JP2007281131A - Resin mold coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin-molded coil in which a partial discharge hardly occurs. <P>SOLUTION: A winding wire is formed by winding an insulating coated conductor. The wire is molded with resin into a unit coil (2), and an electrostatic shielding layer (3) of conductor is formed on the surface of the unit coil (2). Two or more of the unit coil (2) covered with the electrostatic shielding layer (3) are arranged at a prescribed interval in an axial direction and connected in series. The whole of assemblies is molded with resin into a cylindrical object. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a resin molded coil used for induction devices such as transformers and reactors.

  As a coil used for induction devices such as a transformer and a reactor, a resin-molded coil 50 having a structure in which the periphery of the coil is molded with an insulating resin as shown in a sectional view of FIG. 11 is widely used. This resin mold coil 50 is manufactured by first producing a unit coil 51 in which an insulation-coated copper wire or insulation-coated copper strip is wound in a donut shape, and then stacking them in the axial direction and fixing them in a mold. The whole is molded by thermosetting resin. The connection method of the plurality of unit coils 51 differs depending on the application, but is generally connected in series for high-voltage equipment. The resin mold coil 50 has an advantage that it can be manufactured in a compact manner in addition to exhibiting excellent properties of insulation and flame retardancy.

  The resin cast for molding enters the gap between the copper wires or the copper strips constituting the unit coil 51, and improves the insulation between these conductors. However, since the unit coil 51 is formed by densely winding a copper wire or a copper band, the resin hardly enters a narrow gap between conductors. For this reason, a gap in which the resin is not impregnated may remain in the unit coil 51, or a minute gap may remain between the conductor and the resin even if impregnated.

  When a high voltage is applied to the unit coil 51, a potential difference is generated between the unit coil 51 and the ground or between the unit coils to generate a high electric field. The strength of the generated electric field is inversely proportional to the dielectric constant if the electric flux density is the same. Since the dielectric constant of the void portion is lower than that of the resin, the electric field strength in the void is 4 to 5 times that of the resin portion. If the value exceeds the breakdown electric field strength of air, partial discharge occurs in the air gap, leading to failure.

  As a conventional technique for solving such a problem, for example, Patent Document 1 discloses a technique for reducing the viscosity of an injected resin to prevent voids from remaining in the resin. Patent Document 2 discloses a technique for improving crack resistance and partial discharge resistance by providing a surface conductive layer made of a conductive polymer on the surface of a resin mold layer. Further, in Patent Document 3, when the lightning impulse enters the transformer, the highest voltage is applied to the unit coil close to the power supply terminal, so that the thickness of the insulating portion covering the inner peripheral side of the unit coil close to the power supply terminal is disclosed. A technique is disclosed in which the thickness is made thicker than the portion covering the inner peripheral side of another unit coil.

However, as a resin mold coil used for a special high voltage class transformer, the above-mentioned measures are not sufficient, and further techniques for preventing the occurrence of partial discharge are required.
Japanese Patent Laid-Open No. 08-316055 JP 08-264347 A Japanese Patent Application Laid-Open No. 07-122439

  The present invention has been made to solve such problems of the prior art, and an object thereof is to provide a resin molded coil in which partial discharge is unlikely to occur.

  According to a first aspect of the present invention for solving the above-described problem, the surface of the unit coil (2) formed by resin molding a winding formed by winding an insulation-coated conductor and formed into a substantially annular shape is an electrostatic shield made of a conductor. The unit coil on which the layer (3) is formed and the electrostatic shield layer is formed is arranged in series with a plurality of unit coils arranged at predetermined intervals in the axial direction. This is a resin-molded coil that is molded into a cylinder by resin molding.

  When the electrostatic shield layer is provided around the unit coil as described above, the potential of the electrostatic shield layer is approximately an average value of the potential of each winding constituting the unit coil. Therefore, the potential difference between each winding and the electrostatic shield layer is reduced. Also, the potential difference between the windings in the electrostatic shield layer is reduced. For these reasons, even if a minute gap exists around the unit coil in the electrostatic shield layer, the partial discharge is less likely to occur.

  Further, by providing the electrostatic shield layer, the voltage applied to each unit coil when a surge voltage with a fast rise is applied to the resin molded coil is averaged. As a result, a voltage significantly higher than the others is not applied to the unit coil connected to a position near the input terminal of the resin mold coil. Therefore, there is an effect that partial discharge in the vicinity of these unit coils is also suppressed.

  The invention according to claim 2 is the resin molded coil according to claim 1, wherein a surface conductor layer (30) for surface grounding is formed on the surface of the resin molded coil. It is a resin mold coil.

  If such a surface conductor layer is formed and grounded, the safety of the apparatus can be improved. Although the distance from the electrostatic shield layer to the ground is shortened by the formation of the surface conductor layer, a minute gap is not formed in the mold layer outside the electrostatic shield layer, so there is little fear of partial discharge.

  Moreover, the invention according to claim 3 is the resin molded coil according to claim 1 or 2, wherein a capacitor (19) is connected between the adjacent electrostatic shield layers in the plurality of unit coils. These capacitors are also resin-molded coils that are integrally resin-molded with a plurality of unit coils.

  The resin molded coil having such a configuration has the same effect as the resin molded coil according to claim 1. Furthermore, the addition of a capacitor further weakens the electric field strength near the unit coil connected near the input terminal of the resin mold coil when a surge voltage is applied. Therefore, even if a minute gap exists in the vicinity of these unit coils, there is an effect that partial discharge is less likely to occur.

According to a fourth aspect of the present invention, in the resin-molded coil according to the first or second aspect, the adjacent electrostatic shield layers are brought close to each other around the connecting wire (20) between the adjacent unit coils. In this resin mold coil, the electrostatic capacitance between adjacent electrostatic shield layers is increased.
The resin molded coil having such a configuration has the same effects as the resin molded coil according to claim 3.

  The invention according to claim 5 is the resin molded coil according to claim 3, wherein the lead wire of the capacitor (19) connected between the adjacent electrostatic shield layers is connected to the electrostatic shield layer ( 25) is a resin-molded coil characterized in that adjacent capacitors are located at the same position.

  If lead wires of adjacent upper and lower capacitors are connected to the electrostatic shield layer 3 at a common connection point as in this configuration, surge current flowing across the capacitor will not flow through the electrostatic shield layer. Therefore, the potential distribution on the electrostatic shield layer is less likely to be disturbed by the surge current, and a strong electric field portion is less likely to be generated in the electrostatic shield layer. Thereby, generation | occurrence | production of partial discharge is suppressed.

  The invention according to claim 6 is the resin molded coil according to claim 3 or 5, wherein a plurality of the capacitors (19) are connected between the adjacent electrostatic shield layers. It is a molded coil.

  If a plurality of small-capacitance capacitors are arranged around the annular electrostatic shield layer, the potential distribution on the electrostatic shield layer can be further stabilized. Therefore, there is an effect that partial discharge is less likely to occur.

Hereinafter, the structural example of the resin mold coil which concerns on this invention is divided into embodiment, and is demonstrated.
(First embodiment)
FIG. 1 is a cross-sectional view showing the configuration of a resin molded coil 1 according to the first embodiment. The resin mold coil 1 is formed in a generally cylindrical or substantially rectangular tube shape as a whole, and is used through the center hole of the tube through a transformer iron core, a reactor iron core, or the like.

  FIG. 1 shows one side portion of a cross section including the central axis of the cylindrical resin molded coil 1. The resin mold coil 1 is formed by connecting a plurality of substantially circular coils 2 called unit coils. The unit coil 2 is formed by winding an insulating coated copper wire in a substantially annular shape and molding the whole with an insulating resin. An insulated copper band may be used instead of the insulation-coated copper wire.

  As a feature of the resin molded coil 1 of this embodiment, an electrostatic shield layer 3 is formed on the surface of each molded unit coil 2. The electrostatic shield layer 3 is formed by winding a conductive tape having a relatively high electrical resistance. Instead of the conductive tape, the electrostatic shield layer 3 may be formed by applying a conductive paint or spraying metal.

  A plurality of unit coils 2 having the electrostatic shield layer 3 formed on the surface thereof are arranged at predetermined intervals in the axial direction. And they are connected in series by a crossover wiring (20). Each electrostatic shield layer 3 is independent and is insulated from the others. The plurality of unit coils 2 are molded into a cylindrical shape by resin as a whole in such a state. Lead wires 5 and 6 are drawn out from unit coils located at both ends in the axial direction.

  As described above, in the resin molded coil 1 of this embodiment, the electrostatic shield layer 3 that is electrically insulated from the other is formed on the surface of each unit coil 2 as compared with the conventional resin molded coil 50 shown in FIG. It is characterized by being.

  Next, the effect of forming the electrostatic shield layer 3 on the surface of each unit coil 2 will be described. FIG. 2 is an electrical equivalent circuit of the resin molded coil 1 of the present embodiment. Each unit coil 2 is connected in series, and the unit coils 2 at both ends are connected to external input terminals 7 and 8 by lead wires 5 and 6. Each unit coil 2 is individually shielded by an insulated electrostatic shield layer 3.

  Assume that a high voltage V is applied to the input terminals 7 and 8 in this state. If the number of unit coils 2 is n, a high potential difference of V / n is generated between the windings located at both ends of each unit coil 2. A high potential difference is generated between the windings other than both ends and other windings in the same unit coil 2, although not as high as V / n.

  Further, a high potential difference is generated between each winding and the winding of the adjacent unit coil 2. Here, consider the case of the resin molded coil 50 of FIG. 11 in which the electrostatic shield layer 3 is not formed. The physical arrangement of the windings constituting the unit coil 2 is as shown in FIG. Because of this arrangement, two windings belonging to adjacent unit coils 2 and having a high potential difference are arranged close to each other. As an example, the windings 53 and 54 in FIG. 11 belong to another unit coil 2, and a potential difference larger than V / n is generated between them.

  In addition to the potential difference between the windings, a high potential difference is also generated between each winding and the ground. This is because the input line of the applied voltage V has a high potential difference with respect to the ground (neutral point).

  Thus, when a high voltage is applied to both ends of the resin mold coil 50, each winding is high between the other winding in the same unit coil 51, the winding of the other unit coil 51, and further to the ground. It will have a potential difference. A value obtained by dividing the potential difference by the distance between them is an electric field. When the magnitude of the electric field exceeds the dielectric breakdown electric field of the insulator between them, partial discharge occurs.

  In the resin-molded coil 50 having the conventional structure shown in FIG. 11, such a portion where the potential difference between the windings and between the winding and the ground is locally large is likely to occur. As described in “Background Art”, it is difficult for mold resin to enter between windings constituting the unit coil 51. Therefore, minute gaps are likely to remain. When a high electric field as described above is applied to the remaining microvoids, the gas remaining in the microvoids causes dielectric breakdown and partial discharge occurs. Even if the minute gap is a vacuum, a partial discharge is generated through the vacuum space.

  In order to prevent the occurrence of partial discharge in such a minute gap, the potential difference between the windings and between the winding and the ground may be reduced. The electrostatic shield layer 3 provided on the surface of each unit coil 2 of the present embodiment aims to reduce this potential difference and prevent the occurrence of partial discharge in a minute gap.

  When the electrostatic shield layer 3 is provided on the surface of the unit coil 2, a capacitor is formed with a mold resin interposed between the windings constituting the unit coil 2 and the electrostatic shield layer 3. If this state is shown by an electrical equivalent circuit, there are innumerable microcapacitance floating capacitors 10 as shown in FIG. The distance between the winding of the unit coil 2 and the electrostatic shield layer 3 is narrow. When the interval between the winding of the unit coil 2 and the electrostatic shield layer 3 is narrow and the floating capacitor 10 exists between them, the potential of the electrostatic shield layer 3 as a conductor is almost the average value of the potential of each winding.

  When the electrostatic shield layer 3 having such an average potential of each winding exists around the unit coil 2, the potential difference between each winding and the electrostatic shield layer 3 is the potential difference V between both ends of each unit coil 2. A small value of 1/2 or less of / n. Therefore, even if a minute gap exists in the unit coil 2 inside the electrostatic shield layer 3, it is difficult for discharge to occur between the winding and the electrostatic shield layer 3.

  Further, when the electrostatic shield layer 3 having the average potential of each winding is present in the periphery, the potential difference between windings belonging to the same unit coil 2 is not easily increased. The value is smaller than when the electrostatic shield layer 3 is not present. Accordingly, it is difficult for electric discharge to occur between windings belonging to the same unit coil 2.

  For the outer portion of the electrostatic shield layer 3, a high potential difference is generated between the electrostatic shield layer 3 and the ground. However, there are almost no microvoids in the resin layer outside the electrostatic shield layer 3. In addition, the electrostatic shield layer 3 has the same potential. For this reason, unlike the case where the electrostatic shield layer 3 is not formed, the electric field strength in the outer portion of the electrostatic shield layer 3 is almost the same in all portions, and the phenomenon that a high electric field is locally generated does not occur. Therefore, the partial discharge hardly occurs in the outer portion of the electrostatic shield layer 3.

  For this reason, in the resin molded coil 1 of the present embodiment, the provision of the electrostatic shield layer 3 does not cause a portion where a high electric field is locally generated. Therefore, even if a minute gap exists in the unit coil 2, there is an effect that partial discharge hardly occurs.

  Furthermore, another effect when the electrostatic shield layer 3 is provided will be described in relation to the effect in the second and subsequent embodiments described later. The effect is related to the non-uniformity of the voltage applied to each unit coil 2 when a surge voltage is applied to the resin mold coil 1.

  FIG. 4 shows a main current path when a surge voltage having a fast rise is applied when the electrostatic shield layer 3 is not provided (corresponding to the resin mold coil 50 having the conventional structure in FIG. 11). is there. The main stray capacitors are also shown in the figure. The floating capacitors include a floating capacitor 12 between adjacent unit coils 2 and a floating capacitor 13 between each unit coil 2 and the ground GND.

  For a surge voltage that rises quickly, the impedance of the unit coil 2 is large, and the impedances of the floating capacitors 12 and 13 are conversely small. For this reason, when a surge voltage having a fast rise is applied between the input terminals 7 and 8, the surge current does not flow through the unit coil 2, but generally flows through the current path 15 or 16 in the figure. The current path 15 is a path that flows across the floating capacitors 12 connected in series. The current path 16 temporarily flows to the ground GND through the floating capacitor 13 between the unit coil 2 and the ground GND, and then flows again to the opposite input terminal through the floating capacitor 13 between the unit coil 2 and the ground GND. It is.

  Here, the voltage applied to both ends of each unit coil 2 will be considered. For convenience, it is assumed that the capacity of each floating capacitor 12 is equal and the capacity of each floating capacitor 13 is also equal. When the capacitance of each floating capacitor 13 is zero, the voltage applied to each floating capacitor 12, that is, the voltage applied to both ends of each unit coil 2 is equal. That is, the surge voltage is applied equally by each unit coil 2.

  However, there is actually a floating capacitor 13 between the unit coil 2 and the ground GND. If the floating capacitor 13 is present, a part of the current flowing from the input terminal 7 in FIG. 7 flows to the ground GND through the floating capacitor 13 located near the input terminal 7. Then, after flowing through the ground GND, it flows out to the input terminal 8 through the floating capacitor 13 at a position close to the input terminal 8 on the opposite side. Therefore, a relatively large current flows through the floating capacitor 12 between the unit coils 2 connected to positions close to the input terminals 7 and 8. On the other hand, only a small current flows through the floating capacitor 12 between the unit coils 2 connected at a position close to the center.

  The voltage applied to each unit coil 2 is obtained by multiplying the impedance of the floating capacitor 12 in that portion by the value of the current flowing therethrough. Therefore, the voltage applied to the unit coil 2 connected to a position close to the input terminals 7 and 8 through which a large current flows increases, and the voltage applied to the unit coil 2 connected to a position close to the center decreases. That is, nonuniformity occurs in the voltage applied to the unit coil 2. The non-uniformity becomes stronger as the capacitance of the floating capacitor 13 between the ground coil and the ground GND increases, and decreases as the capacitance of the floating capacitor 12 between the unit coils 2 increases.

  When a surge voltage is applied in this way, a large voltage is applied to the unit coil 2 connected in the vicinity of the input terminals 7 and 8, and partial discharge is likely to occur in a minute gap in the vicinity thereof. In order to prevent this partial discharge, it is necessary to equalize the voltage applied to each unit coil 2 and prevent a nonuniform large voltage from being applied only to some of the unit coils 2. For this purpose, it is sufficient to devise so that the current flowing through the current path 15 in FIG. 4 is large and the current flowing through the current path 16 is not small. For this purpose, as described above, the capacitance of the floating capacitor 13 between the unit coil 2 and the ground GND is small, and the capacitance of the floating capacitor 12 between the unit coils 2 may be increased.

  Here, when returning to the structure of the resin molded coil 1 shown in FIG. 1 of the present embodiment, the equivalent circuit corresponding to FIG. 4 is as shown in FIG. The capacitor corresponding to the floating capacitor 12 between the unit coils 2 in FIG. 4 is the floating capacitor 17 between the winding of the unit coil 2 and the electrostatic shield layer 3 in the equivalent circuit of FIG. A floating capacitor 18 between 3 is connected in series. The interval between the unit coil 2 and the electrostatic shield layer 3 is formed narrow. Therefore, the capacitance of the floating capacitor 17 between the unit coil 2 and the electrostatic shield layer 3 is a very large value. Moreover, the adjacent electrostatic shield layers 3 are in a state where large area portions approach each other as shown in FIG. Therefore, the value of the floating capacitor 18 between the adjacent electrostatic shield layers 3 is also a very large value.

  On the other hand, in the floating capacitor 12 between the unit coils 2 in the equivalent circuit of FIG. 4 in which the electrostatic shield layer 3 is not provided, the distance between the windings corresponding to the electrode of the capacitor is long and the area of the facing portion is small. . Therefore, the capacity is a small value.

  For this reason, the series capacitance of the floating capacitors 17 and 18, which is the capacitance between the adjacent unit coils 2 in the equivalent circuit of FIG. 5, is larger than the capacitance of the floating capacitor 12 between the adjacent unit coils 2 in FIG. Become. Therefore, when a surge voltage is applied, the current flowing through the current path 15 of the equivalent circuit of FIG. 5 is larger than the current flowing through the current path 15 of the circuit of FIG. As a result, the voltage applied to each unit coil 2 is equalized as compared with the case of the circuit of FIG. 4 for the reasons described above, and no particularly large voltage is applied between the unit coils 2 near the input terminals 7 and 8.

  If the voltage applied between the unit coils 2 decreases, the voltage between the unit coils 2 and the electrostatic shield layer 3 also decreases. If the voltage is lowered, the electric field strength at the inner portion of the electrostatic shield layer 3 is also weakened. Therefore, even if a minute gap remains in the electrostatic shield layer 3, partial discharge is less likely to occur.

  Thus, in the resin mold coil 1 of this embodiment, the electric field strength in the unit coil 2 is weakened by providing the electrostatic shield layer 3. Therefore, even if a minute gap remains in the vicinity of the windings of these unit coils 2, there is an effect that partial discharge is less likely to occur.

(Second Embodiment)
In FIG. 6, the structure of the resin mold coil 1a which concerns on 2nd Embodiment is shown with sectional drawing. In the resin molded coil 1a of this embodiment, a capacitor 19 is added between adjacent electrostatic shield layers 3 of the resin molded coil 1 according to the first embodiment shown in FIG. The equivalent circuit is as shown in FIG. The added capacitor 19 is connected in parallel to the floating capacitor 18 between the adjacent electrostatic shield layers 3 and increases the capacitance between the adjacent electrostatic shield layers 3.

  When the electrostatic capacitance between the adjacent electrostatic shield layers 3 increases, as described in the first embodiment, when a surge voltage is applied between the input terminals 7 and 8 of the resin molded coil 1a, the current path 15 is changed. The flowing current increases. As a result, the voltage applied to each unit coil 2 tends to be equalized, and the voltage applied between the unit coils 2 connected near the input terminals 7 and 8 becomes low.

  As a result, the voltage between the unit coil 2 and the electrostatic shield layer 3 is also reduced, and the electric field strength at the inner portion of the electrostatic shield layer 3 is also reduced. Thereby, partial discharge is less likely to occur in the electrostatic shield layer 3.

  Thus, in the resin mold coil 1a of this embodiment, the addition of the capacitor 19 further weakens the electric field strength near the unit coil 2 near the input terminals 7 and 8 when a surge voltage is applied. Therefore, even if minute gaps remain in the vicinity of these unit coils 2, there is an effect that partial discharge is less likely to occur.

(Third embodiment)
In FIG. 8, the structure of the resin mold coil 1b which concerns on 3rd Embodiment is shown with sectional drawing. The resin molded coil 1b of the present embodiment is different from the resin molded coil 1a shown in FIG. 6 in the manner of forming the capacitor 19 provided between the adjacent electrostatic shield layers 3. In the present embodiment, adjacent electrostatic shield layers 3 around the crossover wiring 20 between the unit coils 2 are brought close to each other, thereby increasing the capacitance between adjacent electrostatic shield layers. The equivalent circuit in this case is the same as that shown in FIG.

  If such a capacitor 19a is formed between the adjacent electrostatic shield layers 3, the electric field strength in the vicinity of the unit coil 2 near the input terminals 7 and 8 when a surge voltage is applied as in the case of the second embodiment. Is further weakened. Therefore, even if minute gaps remain in the vicinity of these unit coils 2, there is an effect that partial discharge is less likely to occur.

(Fourth embodiment)
In FIG. 9, the structure of the resin mold coil 1c which concerns on 4th Embodiment is shown with sectional drawing. The resin mold coil 1c of this embodiment is a modified embodiment of the resin mold coil 1a according to the second embodiment shown in FIG. The difference from the configuration shown in FIG. 6 is the connection position of the capacitor 19 added between the adjacent electrostatic shield layers 3 to the electrostatic shield layer 3.

  In the configuration shown in FIG. 6, the lead wires of the upper and lower capacitors 19 connected to one electrostatic shield layer 3 are connected at different positions 25 a and 25 b on the electrostatic shield layer 3. On the other hand, in this embodiment, the lead wires of the upper and lower capacitors 19 are connected to the electrostatic shield layer 3 at a common connection point 25 as indicated by a connection point 25 in FIG. That is, they are connected at a common point.

  When the lead wires of the upper and lower capacitors 19 are connected to the electrostatic shield layer 3 at different positions, a surge current flowing through the current path 15 in FIG. 5 flows through the electrostatic shield layer 3 by applying a surge voltage. It will be.

  Each electrostatic shield layer 3 has an annular shape, and when the unit coil 2 is considered as a primary coil, each electrostatic shield layer 3 forms a secondary winding of one turn. Therefore, when a current is passed through the unit coil 2, a current also flows through the electrostatic shield layer 3 to generate heat. The current also serves to weaken the magnetic flux generated in the iron core passing through the center holes of the resin mold coils 1b and 1c. In order to reduce the current flowing through the electrostatic shield layer 3, the electrostatic shield layer 3 is formed of a conductor having a certain value of specific resistance.

  Therefore, in the case of the configuration as shown in FIG. 6, a surge current flows across the capacitor 19 on the electrostatic shield layer 3 between the connection points 25a and 25b, and a potential difference is generated therebetween. The potential difference disturbs the potential distribution on the electrostatic shield layer 3 and may cause a strong electric field portion in the electrostatic shield layer 3. Partial discharge is likely to occur in a strong electric field portion.

  On the other hand, in the configuration of this embodiment shown in FIG. 9, the lead wires of the upper and lower capacitors 19 are connected to the electrostatic shield layer 3 at a common connection point 25. Therefore, the surge current that flows across the capacitor 19 does not flow on the electrostatic shield layer 3. Therefore, the electric potential distribution on the electrostatic shield layer 3 is not disturbed thereby, so that a strong electric field portion is hardly generated in the electrostatic shield layer 3. As a result, an effect that partial discharge is less likely to occur is obtained.

  In the case of the configuration of FIG. 9 also, the floating capacitor 17 shown in FIG. 7 exists between the winding of the unit coil 2 and the electrostatic shield layer 3, so that the current flowing through the floating capacitor 17 is static. It flows through the electric shield layer 3 and reaches the connection point 25. A potential difference is generated on the electrostatic shield layer 3 in the flow process. In order to reduce the potential difference, the distance to the connection point 25 to which the capacitor 19 is connected may be shortened.

  For this reason, a plurality of small-capacitance capacitors can be arranged around the annular electrostatic shield layer 3 at equal intervals instead of connecting one large-capacitance capacitor 19 to the adjacent electrostatic shield layer 3. desirable. With such an arrangement, the potential distribution on the electrostatic shield layer 3 can be more stabilized than in the case shown in FIG. 9, and the occurrence of partial discharge can be more effectively suppressed.

(Other embodiments)
A surface conductor layer may be further formed on the outer surface of each resin molded coil in the first to fourth embodiments. FIG. 10 is a cross-sectional view when such a surface conductor layer 30 is formed on the surface of the resin molded coil 1 according to the first embodiment. Such a surface conductor layer 30 is formed by winding a conductive tape having a relatively high electrical resistance, applying a conductive paint, or spraying a metal. In use, the surface conductor layer 30 is grounded. Thereby, safety can be increased.

  When such a grounded surface conductor layer 30 is provided on the outer surface of the resin mold coil 1d, the distance from the electrostatic shield layer 3 around the unit coil 2 to the ground is shortened. However, since a minute gap is hardly formed in the mold layer outside the electrostatic shield layer 3, partial discharge hardly occurs in that portion.

It is sectional drawing of the resin mold coil 1 which concerns on 1st Embodiment. It is an equivalent circuit of the resin mold coil 1 which concerns on 1st Embodiment. This is a state of a floating capacitor in the unit coil 2 having the electrostatic shield layer 3. It is a figure explaining the main electric current path | route when a surge voltage is added to the resin mold coil which does not have the electrostatic shield layer. It is a figure explaining the main electric current path | route when a surge voltage is added to the resin mold coil 1 which concerns on 1st Embodiment. It is sectional drawing of the resin mold coil 1a which concerns on 2nd Embodiment. It is a figure explaining the equivalent circuit and electric current path | route of the resin mold coil 1a which concern on 2nd Embodiment. It is sectional drawing of the resin mold coil 1b which concerns on 3rd Embodiment. It is sectional drawing of the resin mold coil 1c which concerns on 4th Embodiment. It is sectional drawing of the resin mold coil 1d which provided the electrostatic shield layer 30 on the outer surface. FIG. 2 is a view corresponding to FIG.

Explanation of symbols

  In the drawings, 1, 1a, 1b, 1c, 1d are resin molded coils, 2 is a unit coil, 3 is an electrostatic shield layer, 19 is a capacitor, 25 is a common connection point, and 30 is a surface conductor layer.

Claims (6)

  The unit coil (2), which is formed in a substantially annular shape by resin-molding a winding formed by winding an insulating coating conductor, has an electrostatic shield layer (3) formed of a conductor on the surface, and the electrostatic shield layer is formed. A plurality of unit coils are arranged in series with a predetermined interval in the axial direction, and the plurality of unit coils are resin-molded and finished into a cylindrical shape. Mold coil.   The resin mold coil according to claim 1, wherein a surface conductor layer (30) for surface grounding is formed on a surface of the resin mold coil.   3. The resin molded coil according to claim 1, wherein a capacitor (19) is connected between the adjacent electrostatic shield layers of the plurality of unit coils, and the capacitors are also integrated with the plurality of unit coils. A resin-molded coil which is resin-molded.   3. The resin molded coil according to claim 1, wherein the electrostatic shield layers adjacent to each other around the connecting wire (20) between the adjacent unit coils are brought close to each other to face each other and static electricity between the adjacent electrostatic shield layers is static. A resin molded coil having an increased electric capacity.   The resin-molded coil according to claim 3, wherein the connection position (20) of the lead wire of the capacitor (19) connected between the adjacent electrostatic shield layers to the electrostatic shield layer is set to the same position for the adjacent capacitors. There is a resin-molded coil.   6. The resin molded coil according to claim 3, wherein a plurality of the capacitors (19) are connected between adjacent electrostatic shield layers.

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