Manufacturing method of split-type zero-phase current transformer and split-type zero-phase current transformer

Abstract

To obtain stable characteristics without deteriorating zero phase current characteristics by suppressing distortion of a plurality of layers of iron cores due to curing shrinkage stress of an insulating resin.SOLUTION: Disclosed is a method of manufacturing a split type zero phase current transformer which includes the steps of: housing and fixing a work in process 130, in which a secondary coil 15 is wound around a plurality of layers of semi-annular iron cores 13, in a mold 23; and obtaining a second work in process in which the iron core 13, a secondary coil 15, and a spacer 19 are covered with a thermosetting resin by arranging the spacer 19 between the center part in the circumferential direction of the inner peripheral surface of the work in process 130 and the mold 23, and then casting and curing the thermosetting resin in the mold 23.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a split-type zero-phase current transformer for detecting zero-phase current, and to the split-type zero-phase current transformer. [Background technology]

[0002] Electric power receiving equipment is generally equipped with earth fault directional relays for the purpose of earth fault protection, and zero-phase current transformers are widely used to detect earth faults in such earth fault directional relays. Split-type zero-phase current transformers use a combination of semi-annular cores, each formed by dividing an annular core equally into two, with the primary conductors of U, V, and W phases inserted inside the annular core. Zero-phase current transformers output a secondary current corresponding to the vector sum of the currents flowing through these primary conductors as a zero-phase current from their secondary coil. Earth fault directional relays detect leakage currents based on the zero-phase current output from the zero-phase current transformer.

[0003] Split-type zero-phase current transformers are manufactured by fixing the split surface of a semi-annular core, to which the secondary coil and other components are attached, in a mold, pouring insulating resin into the mold, and then covering it with a mold coating. When the insulating resin is poured and hardened in this way, the semi-annular core fixed in the mold is subjected to hardening contraction stress of the insulating resin, causing distortion in the core and deteriorating the zero-phase current characteristics. Zero-phase current transformers are required to have zero-phase current characteristics that do not cause malfunction over a wide range, from low current to overcurrent.

[0004] Patent Document 1 discloses a core configuration that uses a multi-layer annular core that combines permalloy, a highly magnetic material, with silicon steel sheets, which are electromagnetic steel sheets, thereby achieving good error characteristics over a wide current range. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. 173814 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of split-type zero-phase current transformers, the casting method described above means that the hardening shrinkage stress of the insulating resin has a large effect on the iron core. For this reason, if the semi-annular iron core is made up of multiple layers, its mechanical strength against bending stress decreases compared to a single layer, so measures to suppress distortion of the iron core are necessary.

[0007] The present disclosure has been made in consideration of the above, and aims to provide a method for manufacturing a split-type zero-phase current transformer that suppresses distortion of a multi-layered iron core due to hardening shrinkage stress of an insulating resin, and that achieves stable characteristics without deteriorating the zero-phase current characteristics. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the objectives, the manufacturing method of the split-type zero-phase current transformer of the present disclosure includes a fixing step of storing and fixing in a mold a first workpiece in which a secondary coil is wound around a semi-annular multi-layered iron core, and a covering step of placing a spacer between the circumferential center of the inner surface of the first workpiece and the mold, and then pouring insulating resin into the mold and hardening it to obtain a second workpiece in which the iron core, secondary coil, and spacer are covered with insulating resin. [Effects of the Invention]

[0009] The manufacturing method of the split-type zero-phase current transformer disclosed herein has the effect of suppressing distortion of the multi-layered iron core due to the curing shrinkage stress of the insulating resin, thereby achieving stable characteristics without deteriorating the zero-phase current characteristics. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an external front view showing the configuration of a split-type zero-phase current transformer according to an embodiment. [Figure 2] FIG. 1 is a front view showing the configuration of a molded portion of a split-type zero-phase current transformer according to an embodiment. [Figure 3] FIG. 1 is a partial cross-sectional view showing the internal configuration of a molded portion of a split-type zero-phase current transformer according to an embodiment. [Figure 4] 1 is a process diagram illustrating a method for manufacturing a split-type zero-phase current transformer according to an embodiment of the present invention; [Figure 5] FIG. 1 is a front view showing the configuration of an iron core of a split-type zero-phase current transformer according to an embodiment. [Figure 6] FIG. 1 is a perspective view showing a lamination state of one layer region of an iron core of a split-type zero-phase current transformer according to an embodiment; [Figure 7] FIG. 1 is a front view showing a state in which the thermosetting tape according to the embodiment is wound around an iron core; [Figure 8] FIG. 1 is a cross-sectional view showing a state in which the thermosetting tape according to the embodiment is wound around an iron core. [Figure 9] FIG. 1 is a front view showing a state in which a secondary coil is wound around an iron core according to an embodiment. [Figure 10] FIG. 1 is a front view showing an insulating paper, an electromagnetic steel sheet shield, and a reinforcing plate arranged in a work in progress according to an embodiment; [Figure 11] FIG. 1 is a perspective view showing a configuration of an electromagnetic steel sheet shield disposed on an outer diameter portion of a work in progress according to an embodiment; [Figure 12] FIG. 10 is a perspective view showing the configuration of a reinforcing plate disposed on the inner diameter portion of the work in progress according to the embodiment; [Figure 13] FIG. 10 is a cross-sectional view showing a state in which a work in progress according to an embodiment is placed in a mold; [Figure 14] FIG. 1 is a perspective view showing a configuration of a spacer according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a split-type zero-phase current transformer and a split-type zero-phase current transformer according to an embodiment will be described in detail below with reference to the accompanying drawings.

[0012] Embodiment Fig. 1 is an external front view showing the configuration of a split-type zero-phase current transformer according to an embodiment. As shown in Fig. 1, the split-type zero-phase current transformer 1 according to the embodiment includes a molded portion 100, a fixed base 8 to which the molded portion 100 is fixed, and a fixing bolt 9 for fixing the molded portion 100 to the fixed base 8. The molded portion 100 includes secondary terminals 2 and 3 for outputting a secondary current, connection terminals 4 and 5 to which short-circuit wires 11 are connected that connect upper and lower secondary coils (described later) inside the molded portion 100, and test terminals 6 and 7 used when performing a characteristic test of the split-type zero-phase current transformer 1. By supplying a current to the test terminals 6 and 7, a secondary current corresponding to the current supplied to the test terminals 6 and 7 is output from the secondary terminals 2 and 3.

[0013] A U-phase primary conductor 31, a V-phase primary conductor 32, and a W-phase primary conductor 33, which constitute an electric circuit, are inserted into the hollow portion 10 of the molded portion 100 of the split-type zero-phase current transformer 1. The U-phase primary conductor 31 is a conductor through which a U-phase current of the three-phase AC current flows. The V-phase primary conductor 32 is a conductor through which a V-phase current of the three-phase AC current flows. The W-phase primary conductor 33 is a conductor through which a W-phase current of the three-phase AC current flows.

[0014] The secondary terminals 2 and 3 of the split-type zero-phase current transformer 1 output, as a zero-phase current, a secondary current corresponding to the sum of the vector of the current flowing in the U-phase primary conductor 31, the vector of the current flowing in the V-phase primary conductor 32, and the vector of the current flowing in the W-phase primary conductor 33. The split-type zero-phase current transformer 1 is provided, for example, in a ground fault directional relay or a ground leakage alarm. The ground fault directional relay or ground leakage alarm detects a leakage current based on the secondary current output as a zero-phase current from the secondary terminals 2 and 3 of the split-type zero-phase current transformer 1, and detects the occurrence of a ground fault in an electric circuit.

[0015] FIG. 2 is a front view showing the configuration of the molded portion 100 of the split-type zero-phase current transformer 1 according to the embodiment. FIG. 2 is a view in which the fixing base 8 and the fixing bolts 9 are removed from FIG. 1. FIG. 3 is a partial cross-sectional view showing the internal configuration of the molded portion 100 of the split-type zero-phase current transformer 1 according to the embodiment. FIG. 3 shows a cross-sectional view of only the upper part of the molded portion 100 as viewed from the front. As shown in FIG. 2, the molded portion 100 of the split-type zero-phase current transformer 1 is composed of an upper molded portion 101 on which test terminals 6 and 7 are provided, and a lower molded portion 102. The upper molded portion 101 and the lower molded portion 102 are fastened and fixed at their outer peripheries by a fastening band (not shown). As described above, the secondary coil in the upper molded portion 101 and the secondary coil in the lower molded portion 102 are connected between the connection terminals 4 and 5 by the short-circuit wire 11.

[0016] As shown in FIG. 3 , the upper molded section 101 of the molded section 100 of the split-type zero-phase current transformer 1 includes a semi-annular iron core 13, thermosetting tape 14, a secondary coil 15, insulating paper 16, an electromagnetic steel sheet shield 17 as a protector, a reinforcing plate 18, a resin spacer 19, and thermosetting resin 12 as an insulating resin that entirely covers these components. The semi-annular iron core 13 is composed of multiple layers. The thermosetting tape 14 covers the entire circumference of the iron core 13. The secondary coil 15 is wrapped around the entire circumference of the iron core 13 via the thermosetting tape 14. The insulating paper 16 is provided only on the outer diameter side of the secondary coil 15. The electromagnetic steel sheet shield 17 as a protector is provided only on the outer diameter side of the insulating paper 16. The reinforcing plate 18 is provided only on the inner diameter side of the secondary coil 15. The spacer 19 is provided on the inner diameter side of the reinforcing plate 18. Thermosetting resin 12 entirely covers iron core 13, thermosetting tape 14, secondary coil 15, insulating paper 16, electromagnetic steel sheet shield 17, reinforcing plate 18, and resin spacer 19, except for the vicinity of dividing surface 13a of iron core 13. Dividing surface 13a is the cut surface when annular iron core 13 is divided into two equal parts. Lower molded section 102 has a similar structure. Because the vicinity of dividing surface 13a of semi-annular iron core 13 is exposed from thermosetting resin 12, iron core 13 of upper molded section 101 and iron core 13 of lower molded section 102 can be closely attached at each dividing surface 13a.

[0017] The molded portion 100 of the split-type zero-phase current transformer 1 has test terminals 6 and 7. A test coil (not shown) is connected to the test terminals 6 and 7. The test coil is wound around the iron core 13 together with the secondary coil 15 and covered with thermosetting resin 12. The test coil is wound around the iron core 13 while protected by an insulating tube or the like to maintain insulation between the test coil and the secondary coil 15.

[0018] The thermosetting resin 12 is, for example, an epoxy resin, or may be a phenolic resin, a melamine resin, a urea resin, or a bismaleimide resin.

[0019] FIG. 4 is a process diagram illustrating a manufacturing method of the split-type zero-phase current transformer 1 according to the embodiment. Hereinafter, the manufacturing process of the split-type zero-phase current transformer 1 will be described with reference to FIG. 4. FIG. 5 is a front view illustrating the configuration of the core 13 of the split-type zero-phase current transformer 1 according to the embodiment. FIG. 5 illustrates an annular core 13 formed by combining two semi-annular cores 13. As shown in FIG. 5, the core 13 is configured with multiple layers. The core 13 is configured by combining multiple layers of cores formed with multiple core materials. In the embodiment, the core 13 is configured with three layer regions. The core 13 has a first core 20 in an inner layer, a second core 21 in an outer layer, and a third core 22 in a middle layer. For example, the first core 20 and the second core 21 are made of electromagnetic steel sheets, and the third core 22 is made of permalloy.

[0020] FIG. 6 is a perspective view showing the lamination state of one layer region of the core 13 of the split-type zero-phase current transformer 1 according to the embodiment. FIG. 6 shows the lamination state of, for example, the first core 20. The first core 20 is formed by laminating thin hoop material 35. For example, the first core 20 is fabricated by using a thin rectangular hoop material 35 as the core material. The starting portion of the hoop material 35 is fixed to a jig, and the hoop material 35 is wound around the jig so that it forms a circle, and then cutting the formed hoop material 35. The ending portion of the hoop material 35 wound around the jig is fixed, for example, by welding. The second core 21 and the third core 22 are also similarly formed by multiple layers of hoop material 35.

[0021] When manufacturing the split-type zero-phase current transformer 1, first, the entire periphery of the semi-annular iron core 13 made up of multiple layers is wrapped with the thermosetting tape 14 (FIG. 4: step S10). FIG. 7 is a front view showing the state in which the thermosetting tape 14 according to the embodiment is wrapped around the iron core 13. FIG. 8 is a cross-sectional view showing the state in which the thermosetting tape 14 according to the embodiment is wrapped around the iron core 13. FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. FIGS. 7 and 8 show the state in which the thermosetting tape 14 is wrapped around the annular iron core 13 formed by joining two semi-annular iron cores 13.

[0022] A work in progress 110 as a first work in progress shown in FIG. 7 is formed by winding a thermosetting tape 14 in a toroidal shape around an iron core 13 having a first iron core 20, a second iron core 21, and a third iron core 22. As shown in FIG. 2, the split-type zero-phase current transformer 1 is configured so that the split surface 13a of the iron core 13 is exposed, and therefore an exposed core region SP, for example, about 15°, where the thermosetting tape 14, secondary coil 15, etc. are not provided, is provided near the split surface 13a of the iron core 13. As shown in FIG. 2, secondary terminals 2 and 3 and connection terminals 4 and 5 are arranged in this exposed core region SP. This exposed core region SP is attached to a mold during casting and fixed in place with thermosetting resin 12.

[0023] The thermosetting tape 14 is wound, for example, in a half overlap manner, thereby improving the holding force of the iron core 13 with the thermosetting tape 14 and further suppressing the intrusion of the thermosetting resin 12 from the side surface of the iron core 13 when the thermosetting resin 12 is poured.

[0024] Because iron core 13 is layered, thermosetting resin 12 easily seeps into the gaps between the layers, and the stress generated when thermosetting resin 12 hardens causes distortion of the iron core and deteriorates its magnetic properties. Unlike single-layer iron cores, iron core 13 of the embodiment is composed of three layers, making gaps more likely to occur and significantly affecting the properties due to stress. Therefore, by wrapping thermosetting tape 14 around iron core 13, the layered structure is fixed and tightly adhered, and further, by preventing thermosetting resin 12 from seeping in from the side surfaces or divided surfaces 13a of iron core 13, the zero-phase current properties are improved.

[0025] Next, the secondary coil 15 is wound around the work-in-progress 110 in which the thermosetting tape 14 is wound around the semi-annular iron core 13 (FIG. 4: step S20). FIG. 9 is a front view showing the state in which the secondary coil 15 is wound around the iron core 13 according to the embodiment. FIG. 9 shows the state in which the secondary coil 15 is wound around the annular iron core 13 in which two semi-annular iron cores 13 are joined.

[0026] Work in progress 120, which serves as the first work in progress shown in Figure 9, is constructed by winding secondary coil 15 in a toroidal shape around work in progress 110 shown in Figure 7. Normally, secondary coil 15 is desirably wound at equal intervals around the entire circumference of the annular core, but in the case of a split type, it is necessary to provide connection parts such as secondary terminals 2 and 3 and connection terminals 4 and 5. Therefore, secondary coil 15 is wound at equal intervals around the portion excluding exposed core region SP near split surface 13a shown in Figure 7. Winding at equal intervals minimizes the effects of unbalance and enables accurate measurement of the phases of the three-phase current, resulting in stable residual current characteristics.

[0027] Furthermore, since the secondary coil 15 is wound on top of the thermosetting tape 14, it is possible to prevent the secondary coil 15 from shifting out of position and also to suppress distortion of the iron core 13 due to the winding stress of the secondary coil 15, thereby obtaining stable zero-phase current characteristics.

[0028] Next, insulating paper 16, electromagnetic steel sheet shield 17, and reinforcing plate 18 are arranged on work-in-progress 120 around which secondary coil 15 is wound ( FIG. 4 : step S30). FIG. 10 is a front view showing a state in which insulating paper 16, electromagnetic steel sheet shield 17, and reinforcing plate 18 according to the embodiment are arranged on work-in-progress 120. FIG. 10 shows a state in which insulating paper 16, electromagnetic steel sheet shield 17, and reinforcing plate 18 are arranged on annular iron core 13 formed by joining two semi-annular iron cores 13. In work-in-progress 130 as a first work-in-progress shown in FIG. 10, insulating paper 16 and electromagnetic steel sheet shield 17 are arranged on the outer diameter side of work-in-progress 120 shown in FIG. 9, and reinforcing plate 18 is arranged on the inner diameter side of work-in-progress 120. That is, insulating paper 16 and electromagnetic steel sheet shield 17 are arranged on the outer diameter side of secondary coil 15, and reinforcing plate 18 is arranged on the inner diameter side of secondary coil 15. Insulating paper 16 is arranged to protect the covering of secondary coil 15. As shown in Fig. 10, electromagnetic steel sheet shield 17 and reinforcing plate 18 have a semi-cylindrical shape with a central angle of approximately 150° that covers the area of ​​semi-annular iron core 13 except for exposed iron core area SP.

[0029] The iron core 13 shown in Figure 10 is composed of three layers: the first core 20, the second core 21, and the third core 22. The thickness of each core 20, 21, and 22 is one-third that of a single-layer core. Applying a simplified rectangular moment of inertia, the bending stress strength of each core 20, 21, and 22 is one-ninth that of a single-layer core. This creates a significant problem of degraded magnetic properties due to stress during the manufacturing process. Furthermore, the thermosetting resin 12, when cast and cured, experiences shrinkage stress, which stresses the iron core 13 and secondary coil 15. This causes distortion of the iron core 13 and misalignment of the secondary coil 15, resulting in poor residual current characteristics. Therefore, providing a protective magnetic steel shield 17 around the outer periphery improves mechanical strength. This also prevents magnetic fields and electromagnetic noise from external fields and suppresses leakage magnetic fields from the joints of the iron core 13.

[0030] 11 is a perspective view showing the configuration of an electromagnetic steel sheet shield 17 arranged on the outer diameter portion of a work-in-progress 130 according to the embodiment. For example, a rectangular hoop material made of a thin plate is used as the electromagnetic steel sheet shield 17. The electromagnetic steel sheet shield 17 is formed by stacking thin plates cut out into rectangular plates.

[0031] Similarly, measures are also required for the inner diameter portion of iron core 13 to prevent distortion of iron core 13 during the manufacturing process. Fig. 12 is a perspective view showing the configuration of reinforcing plate 18 arranged on the inner diameter portion of work-in-progress 130 according to the embodiment.

[0032] By disposing the reinforcing plate 18 on the inner diameter portion of the iron core 13, the mechanical strength of the iron core 13, which is made up of multiple layers, is supplemented, thereby suppressing distortion of the iron core 13 and achieving stable characteristics. Furthermore, the frequency of the primary conductor inserted into the hollow portion 10 of the split-type zero-phase current transformer 1 is generally 50 Hz or 60 Hz, and in order to suppress the effects of external electromagnetic waves from the primary conductor in the low-frequency range, a material with a high electromagnetic wave attenuation effect, such as copper, is used for the reinforcing plate 18.

[0033] In the work-in-progress 130 shown in FIG. 10, the work-in-progress 120, insulating paper 16, electromagnetic steel sheet shield 17 as a protective device, and reinforcing plate 18 are fixed together by wrapping cotton tape or the like (not shown) in a toroidal shape.

[0034] Next, the work-in-progress 130 is fixed to the mold 23, and a resin spacer 19 is placed in the mold 23 (FIG. 4: step S40). FIG. 13 is a cross-sectional view showing the work-in-progress 130 according to the embodiment placed in the mold 23. The mold 23 has an upper mold 23a and a lower mold 23b. The work-in-progress 130 shown in FIG. 13 is fixed to the mold 23 by fitting a portion of the semi-annular iron core 13 near the divided surface 13a at the end of the exposed iron core region SP into a groove 23c of the lower mold 23b. This prevents the work-in-progress 130 from shifting horizontally. Furthermore, the work-in-progress 130 and the upper mold 23a are fixed at two locations, positions P1 and P2, where the secondary terminals 2 and 3 and the connection terminals 4 and 5 are to be provided, preventing the work-in-progress 130 from shifting vertically.

[0035] Furthermore, a spacer 19 is placed between the circumferential center of the inner peripheral surface of work-in-progress 130 and lower mold 23b of mold 23. This prevents distortion of the central portion of semi-annular iron core 13, which is subjected to the most stress. By fixing work-in-progress 130 to mold 23 in this manner and pouring thermosetting resin 12 into the mold through a hole in the top of the mold and allowing it to harden, upper mold section 101 or lower mold section 102 is manufactured as a second work-in-progress (FIG. 4: step S50).

[0036] When iron core 13 is made up of a single layer, the use of reinforcing members such as electromagnetic steel sheet shield 17 and reinforcing plate 18 as protective equipment has made it possible to suppress distortion of iron core 13 due to stress during casting and hardening. However, when iron core 13 is made up of multiple layers, as in work-in-progress 130, the mechanical strength is greatly reduced, and distortion of the center of iron core 13 has been a major issue. Measures taken on the equipment side, such as in mold 23, have the problem of increased man-hours and costs.

[0037] In this embodiment, a triangular prism-shaped resin spacer 19 is disposed at the center of the inner circumferential surface of the work-in-progress 130 to physically suppress distortion of the iron core 13 due to the cure shrinkage stress of the thermosetting resin 12. FIG. 14 is a perspective view showing the configuration of the spacer 19 according to this embodiment. The longitudinal length of the triangular prism-shaped resin spacer 19 is the same as the width of the iron core 13. The width of the iron core 13 is the length of the iron core 13 along the central axis O of the iron core 13. The spacer 19 is disposed such that the longitudinal direction of a first surface 19a, which is one side surface of the triangular prism, is parallel to the central axis O of the iron core 13. The spacer 19 is disposed such that an extension line L1 of a line connecting a center q1 of a first side 19b corresponding to the first surface 19a of the triangle constituting the triangular prism of the spacer 19 and a vertex q2 opposite the first side 19b of the triangle coincides with the central axis O of the iron core 13.

[0038] The triangular prism-shaped spacer 19 is made of the same resin as the thermosetting resin 12, and its surface is polished to improve adhesion with the thermosetting resin 12. Using the same material for the spacer 19 as the thermosetting resin 12 reduces the amount of labor required for rework by the manufacturer, thereby reducing costs. An adhesive is applied to a first surface 19a of the spacer 19, which is one surface of the spacer 19, and the spacer 19 is bonded and fixed to the work-in-progress 130. If the spacer 19 is exposed on the surfaces of the upper mold section 101 and the lower mold section 102, the appearance quality will be reduced. Therefore, the spacer 19 is shaped like a triangular prism to minimize the contact area of ​​the spacer 19 with the mold 23 and minimize its exposure to the surfaces of the upper mold section 101 and the lower mold section 102, thereby improving the appearance quality. Furthermore, by providing a corner R (rounded corner) on one side q3 of the triangular prism that comes into contact with the mold 23, for example by adding a fillet of R2, it is possible to prevent wear on the mold 23 due to contact with the spacer 19, and to shape the spacer 19 so as to extend the use of the mold 23. Note that the spacer 19 may have a shape other than a triangular prism, such as a round prism or a polygonal prism, and may be made of a material different from the resin used as the thermosetting resin 12.

[0039] Once the upper mold section 101 and the lower mold section 102 have been manufactured as described above, the upper mold section 101 and the lower mold section 102 are joined at their respective dividing surfaces 13a to manufacture the mold section 100, and the fixing base 8 and the fixing bolts 9 are attached to the mold section 100, thereby manufacturing the split-type zero-phase current transformer 1 shown in Figure 1.

[0040] As described above, according to the embodiment, the spacer 19 is disposed between the center of the inner peripheral surface of the work-in-progress 130 and the mold 23, which suppresses distortion of the multi-layered iron core 13 due to cure shrinkage stress of the thermosetting resin 12, and stable characteristics can be obtained without deteriorating the zero-phase current characteristics. Furthermore, by forming the spacer 19 into a triangular prism shape, it is possible to manufacture the molded part 100 of the split-type zero-phase current transformer 1 that can obtain good characteristics without degrading the appearance quality.

[0041] The configurations shown in the above embodiments are examples of the contents of the present disclosure, and may be combined with other known technologies, and parts of the configurations may be omitted or modified within the scope of the gist of the present disclosure.

[0042] Various aspects of the present disclosure are summarized below as appendices.

[0043] (Appendix 1) a fixing step of storing and fixing in a mold the first work-in-progress in which the secondary coil is wound around a semi-annular multi-layered iron core; a covering step of disposing a spacer between the die and a central portion of the inner peripheral surface of the first work-in-progress in the circumferential direction, and then pouring insulating resin into the die and hardening the resin to obtain a second work-in-progress in which the iron core, the secondary coil, and the spacer are covered with the insulating resin; A method for manufacturing a split-type zero-phase current transformer, comprising: (Appendix 2) The spacer is made of the same material as the insulating resin. 2. A method for manufacturing a split-type zero-phase current transformer according to claim 1. (Appendix 3) The first work-in-progress has a semi-cylindrical reinforcing plate disposed on the inner diameter side of the secondary coil, In the fixing step, the first work-in-progress including the reinforcing plate is housed and fixed in the mold; In the covering step, the spacer is disposed between the reinforcing plate and the mold, and the second work-in-progress is obtained in which the iron core, the secondary coil, the reinforcing plate, and the spacer are covered with the insulating resin. 3. A method for manufacturing a split-type zero-phase current transformer according to claim 1 or 2. (Appendix 4) the spacer has a triangular prism shape, In the covering step, the spacer is arranged so that the longitudinal direction of a first surface, which is one side surface of the triangular prism, is parallel to the central axis of the iron core. 4. A method for manufacturing a split-type zero-phase current transformer according to any one of claims 1 to 3. (Appendix 5) In the covering step, the spacer is arranged so that an extension of a line connecting a center of a first side corresponding to the first face of a triangle constituting the triangular prism and a vertex opposite to the first side of the triangle coincides with a central axis of the iron core. 5. A method for manufacturing a split-type zero-phase current transformer according to claim 4. (Appendix 6) The core has a three-layer structure having, from the inner diameter side to the outer diameter side, a first core, a third core, and a second core, the first core and the second core being made of electromagnetic steel sheets, and the third core being made of permalloy. 6. A method for manufacturing a split-type zero-phase current transformer according to any one of appendices 1 to 5. (Appendix 7) The first work-in-progress has an electromagnetic steel sheet shield disposed on the outer diameter side of the secondary coil, In the covering step, the second work-in-progress is obtained in which the iron core, the secondary coil, the reinforcing plate, the electromagnetic steel sheet shield, and the spacer are covered with the insulating resin. 4. A method for manufacturing a split-type zero-phase current transformer according to claim 3. (Appendix 8) In the first work-in-progress, a thermosetting tape is wound around the iron core, and the secondary coil is wound around the thermosetting tape, In the covering step, the second work-in-progress is obtained in which the iron core, the thermosetting tape, the secondary coil, the reinforcing plate, the electromagnetic steel sheet shield, and the spacer are covered with the insulating resin. 8. A method for manufacturing a split-type zero-phase current transformer according to claim 7. (Appendix 9) The semi-annular iron core has a split surface which is a cut surface where the annular iron core is split into two, The second work-in-progress is a semi-annular core, the portion of which excluding the dividing surface is covered with the insulating resin. 9. A method for manufacturing a split-type zero-phase current transformer according to any one of appendices 1 to 8. (Appendix 10) a semi-annular multi-layer iron core; a secondary coil wound around the iron core; a spacer provided on the inner diameter side of the secondary coil and at the circumferential center of the inner circumferential surface of the iron core; an insulating resin that coats the iron core, the secondary coil, and the spacer; A split-type zero-phase current transformer comprising: (Appendix 11) The spacer is made of the same material as the insulating resin. 11. The split-type zero-phase current transformer according to claim 10. (Appendix 12) A semi-cylindrical reinforcing plate is disposed between the inner diameter side of the secondary coil and the spacer. 12. The split-type zero-phase current transformer according to claim 10 or 11. (Appendix 13) the spacer has a triangular prism shape, The spacer is arranged so that the longitudinal direction of a first surface, which is one side surface of the triangular prism, is parallel to the central axis of the iron core. 13. The split-type zero-phase current transformer according to any one of appendices 10 to 12. (Appendix 14) The spacer is arranged so that an extension of a line connecting a center of a first side corresponding to the first face of a triangle constituting the triangular prism and a vertex opposite to the first side of the triangle coincides with a central axis of the iron core. 14. The split-type zero-phase current transformer according to claim 13, (Appendix 15) The core has a three-layer structure having, from the inner diameter side to the outer diameter side, a first core, a third core, and a second core, the first core and the second core being made of electromagnetic steel sheets, and the third core being made of permalloy. 15. The split-type zero-phase current transformer according to any one of appendices 10 to 14, (Appendix 16) An electromagnetic steel sheet shield is disposed between the outer diameter side of the secondary coil and the insulating resin. 16. The split-type zero-phase current transformer according to any one of appendices 12 to 15, (Appendix 17) The iron core is wrapped with thermosetting tape, and the secondary coil is wrapped around the thermosetting tape. 17. The split-type zero-phase current transformer according to claim 16, (Appendix 18) The semi-annular iron core has a split surface which is a cut surface where the annular iron core is split into two, The semi-annular core is covered with the insulating resin except for the divided surfaces. 18. The split-type zero-phase current transformer according to any one of appendices 10 to 17, [Explanation of symbols]

[0044] 1 Split type zero-phase current transformer, 2, 3 Secondary terminal, 4, 5 Connection terminal, 6, 7 Test terminal, 8 Fixing base, 9 Fixing bolt, 10 Hollow portion, 11 Short circuit wire, 12 Thermosetting resin, 13 Iron core, 13a Split surface, 14 Thermosetting tape, 15 Secondary coil, 16 Insulating paper, 17 Electromagnetic steel sheet shield, 18 Reinforcing plate, 19 Spacer, 20 First iron core, 21 Second iron core, 22 Third iron core, 23 Mold, 23a Upper mold, 23b Lower mold, 23c Groove portion, 31 U phase primary conductor, 32 V phase primary conductor, 33 W phase primary conductor, 35 Hoop material, 100 Mold portion, 101 Upper mold portion, 102 Lower mold portion, 110, 120, 130 Work in progress, SP Iron core exposed area.

Claims

1. a fixing step of accommodating and fixing in a mold the first work-in-progress in which the secondary coil is wound around a semi-annular multi-layered iron core; a covering step of disposing a spacer between the die and a central portion of the inner peripheral surface of the first work-in-progress in the circumferential direction, and then pouring insulating resin into the die and hardening the resin to obtain a second work-in-progress in which the iron core, the secondary coil, and the spacer are covered with the insulating resin; A method for manufacturing a split-type zero-phase current transformer, comprising:

2. The spacer is made of the same material as the insulating resin.

2. The method for manufacturing a split-type zero-phase current transformer according to claim 1.

3. The first work-in-progress has a semi-cylindrical reinforcing plate disposed on an inner diameter side of the secondary coil, In the fixing step, the first work-in-progress including the reinforcing plate is housed and fixed in the mold; In the covering step, the spacer is disposed between the reinforcing plate and the mold, and the second work-in-progress is obtained in which the iron core, the secondary coil, the reinforcing plate, and the spacer are covered with the insulating resin.

2. The method for manufacturing a split-type zero-phase current transformer according to claim 1.

4. the spacer has a triangular prism shape, In the covering step, the spacer is arranged so that the longitudinal direction of a first surface, which is one side surface of the triangular prism, is parallel to the central axis of the iron core.

2. The method for manufacturing a split-type zero-phase current transformer according to claim 1.

5. In the covering step, the spacer is arranged so that an extension line of a line connecting a center of a first side corresponding to the first face of a triangle constituting the triangular prism and a vertex opposite to the first side of the triangle coincides with a central axis of the iron core.

5. The method for manufacturing a split-type zero-phase current transformer according to claim 4.

6. The core has a three-layer structure having, from the inner diameter side to the outer diameter side, a first core, a third core, and a second core, the first core and the second core being made of electromagnetic steel sheets, and the third core being made of permalloy.

2. The method for manufacturing a split-type zero-phase current transformer according to claim 1.

7. the first work-in-progress has an electromagnetic steel sheet shield disposed on the outer diameter side of the secondary coil, In the covering step, the second work-in-progress is obtained in which the iron core, the secondary coil, the reinforcing plate, the electromagnetic steel sheet shield, and the spacer are covered with the insulating resin.

4. The method for manufacturing a split-type zero-phase current transformer according to claim 3.

8. In the first work-in-progress, a thermosetting tape is wound around the iron core, and the secondary coil is wound around the thermosetting tape, In the covering step, the second work-in-progress is obtained in which the iron core, the thermosetting tape, the secondary coil, the reinforcing plate, the electromagnetic steel sheet shield, and the spacer are covered with the insulating resin.

8. The method for manufacturing a split-type zero-phase current transformer according to claim 7.

9. The semi-annular iron core has a split surface which is a cut surface where the annular iron core is split into two, The second work-in-progress is a semi-annular core, the portion of which excluding the dividing surface is covered with the insulating resin.

9. A method for manufacturing a split-type zero-phase current transformer according to claim 1.

10. a semi-annular multi-layer iron core; a secondary coil wound around the iron core; a spacer provided on the inner diameter side of the secondary coil and at the center in the circumferential direction of the inner circumferential surface of the iron core; an insulating resin that coats the iron core, the secondary coil, and the spacer; A split-type zero-phase current transformer comprising:

11. The spacer is made of the same material as the insulating resin.

11. The split-type zero-phase current transformer according to claim 10.

12. A semi-cylindrical reinforcing plate is disposed between the inner diameter side of the secondary coil and the spacer.

11. The split-type zero-phase current transformer according to claim 10.

13. the spacer has a triangular prism shape, The spacer is arranged so that the longitudinal direction of a first surface, which is one side surface of the triangular prism, is parallel to the central axis of the iron core.

11. The split-type zero-phase current transformer according to claim 10.

14. The spacer is arranged so that an extension of a line connecting a center of a first side corresponding to the first face of a triangle constituting the triangular prism and a vertex opposite to the first side of the triangle coincides with a central axis of the iron core.

14. The split-type zero-phase current transformer according to claim 13.

15. The core has a three-layer structure having, from the inner diameter side to the outer diameter side, a first core, a third core, and a second core, the first core and the second core being made of electromagnetic steel sheets, and the third core being made of permalloy.

11. The split-type zero-phase current transformer according to claim 10.

16. An electromagnetic steel sheet shield is disposed between the outer diameter side of the secondary coil and the insulating resin.

13. The split-type zero-phase current transformer according to claim 12.

17. A thermosetting tape is wound around the iron core, and the secondary coil is wound around the thermosetting tape.

17. The split-type zero-phase current transformer according to claim 16.

18. The semi-annular iron core has a split surface which is a cut surface where the annular iron core is split into two, The semi-annular core is covered with the insulating resin except for the divided surfaces.

18. A split-type zero-phase current transformer according to claim 10, wherein the split-type zero-phase current transformer is a split-type zero-phase current transformer.

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