JP7492476B2 - Current transformer - Google Patents

Description

The present invention relates to a current transformer. Specifically, the present invention relates to a conductor through-type current transformer.

A conductor-through type current transformer in which the conductor is fixed to the current transformer body is known. For example, the current transformer of Patent Document 1 has a current transformer body having an L-shaped portion with flanges on both sides of a rectangular through hole. A threaded hole is formed in the flange, and the conductor is pressed and fixed into the through hole of the current transformer body by a fixing screw tightened into the threaded hole. Patent Document 1 requires the formation of a flange on the current transformer body. In addition, since the flange, which is part of the current transformer body, is made of an insulating material such as resin, there is a risk that the fixing screw will loosen and fall off due to the difference in expansion coefficient between the steel fixing screw and the resin part.

Utility Model Application Publication No. 2-72602

According to one embodiment of the present invention, it is possible to provide a conductor-through type current transformer in which the conductor can be fixed to the transformer body without risking damage to components.

According to one embodiment of the present invention, there is provided a current transformer comprising a current transformer body having an annular casing, a conductor disposed through a central opening of the annular casing and having at least a pair of threaded holes into which a screw member is screwed, the current transformer further comprising a pair of fixing plates disposed in the central opening, the pair of fixing plates having a rectangular opening into which the conductor is inserted, the pair of fixing plates having an outer surface facing outward from the central opening and an inner surface facing inward from the central opening, the conductor having a protrusion disposed at a position away from the threaded hole in the longitudinal direction of the conductor, the outer surface of the fixing plate including an engagement surface capable of engaging with the head of the screw member, and the inner surface of the fixing plate including an abutment surface capable of abutting against the protrusion.

1 is a perspective view showing an external appearance of a current transformer according to an embodiment of the present invention; FIG. 4 is a perspective view showing the outside of one of the casing halves. FIG. 2B is a perspective view showing the inside of the casing half of FIG. 2A. FIG. 4 is a perspective view showing the outside of the other casing half. FIG. 3B is a perspective view showing the inside of the casing half of FIG. 3A. FIG. 4 is a perspective view showing the outer surface of the fixing plate. FIG. 4 is a perspective view showing the inner surface of the fixing plate. FIG. 13 is a diagram showing a free state of the fixed plate. 11A and 11B are diagrams illustrating a fixed state of a fixing plate. FIG. 11A to 11C are diagrams illustrating a method for fixing a fixing plate to a conductor.

The following describes an embodiment of the present invention with reference to the drawings. Note that the following description is merely an example, and is not intended to limit the technical scope of the present invention to the following embodiment. In the drawings, identical or corresponding components are given the same reference numerals and duplicate descriptions are omitted. In the following description, terms indicating directions such as "upper" and "lower" refer to the directions in the installed state of the current transformer shown in Figure 1.

Figure 1 is a perspective view showing a current transformer 10 according to one embodiment of the present invention. The current transformer 10 comprises a current transformer body (reference numeral omitted) with an annular casing 12, a conductor 14 having a terminal screw hole 70 as a terminal portion, and a pair of fixing plates 16. The annular casing 12 and the fixing plates 16 are formed of an insulating material such as resin. The annular casing 12 houses a coil (not shown) wound around an annular iron core. The current transformer 10 is attached to an appropriate installation surface via a mounting base 18.

The fixed plates 16 are configured such that a pair of fixed plates 16a, 16b are detachably attached to a cylindrical central opening 20 of the annular casing 12. Each fixed plate 16 has a rectangular opening 22 into which the conductor 14 is inserted. For ease of explanation, in FIG. 1, the fixed plates 16a, 16b are shown in a state where they are removed from the annular casing 12. The conductor 14 is placed in the rectangular opening 22 of the fixed plates 16a, 16b so as to pass through the central opening 20 of the annular casing 12. As described below, the fixed plates 16a, 16b can be fixed to the conductor 14, and the fixed plates 16a, 16b and the annular casing 12 can be fixed to each other in the rotational direction.

The annular casing 12 is divided into two casing halves 12a and 12b. The casing halves 12a and 12b are aligned with each other by their respective positioning protrusions 21a and 21b, and are configured to be screwed together at multiple locations (four locations in this embodiment).

The exterior of one casing half 12a (shown on the left side of FIG. 1) is shown in FIG. 2A, and the interior of the casing half 12a is shown in FIG. 2B. The casing half 12a has a coil housing section 24 therein that houses a coil with an iron core (not shown). The casing half 12a also has a fixing section 26 that is screwed to the other casing half 12b shown in FIGS. 3A and 3B. The positioning protrusion 21a is provided on the fixing section 26 at the top of the coil housing section 24. The top of the coil housing section 24 is also configured to accommodate a secondary terminal fitting 28 (see FIG. 1) to which the lead wire of the coil is connected.

2B, the casing half 12a has an outer peripheral wall 30a and an inner peripheral wall 32a that define the coil accommodating section 24. The inner peripheral wall 32a forms a fitting portion that fits with the inner peripheral wall 32b of the other casing half 12b. The outer peripheral wall 30a also forms a fitting portion that fits with the outer peripheral wall 30b of the other casing half 12b. In this embodiment, a groove forming portion is provided on the wall surface of the inner peripheral wall 32a in the central opening 20. The groove forming portion can be composed of, for example, a base portion 34a formed on the cylindrical inner surface of the inner peripheral wall 32a and a groove portion 36a formed in the base portion 34a and extending linearly in the axial direction of the central opening 20.

The outside of the other casing half 12b is shown in FIG. 3A, and the inside of the casing half 12b is shown in FIG. 3B. The casing half 12b has a coil housing 24 therein that houses a coil with an iron core (not shown). The casing half 12b also has a fixing part 26 that is screwed to the casing half 12b. The fixing part 26 at the top of the coil housing 24 is provided with a positioning protrusion 21b that is aligned with the positioning protrusion 21a. The top of the coil housing 24 is also configured to accommodate a secondary terminal fitting 28 (see FIG. 1) to which the lead wire of the coil is connected.

3B, the casing half 12b has an outer peripheral wall 30b and an inner peripheral wall 32b that define the coil accommodating section 24. The inner peripheral wall 32b forms a fitting portion that fits with the inner peripheral wall 32a of the casing half 12a. The outer peripheral wall 30b also forms a fitting portion that fits with the outer peripheral wall 30a of the other casing half 12a. In this embodiment, a groove forming portion is provided on the wall surface of the inner peripheral wall 32b in the central opening 20. The groove forming portion may be composed of, for example, a base portion 34b formed on the cylindrical inner surface of the inner peripheral wall 32b and a groove portion 36b formed in the base portion 34b and extending linearly in the axial direction of the central opening 20. When the casing halves 12a and 12b are fitted together, the groove portion 36b may be connected to the groove portion 36a of the casing half 12a or may be spaced apart from the groove portion 36a in the axial direction.

As shown in Figures 2A and 3A, the outer surfaces of the casing halves 12a and 12b have indicators 38a and 38b for fixing the fixing plates 16a and 16b to the casing halves 12a and 12b at fixed positions, which will be described later.

Figure 4 shows the outer surface 40 of the fixing plates 16a, 16b that are detachably attached to the casing halves 12a, 12b, and Figure 5 shows the inner surface 42 of the fixing plates 16a, 16b. The current transformer 10 has a pair of fixing plates 16a, 16b, which have substantially the same configuration, and therefore will be described here with the common reference numeral 16 for the fixing plates.

In this embodiment, a fixed plate 16 having a circular outer shape is disposed in the cylindrical central opening 20 of the annular casing 12. The fixed plate 16 is disposed so that the outer surface 40 faces the outside of the central opening 20 of the current transformer body, and the inner surface 42 faces the inside of the central opening 20. As shown in FIG. 5, the fixed plate 16 can have a tapered mating surface 44 extending circumferentially between the outer surface 40 and the inner surface 42. Also, as shown in FIG. 2A and FIG. 3A, the casing halves 12a and 12b each have a tapered mating surface 31a and 31b that extends circumferentially along the mating surface 44. Thus, the fixed plate 16 is configured to be mated with the annular casing 12 by the mating surface 44 and the mating surfaces 31a and 31b. As described above, the fixed plate 16 has a rectangular opening 22 for passing the conductor 14.

Referring to FIG. 4, the outer surface 40 of the fixed plate 16 has index portions 46 that can position the fixed plate 16 relative to the casing halves 12a, 12b. The index portions 46 can be aligned with the index portions 38a, 38b of the annular casing 12 described above. As shown in FIG. 5, the fixed plate 16 can also have a protrusion 48 that extends, for example, from the inner surface 42 in the axial direction of the central opening 20. The index portions 46 are provided at positions corresponding to the protrusions 48 in the circumferential direction of the fixed plate 16.

The protrusions 48 can be axially inserted into the grooves 36a, 36b of the casing halves 12a, 12b. However, depending on the specific shapes of the fixing plate 16 and the annular casing 12, the protrusions 48 can also be provided on the mating surface 44. By inserting the protrusions 48 into the grooves 36a, 36b, the fixing plate 16 can be prevented from rotating relative to the annular casing 12.

The fixing plate 16 also has a fixing portion for the conductor 14. Specifically, an engagement surface portion 50 having the form of a protrusion can be provided on the outer surface 40 of the fixing plate 16 adjacent to one long side portion 45 of the rectangular opening 22. The engagement surface portion 50 can include an engagement surface 50a that can engage with the head of a screw member 56, which will be described later. In this embodiment, the engagement surface 50a forms a curved surface that partially surrounds the head of the screw member 56, and is slightly wider on the side away from the rectangular opening 22 (lower in FIG. 4).

The inner surface 42 of the fixing plate 16 may be provided with an abutment surface 52 having the form of a protrusion. The abutment surface 52 may be provided adjacent to the long side 45 of the rectangular opening 22 at a position opposite the engagement surface 50. The abutment surface 52 may include an abutment surface 52a that can abut against a protrusion 60 of the conductor 14 described below. In this embodiment, the abutment surface 52a forms a curved surface that partially surrounds the protrusion 60.

Next, a method of fixing the fixing plate 16 to the casing halves 12a, 12b will be described with reference to Figures 6 and 7. Here, the casing half 12b is illustrated, but substantially the same fixing method is also applied to the casing half 12a. Figure 6 shows the state in which the fixing plate 16 is fitted and arranged in the casing half 12b (substantially only the inner peripheral wall 32b is illustrated). In the state of Figure 6, the protrusion 48 of the fixing plate 16 is not received in the groove 36b of the casing half 12b, so the fixing plate 16 can rotate with respect to the casing half 12b.

The projection 48 can be axially inserted into the groove 36b at a position where the index portion 46 of the fixing plate 16 and the index portion 38b of the casing half 12b are aligned with each other. This allows the fixing plate 16 to be attached to the casing half 12b at a fixed position where the fixing plate 16 cannot rotate relative to the casing half 12b. Figure 7 shows the positional relationship between the projection 48 and the groove 36b when the fixing plate 16 is in the fixed position. However, the fixing plate 16 does not necessarily have to be attached in a fixed position. Therefore, the fixing plate 16 may be held in a free state, for example as shown in Figure 6, where the fixing plate 16 can rotate relative to the casing half 12b.

When assembling the current transformer 10, some workers find it easier to rotate the fixed plate 16 to some extent. Therefore, the fixed plate 16 may be selectively placed in a fixed or free state depending on the preference of each individual worker. When changing the fixed plate 16 from a fixed state to a free state or from a free state to a fixed state, the fixed plate 16 can be separated from the casing halves 12a and 12b, rotated to the desired position, and then re-fitted into the casing halves 12a and 12b.

Figure 8 shows the conductor 14 alone. The conductor 14 has a fixing portion for the fixing plate 16. Specifically, the conductor 14 can have threaded holes 58 configured to screw in the screw members 56 (see Figure 9) on both sides of the planar portion 54 in the longitudinal direction, and, for example, protrusions 60. In the illustrated example, two protrusions 60 are provided on each side of the conductor 14 in the longitudinal direction, but the number of protrusions 60 is not particularly limited. In addition, the specific shape of the protrusions 60 is not limited to that shown in the figure. The fixing plate 16 is disposed between the protrusions 60 on each side and the threaded holes 58. Therefore, the distance between the threaded holes 58 and the protrusions 60 on each side is determined according to the thickness of the fixing plate 16. The protrusions 60 can be formed, for example, by extruding a portion of the conductor 14.

Next, a method for fixing the fixing plate 16 to the conductor 14 will be described with reference to FIG. 9. The annular casing 12 is omitted from FIG. 9. The arrangement of the annular casing 12 can be seen, for example, in FIG. 1. Note that the flat surface 54 of the conductor 14 shown in FIG. 9 is located on the underside of the conductor 14 in FIG. 1.

The fixing plate 16 is positioned between the threaded hole 58 and the protrusion 60 of the conductor 14 with the outer surface 40 facing outward from the central opening 20 of the annular casing 12 and the inner surface 42 facing inward from the central opening 20 of the annular casing 12.

When the screw member 56 is screwed into the threaded hole 58, the head of the screw member 56 engages with the engagement surface 50a of the engagement surface portion 50, and the engagement surface 50a is pressed in the length direction of the conductor 14 by the head of the screw member 56. As a result, the abutment surface 52a of the abutment surface portion 52 provided on the inner surface 42 of the fixing plate 16 abuts against the convex portion 60 of the conductor 14. In this way, the fixing plate 16 is clamped between the convex portion 60 and the head of the screw member 56.

Therefore, for example, when assembling the current transformer 10 as shown in FIG. 1, the conductor 14 is placed in the central opening 20 of the assembled annular casing 12, and the fixing plate 16a, for example, is fixed to the conductor 14 on one side of the conductor 14 in the manner described above.

Next, the fixing plate 16a to which the conductor 14 is fixed is fitted to one of the casing halves of the annular casing 12, for example the casing half 12a, via the fitting surfaces 31a and 44. At this time, when the fixing plate 16a and the casing half 12a are fitted together at a position where the index portion 38a and the index portion 46 are aligned, the protrusion 48 of the fixing plate 16a can be inserted axially into the groove portion 36a of the casing half 12a. This fixes the fixing plate 16 in the rotational direction relative to the casing half 12a. However, as described above, the fixing plate 16 does not necessarily have to be fixed in the rotational direction to the casing half 12a.

Next, the fixing plate 16b is fixed to the side of the conductor 14 that protrudes outward from the casing half 12b in the same manner as described above. When the fixing of the fixing plate 16b is completed (i.e., when the screw members 56 are tightened on both sides of the annular casing 12), the fixing plates 16a, 16b are fitted to the casing halves 12a, 12b, respectively. The fitting surfaces 31a, 31b of the annular casing 12 can act as stoppers against the axial movement of the fixing plates 16a, 16b.

Thus, according to one embodiment of the present invention, a compact conductor through-type current transformer 10 can be realized in which the fixing plate 16 is fitted into the central opening 20 of the annular casing 12. Conductors 14 of various thicknesses can be fixed to the fixing plate 16 as long as they can be inserted into the rectangular opening 22. In addition, the screw member 56 for fixing is directly fastened to the conductor 14 without going through a part made of resin or the like, and is configured to press the resin fixing plate 16 with the side of the head of the screw member 56. Therefore, there is no risk of the fixing screw loosening as in the prior art. Specifically, by fastening the screw member 56, for example made of brass, to the copper primary conductor 14, the risk of the fixing screw loosening due to thermal expansion can be eliminated.

Although the embodiment of the present invention has been described above, the embodiment of the invention described above is intended to facilitate understanding of the present invention and does not limit the present invention. The present invention may be modified or improved without departing from its spirit, and the present invention naturally includes equivalents. Furthermore, any combination or omission of each component described in the claims and specification is possible within the scope of solving at least part of the above-mentioned problems or achieving at least part of the effects.

For example, in the above embodiment, the protrusion 48 is formed on the fixing plate 16, and the grooves 36a, 36b that receive the protrusion 48 are formed on the casing halves 12a, 12b. However, in other embodiments, the grooves may be formed on the fixing plate 16, and the protrusions that are received in the grooves may be formed on the casing halves 12a, 12b.

The specific shapes, positions, and numbers of the engagement surface portion 50, engagement surface 50a, abutment surface portion 52, and abutment surface 52a of the fixed plate 16 may be changed. In the above embodiment, the engagement surface 50a and abutment surface 52a have the form of a curved surface formed on the protruding engagement surface portion 50 and abutment surface portion 52, respectively, but in other embodiments, the protruding engagement surface portion 50 and abutment surface portion 52 may not be provided. In other words, the engagement surface 50a and abutment surface 52a may be flat surfaces included in the flat outer surface 40 and inner surface 42 of the fixed plate 16, respectively. The fixed plate 16 may be supported by the mating surfaces 31a and 31b of the casing halves 12a and 12b instead of the protruding portion 60 of the conductor 14, in which case the protruding portion 60, abutment surface portion 52, and abutment surface 52b may be omitted.

Also, two or more screw members 56 may be used, and two or more threaded holes 58 may be provided, depending on the number of screw members 56.

The present invention includes the following aspects.
1. A current transformer body having an annular casing;
a conductor disposed through the central opening of the annular casing and having at least a pair of threaded holes into which the screw members are threaded;
A current transformer comprising:
a pair of fixing plates disposed in the central opening, the pair of fixing plates having a rectangular opening into which a conductor is inserted, the pair of fixing plates having an outer surface facing outward from the central opening and an inner surface facing inward from the central opening;
the conductor has a protrusion disposed at a position spaced apart from the threaded hole in a longitudinal direction of the conductor;
the outer surface of the fixation plate includes an engagement surface engageable with a head of the screw member;
The inner surface of the fixing plate includes a contact surface that can contact the protrusion.
Current transformer.
2. The current transformer according to 1. above,
The annular casing has a substantially cylindrical central opening, and the stationary plate has a substantially circular outer shape;
The current transformer has a fixing portion that fixes the fixing plate relative to the annular casing in a rotational direction.
3. The current transformer according to 2. above,
The fixed part is
a protrusion provided on one of the fixed plate and the annular casing and extending in an axial direction of the current transformer;
a groove provided on the other of the fixed plate and the annular casing, the groove being capable of receiving the protrusion in the axial direction.
4. The current transformer according to 2. or 3. above,
A current transformer, wherein an indicator portion indicating the position of the fixing portion is provided on the outer surface of the annular casing and the outer surface of the fixing plate.

The present invention can be widely applied to conductor through-type current transformers.

10 Current transformer 12 Annular casing 14 Conductor 16, 16a, 16b Fixing plate 18 Mounting base 20 Central opening 22 Rectangular opening 12a, 12b Casing half 21a, 21b Positioning protrusion 24 Coil accommodating portion 26 Fixing portion 28 Terminal fitting 30a, 30b Outer wall 31a, 31b Fitting surface 32a, 32b Inner wall 34a, 34b Base 36a, 36b Groove 38a, 38b Index portion 40 Outer surface 42 Inner surface 44 Fitting surface 45 Long side portion 46 Index portion 48 Protrusion 50 Engagement surface portion 50a Engagement surface 52 Abutment surface portion 52a Abutment surface 54 Planar portion 56 Screw member 58 Threaded hole 60 Convex portion 70 Terminal screw hole

Claims (4)

A current transformer body having an annular casing;
a conductor disposed through the central opening of the annular casing and having at least a pair of threaded holes into which a screw member is threaded;
A current transformer comprising:
a pair of fixing plates having a rectangular opening into which the conductor is inserted and disposed in the central opening, the pair of fixing plates having an outer surface facing outward from the central opening and an inner surface facing inward from the central opening;
the conductor has a protrusion disposed at a position spaced apart from the threaded hole in a longitudinal direction of the conductor;
the outer surface of the fixation plate includes an engagement surface engageable with a head of the screw member;
The inner surface of the fixing plate includes a contact surface capable of contacting the protrusion.
Current transformer. 2. A current transformer according to claim 1,
the annular casing having a substantially cylindrical central opening, the stationary plate having a substantially circular outer shape;
The current transformer has a fixing portion that fixes the fixing plate to the annular casing in a rotational direction. 3. A current transformer according to claim 2,
The fixing portion is
a protrusion provided on one of the fixing plate and the annular casing and extending in an axial direction of the current transformer;
a groove portion provided on the other of the fixed plate and the annular casing, the groove portion being capable of axially receiving the protrusion. A current transformer according to claim 2 or 3,
A current transformer, wherein an indicator portion indicating a position of the fixing portion is provided on an outer surface of the annular casing and an outer surface of the fixing plate.

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