FIG. 3, the leakage magnetic flux distribution between X _{1 and} X ₂ facing the middle position of each phase coil on the inner surface of the tank is the maximum position at the middle position facing the center axis of each phase coil, and the ends of both ends are shown. The portion facing the phase (U phase, W phase) coil has a high leakage magnetic flux density, and the portion facing the center phase (V phase) coil is about 0.75 times the portion facing the end phase coil. . As shown in FIG. 4, the leakage magnetic flux density at a position lower than the lower end of the coil above the lower end frame 3 is low,
The leakage magnetic flux density of each phase is 0.5 times or less the vicinity of the coil center, which is the maximum portion.

When the leakage magnetic flux density distributed as shown in FIGS. 3 and 4 passes through the wall of the tank 5, an eddy current loss occurs in proportion to the square of the passing magnetic flux, and the temperature rises. In order to prevent the leakage magnetic flux from passing through the wall of the tank 5, it can be prevented by disposing a magnetic shield having a cross-sectional area for converging the leakage magnetic flux of each portion on the inner surface of the tank.

FIG. 5 shows an arrangement state of the magnetic shield according to the first embodiment. FIG. 5 shows the inner surface of the lower half of the tank 5 below the intermediate position of the coil. In the figure, 1
6a is a magnetic steel sheet such as a silicon steel sheet having a required length L and a tank 5;
This is a shield unit that is cut into strips of a width that can be easily attached to the inner surface of the unit, and laminated to an appropriate laminated thickness. 16U is a portion facing the end phase (U phase) coil, 16V is a portion facing the center phase (V phase) coil, and 16W is an end phase (W phase).
A magnetic shield placed on the part facing the coil,
A plurality of shield units 16a are arranged in parallel on the inner surface of the portion facing each phase. Pa is an arrangement interval of the U-phase and W-phase shield units 16a, and Pb is an arrangement interval of the V-phase shield units 16a.

Each phase magnetic shield 16U, 16V, 16
The number of the shield units 16a constituting W is determined by selecting the number formed in the cross-sectional area for converging the leakage magnetic flux density at the full load in each phase coil shown in FIGS. The arrangement interval Pb of the center phase (V phase) is determined to be 1.1 of the arrangement interval Pa of the end phases (U phase, W phase) based on the distribution magnetic flux density distribution shown in FIGS. 2
Up to 1.3 times.

In this way, the number of the shield units 16a is selected and determined so that the magnetic shield attached to the inner surface of the tank in the core-type three-phase transformer has a cross-sectional area that converges the leakage magnetic flux of each phase at full load. When placed, the end phase (U
Phase, W phase), the number of shield units in the central phase (V phase) is smaller than the number of shield units 16a to be attached to the magnetic shield, compared to the conventional case where each phase is mounted in the same manner. Use less,
Cost can be reduced.

Embodiment 2 FIG. 6 shows an arrangement state of the magnetic shield according to the second embodiment. In the second embodiment, the shield units constituting the magnetic shield attached to the inner surface of the tank facing each phase coil of the core type transformer are arranged at equal intervals, and the leakage flux of the portion facing each phase coil at full load In which the stacking height is adjusted so that the cross-sectional area converges. FIG. 6 shows the inner surface of the lower half of the tank 5 below the intermediate position of the coil similarly to FIG.

In the figure, 26a is an end phase (U phase, W phase)
A shield unit arranged at a portion facing the coil, 2
Reference numeral 6b denotes a shield unit arranged at a portion facing the center-phase (V-phase) coil. Shield unit 26a, 2
6b cuts a magnetic steel plate such as a silicon steel plate into strips having an appropriate width and a required length, 26a has a stacking height of Ta, and 26b has a stacking height of Tb. 26U is a portion facing the end-phase (U-phase) coil, 26V is a portion facing the center-phase (V-phase) coil, 26W is a magnetic shield of a portion facing the end-phase (W-phase) coil, and a shield unit 26a , 26
b are arranged in parallel with uniform arrangement intervals, and the stacking height Ta of the shield unit 26a and the stacking height Tb of the shield unit 26b, which are cross-sectional areas for converging the leakage magnetic flux of each phase at full load.

Each phase magnetic shield 26U, 26V, 26
The shield units 26a and 26b constituting the W are arranged at equal intervals, and the lamination height T, which is a cross-sectional area for converging the leakage magnetic flux at the time of full load on the inner surface of the tank facing each phase coil.
a, Tb, the stack height Tb of the center-phase (V-phase) shield unit 26b is about 0.7 to 0.8 times the stack height Ta of the end phases (U-phase, W-phase). As compared with the case where each phase is similarly attached, the amount of use of the magnetic shield is reduced, and the cost can be reduced.

Embodiment 3 FIG. FIG. 7 shows an arrangement state of the magnetic shield according to the third embodiment. The third embodiment has a configuration in which the stacked height of both ends of a shield unit constituting a magnetic shield attached to the inner surface of a tank facing a coil is reduced. FIG. 7 shows the inner surface of the lower half of the tank 5 below the intermediate position of the coil similarly to FIG. FIG. 8 is a dimensional view of the shield unit.

In the figure, 36a is an end phase (U phase, W phase)
And a shield unit 36b of a central phase (V phase). 36U is a magnetic shield of a portion facing the end phase (U phase) coil, and 36V is a central phase (V phase).
36W is a magnetic shield of a portion facing the end-phase (W-phase) coil, and 36W is a magnetic shield of a portion facing the end-phase (W-phase) coil. Shield units 36b are arranged in parallel at equal intervals in portions facing the center phase (V phase) coil.

FIG. 8A shows the shield unit 36a.
As shown in FIG. 8 (b), the
The stacking height at both ends is set lower than the stacking height.
The shield units 36a and 36b have a total length of the middle part.
Length L about 1/2 of L₁ Lamination height Ta₁ , T
b₁ Converges the leakage flux of each phase coil at full load
This is the height of the stack, which is the cross-sectional area. Actually, the central phase (V phase)
Stack height Tb ₁ Is the end phase (U phase, W phase)
Lamination thickness Ta₁ Is thinner than Magnetic leakage at both ends
Since the bundle density is small, it is about 1/4 of the total length L
Length L_Two Laminated height Ta at both ends of_Two , Tb_Two The middle part
Of each layer thickness Ta₁ , Tb₁ About 0.5 times
This is the stack height.

Magnetic shields 36U, 36V, 36 of each phase
W central phase of the intermediate portion of the shield units 36b of the (V-phase) stack height Tb ₁ of the (L ₁ portion), end phase (V-phase, W-phase)
Of a 0.7 to 0.8 times the stack height Ta ₁ of the intermediate portion of the shield unit 36a, the end stack height Tb ₁ of the (L ₂ portion), Tb ₂ is the intermediate part stack height Ta ₁ and Tb _1, each having a stacking height of about 0.5 times that of the first embodiment.
Alternatively, the weight can be further reduced as compared with the case of the second embodiment, and the cost can be reduced.

Embodiment 4 FIG. 9 shows an arrangement state of the magnetic shield according to the fourth embodiment. Embodiment 4 is a configuration in which the length of the shield unit constituting the magnetic shield of the central phase attached to the inner surface of the tank facing the coil of the core type transformer is shortened in accordance with the leakage magnetic flux density at full load. It is. FIG. 8 is a cross-sectional view below the intermediate position of the coil as in FIG.

In the figure, 46a is an end phase (U phase, W phase)
Reference numeral 46b denotes a shield unit disposed at a portion facing the coil, and a shield unit 46b is disposed at a portion facing the center-phase (V-phase) coil. Shield unit 46
The length Lb of b is set to about 0.6 times the length La of the shield unit 46a.

46U is a magnetic shield at a portion facing the end-phase (U-phase) coil, 46V is a magnetic shield at a portion facing the center-phase (V-phase) coil, and 46W is a portion facing the end-phase (W-phase) coil. The magnetic shields 46U and 46W facing the U-phase and W-phase coils are configured by arranging shield units 46a and 46V and shield units 46b in parallel at equal intervals, respectively.

In this configuration, the length Lb of the shield unit 46b of the magnetic shield 46V of the center phase is made shorter than that of the end phase in accordance with the leakage magnetic flux density at the time of full load.
The amount of the magnetic shield used is smaller than in the case where the conventional phases are similarly mounted, and the cost can be reduced.

[0031]

According to a first aspect of the present invention, there is provided a core-type three-phase transformer comprising: a plurality of shield blocks formed by cutting a magnetic steel plate into strips and laminating a magnetic shield attached to an inner surface of the tank facing the coil; The arrangement density of the shield blocks arranged on the inner surface of the tank facing the coil of the central phase is smaller than the density of the shield blocks arranged on the inner surface facing the coil of the end phase. In addition, compared with the case where each phase is attached in the same manner, the amount of use of the magnetic shield is reduced, and the cost can be reduced.

In a core type three-phase transformer according to a second aspect of the present invention, the plurality of shield blocks forming the magnetic shield according to the first aspect have the same cutting dimensions and the same stacking height, and the central phase has the same height. The spacing between the shield blocks placed on the inner surface of the tank facing the coil is wider than the spacing between the shield blocks placed on the inner surface of the tank facing the coil in the end phase. As compared with the case where the magnetic shield is used, the use amount of the magnetic shield is reduced, and the cost can be reduced.

In the core-type three-phase transformer according to the third aspect of the present invention, the plurality of shield blocks forming the magnetic shield according to the first aspect are arranged such that blocks having the same cutting dimensions are arranged at equal intervals, and The stacking height of the shield block placed on the tank inner surface facing the phase coil is lower than the stacking height of the shield block placed on the tank inner surface facing the end phase coil, and is the same for each phase. The amount of use of the magnetic shield is reduced as compared with the case where the magnetic shield is mounted as described above, and cost can be reduced.

According to a fourth aspect of the present invention, there is provided the core-type three-phase transformer according to the second or third aspect of the present invention, wherein each shield block of the magnetic shield has an upper end portion and a lower end stacked at an intermediate position. Since the height of the magnetic shield is lower than the stack height, the amount of the magnetic shield used is further reduced, and the weight and cost can be reduced.

In the core-type three-phase transformer according to claim 5 of the present invention, the plurality of shield blocks forming the magnetic shield according to claim 1 are arranged at equal intervals on the inner surface facing each phase coil. The length of the shield block located on the inner surface of the tank facing the center-phase coil is shorter than the length of the shield block located on the inner surface facing the end-phase coil. , The weight can be reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a leakage magnetic flux calculation model of a core-type three-phase transformer.

FIG. 2 is an explanatory diagram of calculation positions of a leakage magnetic flux calculation model of FIG.

FIG. 3 is a distribution diagram of a leakage magnetic flux density at a coil intermediate position on a tank inner surface facing a coil of each phase.

FIG. 4 is a distribution diagram of a leakage magnetic flux density in an axial direction on an inner surface of a tank facing a coil of each phase.

FIG. 5 is a layout diagram of a magnetic shield according to the first embodiment.

FIG. 6 is a layout diagram of a magnetic shield according to a second embodiment.

FIG. 7 is a layout diagram of a magnetic shield according to a third embodiment.

FIG. 8 is a view showing a shape of the shield unit of FIG. 8;

FIG. 9 is a layout diagram of a magnetic shield according to a fourth embodiment.

FIG. 10 is a configuration diagram of a core-type three-phase transformer.

FIG. 11 is a diagram showing a mounting state of a magnetic shield of a conventional core-type three-phase transformer.

FIG. 12 is a partially enlarged view of a magnetic shield part of FIG. 11;

FIG. 13 is a view showing a shape of a magnetic shield attached to a tank of a conventional core-type transformer.

[Explanation of symbols]

16a shield unit, 16U, 16V, 16W
Magnetic shield, 26a Shield unit, 26U, 2
6V, 26W magnetic shield, 36a shield unit, 36b shield unit, 36U, 36V, 36
W Magnetic shield, 46a Shield unit, 46b
Shield unit, 46U, 46V, 46W magnetic shield.

Claims (5)

[Claims] 1. A main body of a three-phase transformer comprising a core having three-phase legs arranged in a line in an upright state and a coil wound around the three-phase legs is housed in a tank. In a core-type three-phase transformer in which a magnetic shield is arranged on the tank inner surface facing the coil, the magnetic shield is formed by cutting a magnetic steel sheet into strips and laminating a plurality of shield blocks in parallel on the tank inner surface. The arrangement density of the shield blocks formed and arranged on the tank inner surface facing the coil of the central phase is as follows:
An inner iron-type three-phase transformer, wherein the density of the shield blocks arranged on the inner surface of the tank facing the coil of the end phase is smaller than the density of the shield blocks. 2. A plurality of shield blocks forming a magnetic shield have the same cutting dimensions and the same stacking height, and the arrangement intervals of the shield blocks arranged on the inner surface facing the central phase coil are opposite to the end phase coil. An inner iron-type three-phase transformer characterized by being wider than an arrangement interval of shield blocks arranged on an inner surface. 3. A plurality of shield blocks forming a magnetic shield, blocks having the same cutting dimensions are arranged at equal intervals, and the stacking height of the shield blocks arranged on the inner surface facing the coil of the central phase is an end phase. An inner iron-type three-phase transformer characterized in that the height is lower than the stacking height of the shield block disposed on the inner surface facing the coil. 4. The inner iron type according to claim 2, wherein the plurality of shield blocks forming the magnetic shield have lower lamination heights at an upper end portion and a lower end portion than at an intermediate portion. Three-phase transformer. 5. A plurality of shield blocks forming a magnetic shield are arranged at equal intervals on the inner surface facing each phase coil, and the length of the shield block arranged on the inner surface of the tank facing the central phase coil is: The inner iron type three-phase transformer according to claim 1, wherein a length of the shield block is shorter than a length of a shield block disposed on an inner surface of the tank facing the end-phase coil.