JP2855862B2 - Resin mold current transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin mold current transformer in which a primary winding has a high potential, and
The present invention relates to an insulation structure of a resin mold current transformer having a mold layer between coils between secondary and secondary windings.

[0002]

2. Description of the Related Art FIG. 4 is a schematic sectional view showing a general structure of a resin mold current transformer. A current transformer main body 1 is made of a thermosetting casting resin (for example, an epoxy casting) containing an inorganic powder as a filler. The ends of the primary windings of the current transformer body 1 are integrally cast into a resin mold layer 7 made of a cured product of the resin), and the primary conductors 8A and 8B partially embedded in the resin mold layer 7 Are connected to a high voltage system of, for example, a 6.9 kv class.
Is electrically connected to a low-voltage terminal (not shown) in a resin, and a current is measured by a measuring instrument connected to the low-voltage terminal.

FIG. 5 is an enlarged sectional view of a current transformer main body in a conventional resin mold current transformer. A current transformer main body 1 has a secondary winding 3 on a surface of a ring-shaped core 2 having a rectangular cross section.
Are formed by winding a coil conductor (for example, polyester copper wire, conductor diameter 1.2 mm) coated with insulation in a predetermined number of times. Further, as an inter-coil insulating layer 5, a thermosetting casting resin containing mica is applied to a polyester tape and semi-cured prepreg tape is taped to a predetermined thickness. It is kept at a predetermined size. Further, a primary winding 4 is formed by winding a coil conductor (polyester copper wire, 2.0 mm) a predetermined number of times around the outside thereof.
The current transformer main body 1 configured as described above is set in a casting mold, and a thermosetting casting resin is cast and heat-cured in a vacuum atmosphere, so that the heat-softened prepreg tape and its gap are formed. A resin mold current transformer having the inter-coil insulation 5 cured together with the impregnated thermosetting casting resin is obtained.

[0004]

In the resin mold current transformer constructed as described above, the thermally softened prepreg tape increases the adhesiveness during vacuum casting of the thermosetting casting resin, and the gap between the tapes increases. In order to confine air gaps or air bubbles contained in the semi-cured resin and impede the penetration of the casting resin, the inter-coil insulation 5
Air bubbles (also called voids) remain inside. If voids remain in the inter-coil insulation 5, the voltage between the coils is concentrated on the voids having a small dielectric constant and a low dielectric breakdown voltage based on the principle of capacitance division, and spark discharges repeatedly occur in the voids. Insulation between coils due to partial discharge phenomenon 5
May be damaged, and eventually the situation may progress to an insulation breakdown accident between the windings. In order to avoid such a situation, it is necessary to increase the insulation distance between the coils. However, this not only increases the size of the resin mold current transformer, but also hinders the magnetic coupling between the windings. In addition, the disadvantage that the current conversion characteristics are deteriorated is newly generated.

An object of the present invention is to provide a resin mold current transformer which does not generate partial discharge during operation by eliminating voids in insulation between coils, and therefore has excellent long-term reliability.

[0006]

According to the present invention, a secondary winding distributed and wound around a ring-shaped iron core having a rectangular cross section and a predetermined winding outside the secondary winding are provided. A primary winding distributed and wound while maintaining an inter-coil insulation distance is integrally cast in a resin mold layer made of a cured product of a thermosetting casting resin, and the secondary winding is sandwiched therebetween. The inter-coil insulation distance is previously held at a predetermined size by a pair of flat ring-shaped inter-coil spacers interposed between the primary coil and the thermosetting which is integrally cast with the inter-coil spacer. The primary and secondary windings are insulated from each other by a coil-to-coil mold layer made of a cured product of a cast resin.

A flat ring-shaped inter-coil spacer is made of a resin mold spacer having the same composition as a cured product of a thermosetting casting resin integrally cast, and the width of the ring of the inter-coil spacer is set to the width of the secondary winding. By making the width larger in the radial direction, the thickness of the inter-coil mold layer is maintained at a predetermined inter-coil insulation distance.

Further, the inter-coil spacer is provided with coil grooves for regulating the pitch between turns of the primary winding at equal intervals on the inner peripheral side and the outer peripheral side.

[0009]

[Function] By arranging a pair of flat ring-shaped inter-coil spacers between the coils and maintaining the insulation distance between the coils at a predetermined size, obstacles such as prepreg materials that confine the voids are eliminated, and the coil is removed. A function of casting a thermosetting casting resin into a voidless space in the space between the coils held by the interspacer is obtained, and therefore, a void-free intercoil mold layer can be easily formed.

[0010] Further, since the inter-coil spacer is a resin mold spacer made of a thermosetting casting resin having the same composition as the casting resin, the adhesiveness of the casting resin to the cured product and the difference in thermal expansion are improved. Since a tightly integrated mold layer between coils can be formed, a resin mold current transformer with excellent long-term stability without defects such as cracks due to thermal stress during operation can be obtained. By extending the width of the spacer to the side of the secondary coil and maintaining a predetermined inter-coil insulation distance on the inner and outer circumferences of the secondary coil, the inter-coil insulation distance can be reduced by determining the dimensions of the inter-coil spacer. A function that can be adjusted to a desired size is obtained.

Further, if the pitch between turns is regulated by providing coil grooves on the inner and outer peripheral edges of the inter-coil spacer to engage with the coil conductor, the casting resin can be interposed between the coils through the gap between the held turns. It is possible to facilitate the formation of the inter-coil mold layer containing no voids by supplying the same, and to maintain a good magnetic coupling between the coils to obtain a resin mold current transformer having good current transformation characteristics.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a sectional view showing a main part of a current transformer in a resin molded current transformer according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a main part in FIG. The same parts are given the same reference numerals, and duplicate explanations are omitted. In the figure, the current transformer body 11 is
The secondary winding 3 is distributed and wound around the ring-shaped iron core 2 via a buffering iron insulation 9 which is formed by butt-winding a foamed silicone rubber (manufactured by Nishikawa Rubber Co., Ltd., 2 mm in thickness) once. Further, the primary winding 4 is distributed-wound via a pair of flat ring-shaped inter-coil spacers 17 sandwiching the secondary winding from the axial end face side of the ring. As shown in FIG. 2, the inter-coil spacer 17 has a thickness t equal to the inter-coil insulation distance d, and the width of the ring is larger than the radial width w of the secondary winding by two.
d, and the coil-to-coil spacer is projected through the coil-to-coil spacer by projecting to the inside and outside of the secondary winding toward the coil-to-coil insulation distance d, respectively.
The secondary winding 4 holds a space corresponding to the inter-coil insulation distance d between the secondary winding 3 and the secondary winding 3. Therefore, when the current transformer main body 11 configured as described above is set in a casting mold and the inside of the mold is evacuated, and the thermosetting casting resin is vacuum-cast, voids are formed between the coils. Since there is no obstacle such as prepreg tape that traps the gap, the casting resin can be easily injected between the coils through the gap between the turns of the primary winding that has been wound in a distributed manner. Current transformer body 11 having inter-coil mold layer 15 not containing
Are molded integrally in the resin mold layer 7 to obtain a resin mold current transformer.

Table 1 is a characteristic table showing partial discharge characteristics of a 6 kv class resin molded current transformer according to an embodiment of the present invention in comparison with that of a conventional resin molded current transformer.
, A partial discharge starts at 1.1 kv, which is much lower than the ground operating voltage of 4.2 kv, and a large partial discharge of several thousands pc (pico coulomb) is continuously generated at the operating voltage. In the current transformer, the partial discharge starting voltage is at least twice the operating voltage, and the operating voltage is 4.
At 2kv, no partial discharge is generated, indicating that extremely excellent partial discharge characteristics can be obtained compared to conventional resin mold current transformers, eliminating the possibility of insulation damage due to partial discharge and ensuring long-term reliability. And a resin mold current transformer having a high value.

[0014]

[Table 1]

As shown in FIG. 2, if the inter-coil spacer 17 is manufactured in advance using a thermosetting casting resin having the same composition as that of the inter-coil mold layer 15, the inter-coil mold layer can be formed in the heat curing step. Since the adhesive strength between the coil 15 and the inter-coil spacer 17 can be maintained at a high level and the difference in thermal expansion between the two can be eliminated, the heat acting on the inter-coil mold layer 15 due to a change in the winding temperature during operation of the current transformer. It is possible to obtain a resin-molded current transformer in which the stress is kept to a minimum and defects such as cracks are unlikely to occur, and therefore, the long-term thermal stability is excellent. In addition, the insulation distance between the coils can be shortened with the improvement of the insulation performance, and the size of the resin mold current transformer can be reduced.

FIG. 3 is an enlarged view of an inter-coil spacer showing another embodiment of the present invention. A flat ring-shaped inter-coil spacer 27 has a coil groove 24 in which the coil conductor 4A is engaged with the inner peripheral side and the outer peripheral side. The primary windings are provided at equal pitches (equal angle Θ in the figure), and are wound by engaging the coil conductors 4A of the primary windings in the coil grooves 24 so that each turn pitch is uniformly distributed and wound. Since the wire is obtained, the casting resin can be easily supplied between the coils from the gap of the coil conductor to form a mold layer between the coils that does not include voids. By maintaining good electrical coupling, a resin mold current transformer having good current transformation characteristics can be obtained.

[0017]

As described above, according to the present invention, a pair of inter-coil spacers in the form of a flat ring are arranged between the coils so that the insulation distance between the coils is maintained in a predetermined size in advance. As a result, obstacles such as a prepreg material that traps voids in the inter-coil insulation, which has been a problem in the prior art, are eliminated, and a thermosetting casting resin is easily introduced into the space held between the coils to reduce voids. Can be formed, for example, the starting voltage of partial discharge is improved to twice or more of the operating voltage, so that partial discharge does not occur during operation, and insulation damage due to discharge deterioration It is possible to provide a resin-molded current transformer having an inter-coil mold layer having excellent long-term insulation reliability that does not cause long-term insulation reliability. This makes it possible to provide a downsized resin mold current transformer.

Further, if the inter-coil spacer is constituted by a resin mold spacer made of a thermosetting casting resin having the same composition as the casting resin, the adhesiveness to the cured product of the casting resin and the difference in thermal expansion are improved. It is possible to form an inter-coil mold layer in which the inter-coil spacer and the cured product of the casting resin are firmly integrated, so that a resin having excellent long-term stability without causing defects such as cracks due to thermal stress during operation. A molded current transformer is obtained, the insulation distance between the coils can be further shortened, and the width of the flat ring-shaped spacer between the coils is extended to the side of the secondary coil, so that the inner circumference and the outer circumference of the secondary coil are increased. If the side is configured to hold a predetermined inter-coil insulation distance, there is an advantage that the inter-coil insulation distance can be adjusted to a desired size by determining the dimensions of the inter-coil spacer.

Furthermore, if the pitch between turns is regulated by providing coil grooves on the inner peripheral edge and the outer peripheral edge of the inter-coil spacer to engage with the coil conductor, the casting resin is interposed between the coils through the gap between the held turns. It is possible to easily form the inter-coil mold layer that does not include voids by supplying the same, and it is possible to obtain a resin mold current transformer having good current transformation characteristics by maintaining good magnetic coupling between the coils.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a current transformer main part of a resin mold current transformer according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of FIG. 1;

FIG. 3 is an enlarged view of an inter-coil spacer portion showing another embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view showing a general structure of a resin mold current transformer.

FIG. 5 is a sectional view showing a current transformer main part of a conventional resin mold current transformer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current transformer main body 2 Ring-shaped iron core 3 Secondary winding 4 Primary winding 5 Insulation between coils 7 Resin mold layer 9 Iron core insulation 11 Current transformer main body 15 Coil mold layer 17 Coil spacer 24 Coil groove 27 Between coils Spacer

Continuation of the front page (56) References JP-A-59-22307 (JP, A) JP-A-55-129435 (JP, U) JP-A-56-32426 (JP, U) JP-A-56-32428 (JP, U) , U) (58) Fields investigated (Int.Cl. ⁶ , DB name) H01F 38/28 H01F 27/32 H01F 41/12

Claims (3)

(57) [Claims] A secondary winding distributed around a ring-shaped iron core having a rectangular cross section, and a primary winding distributed and wound outside the secondary winding while maintaining a predetermined insulation distance between coils, In a resin molded layer integrally formed in a resin mold layer made of a cured product of a thermosetting cast resin, the resin is formed so as to sandwich the secondary winding.
The inter-coil insulation distance is previously held at a predetermined size by a pair of flat ring-shaped inter-coil spacers interposed between the coil and the next coil, and the inter-coil spacer and the thermosetting injection molded integrally. A resin molded current transformer, wherein the primary winding and the secondary winding are insulated from each other by an inter-coil mold layer made of a cured product of a mold resin. 2. A flat ring-shaped inter-coil spacer comprising a resin mold spacer having the same composition as a cured product of a thermosetting casting resin integrally cast, wherein the width of the ring of the inter-coil spacer is set to be equal to that of the secondary winding. The resin molded current transformer according to claim 1, wherein the thickness of the inter-coil mold layer is maintained at a predetermined inter-coil insulation distance by making the width greater than the radial width. 3. The inter-coil spacer is provided with coil grooves for regulating the pitch between turns of the primary winding at equal intervals on the inner peripheral side and the outer peripheral side thereof.
The resin mold current transformer according to the above.