JP2021064772A - Current transformer and zero-phase current transformer - Google Patents

Abstract

To provide a current transformer and a zero-phase current transformer that do not cause product deformation due to thermal expansion in a high-temperature atmosphere of air pool that occurs in a gap between an outer case and a coil due to pressure molding of a heat-fluidized molding resin.SOLUTION: In a current transformer and zero-phase current transformer, a cylindrical vent 8a with a slit 19a open to the side of a filling region in at least one wall of a double cylindrical wall (inner cylinder 2 or outer cylinder 3) in a molding resin filling region separated from a molding resin filling gate position 20 of an outer case 1 by a predetermined value or more.SELECTED DRAWING: Figure 4

Description

The present invention relates to a current transformer and a zero-phase current transformer for measuring an alternating current or an alternating current in which a direct current is superimposed, for example, a half-wave sinusoidal alternating current or a leakage current thereof.

FIG. 6 is a schematic view showing a conventional general current transformer. In the conventional current transformer, the secondary winding W2 is wound around a closed magnetic path made of an annular magnetic core, and the primary winding W1 through which the current to be measured flows penetrates the central opening of the closed magnetic path. In that operation, when the current I1 flows through the primary winding W1, a preferably proportional current I2 corresponding to the magnitude of the current I1 is generated in the secondary winding W2 by electromagnetic induction. At this time, by connecting a bearing resistor to the secondary winding W2, a voltage signal is output to the secondary winding W2, and as a result, the current I1 flowing through the primary winding W1 can be measured as a voltage signal. Become.

As a conventional method for manufacturing a current transformer, a metal mold is prepared, a magnetic core having at least one winding, that is, a coil is inserted into the mold in a state of being incorporated in an outer case, and the mold is closed. There is a method of pressure molding and integrally sealing molding by filling a mold with a heat-fluidized molding resin under pressure. (See, for example, Patent Document 1)

Japanese Patent Application Laid-Open No. 7-183145 Fig. 3

FIG. 7 is an explanatory diagram of a conventional pressure molding method for a current transformer. As shown in the isometric view (a) and the top view (b) of FIG. 7, the outer case 1 in which the coil 12 and the lead wire 11 are incorporated is set in the mold (lower mold) 18 and is set in the mold (upper mold). The mold) 17 is closed, and the heat-fluidized molding resin is poured from the gate 9 of the mold (upper mold) 17 and pressure-molded to seal the coil 12. As the distance from the gate 9 decreases, the fluidity decreases as the temperature of the molding resin decreases, and the filling property decreases. Therefore, the inside of the outer case 1 is widely centered on the opposite side of the gate 9 when viewed from the central axis of the outer case 1. The molding resin is not filled to the bottom surface of the outer case 1 in the gap between the cylinder 2 and the outer cylinder 3 and the side surface of the coil 12, and an air pool is generated. When the current transformer is exposed to a high temperature atmosphere after pressure molding, the outer case 1 and the molding resin are deformed due to the expansion of the sealed internal air pool, and the specified outer shape cannot be maintained. Further, as the internal pressure increases, pressure is also applied to the coil 12, resulting in a decrease in electrical characteristics.

Further, as a measure against air accumulation, a method of evacuating the inside of the mold before filling with the molding resin can be considered, but it cannot be easily adopted because equipment such as a vacuum pump and a vacuum tank is required and the cost increases significantly.

Further, as shown in FIG. 8, a method of providing a simple ventilation hole as a measure for preventing the expansion of the air pool in a high temperature atmosphere can be considered, but the bottom view 8 (a) and the side view 8 (b) of the outer case 1 are considered. When the ventilation holes 21a and 21b as shown in the above are provided, the windings 13 constituting the coil 12 are exposed, so that the withstand voltage characteristics of the current transformer are significantly lowered and cannot be adopted.

In the current transformer or zero-phase current transformer in the present invention, a coil in which an annular magnetic core having a high relative permeability characteristic is wound is housed in a case having a bottom surface and a double cylindrical wall, and is heated and fluidized. The structure is such that the molding resin is poured into the case from the molding mold injection port and pressure-molded integrally with the coil, and the case is at least one of the double cylindrical walls in the molding resin filling region separated from the injection port by a predetermined value or more. The wall is provided with a groove having a notch shape on the side surface of the filling region of the wall, or a cylindrical ventilation hole having an open slit on the filling region side of the wall.

As described above, in the present invention, the air pool generated inside the current transformer is formed by a notch-shaped groove, a cylindrical vent hole, and a slit from the top surface to the bottom surface open to the filling region side of the cylindrical vent hole. By communicating with the outside air, it has the effect of preventing deformation of the molding resin and the case due to expansion of the internal air reservoir in a high temperature atmosphere.

It is a figure which shows the current transformer or the zero-phase current transformer in Embodiments 1 to 4 of this invention. It is a figure which shows the outer case structure used for the current transformer or the zero-phase current transformer in Embodiment 1 of this invention. It is a figure which shows the outer case structure used for the current transformer or the zero-phase current transformer in Embodiment 2 of this invention. It is a figure which shows the outer case structure used for the current transformer or the zero-phase current transformer in Embodiment 3 of this invention. It is a figure which shows the outer case structure used for the current transformer or the zero-phase current transformer in Embodiment 4 of this invention. It is a schematic diagram which shows a general current transformer. It is explanatory drawing of the pressure molding method of a general current transformer. It is a figure which shows the example of the outer case structure which has a low withstand voltage characteristic.

Embodiment 1.
FIG. 1 shows a current transformer or a zero-phase current transformer 100 according to the first embodiment of the present invention, FIG. 1A is a plan view, FIG. 1B is a sectional view taken along line AA, and FIG. 1C is a cross-sectional view taken along the line AA. 1 (d) is a front view, FIG. 1 (d) is an isometric view of the coil 12, and FIG. 1 (e) is an enlarged view of the air pool 16 in FIG. 1 (b).
12 shown in FIG. 1 (d) shows a toroidal-shaped magnetic core 15 for magnetic collection (shown in FIG. 1 (b)) and a toroidal-shaped case 14 for accommodating the magnetic core 15 (shown in FIG. 1 (b)). ) And the winding 13 (shown in FIG. 1B) for converting the change in magnetic flux in the magnetic core 15 wound around the case 14 containing the magnetic core 15 into an electric current, and 11 is a coil. A lead wire for a lead wire having a coating electrically connected to 12.
In FIG. 1A, 1 is an outer case for accommodating a part of the coil 12 and the lead wire 11, and 10 is a molding resin that is pressure-filled from the gate 9 (shown in FIG. 7) to seal the coil 12. .. Reference numeral 20 indicates the position of the gate 9.
FIG. 1 (e) shows a filling state in the molding resin filling region farthest from the gate position 20, the molding resin 10 is filled only to the depth of the dimension T, and the air pool 16 exists in a wide range. To do.
FIG. 2 is an outer case 1 used for the current transformer or the zero-phase current transformer 100 according to the first embodiment of the present invention, FIG. 2A is a plan view of the outer case 1, and FIG. 2B is AA. FIG. 2 (c) is an isometric view, and FIG. 2 (d) is an enlarged view of the notched grooves 7a and 7b shown in FIG. 2 (a).
In FIG. 2A, 4 is a lead wire insertion portion for accommodating a part of the lead wire 11 electrically connected to the winding 13 when the coil 12 is housed in the outer case 1, and 5 is a lead wire insertion portion 4. The lead wire lead-out portion, which is a through hole for pulling out the lead wire 11 to the outside of the outer case through the lead wire 11 housed in the lead wire insertion portion 4, is housed in the tip of the lead wire 11 housed in the lead wire insertion portion 4 and the outer case 1. This is a winding lead-out portion provided for passing an extra length wire of the winding 13 for electrically connecting the winding 13.
In FIGS. 2A and 2C, the outer case 1 has notched grooves 7a and 7b along the wall surface of the outer cylinder 3 on the molding resin filling region side, which are relative to the central axis of the outer case 1. A range in which the air reservoir 16 spreads around the opposite side of the gate 9 position 20 used for filling the molding resin (in the molding resin filling region, for example, an angle of 135 degrees or more on both sides of the gate position 20 centering on the central axis of the outer case 1). It is provided within a remote range). Here, two notched grooves are provided, but any number may be provided. The notch-shaped grooves 7a and 7b have a tip portion in the cross section and the angle to the tip portion is an acute angle (for example, 60 degrees), so that the notch-shaped grooves 7a and 7b tip portions are filled with the molding resin. Further, as shown in FIG. 2D, the tip portions of the notched grooves 7a and 7b are indicated by arrows in the resin flow direction (here, in FIG. 2D). The molding resin 10 injected from the gate position 20 flows in two directions, a clockwise direction and a counterclockwise direction, and indicates a state of collision at the point indicated by the double-headed arrow). The structure is made to have a lower filling property, and the tip portion is made a gap. Here, the notch-shaped groove 7a provided at a position where the flow direction of the resin is in the clockwise direction has a triangular shape having a tip angle of 60 degrees, for example, but this triangular shape is not an isosceles triangular shape. The shape is inclined by, for example, 60 degrees in the counterclockwise direction, which is the direction facing the flow direction of the resin. Further, the notch-shaped groove 7b provided at a position where the resin flow direction is counterclockwise has, for example, a triangular shape with a tip angle of 60 degrees, but this triangular shape is not an isosceles triangular shape. The shape is inclined by, for example, 60 degrees in the clockwise direction, which is the direction facing the flow direction of the resin. Further, although the cross section of the notched grooves 7a and 7b has a triangular shape with one tip, the number of tips may be arbitrary, for example, an anti-trapezoidal shape with two tips may be used.
In the current transformer or zero-phase current transformer 100 using the outer case 1 configured as described above, the outer case 1 is passed through the voids generated during filling with the molding resin at the tips of the notched grooves 7a and 7b. The air pool 16 generated between the outer cylinder 3 and the coil 12 is in a shape that communicates with the outside air, and the air inside the air pool 16 is discharged to the outside through the gaps at the tips of the notched grooves 7a and 7b even in a high temperature atmosphere. Since the pressure is reduced, the deformation of the outer case 1 and the molding resin 10 due to the thermal expansion of the air in the air reservoir 16 can be prevented.
Further, as shown in FIG. 1 (e), the creepage distance from the outside of the current transformer 100 to the winding 13 can secure the thickness T of the molding resin 10 (for example, 2.0 mm or more), so that the outer case 1 of FIG. 8 can be secured. Compared with the case where the outer case 1 is provided with the ventilation holes 21a or 21b so that the winding 13 of the coil 12 shown in the bottom view (a) and the side view (b) is exposed, the notched grooves 7a and 7b are provided. When provided, high withstand voltage characteristics can be obtained.

Embodiment 2.
In the present embodiment, a part different from the first embodiment will be described. FIG. 3 shows the outer case 1 of the current transformer or the zero-phase current transformer 100 according to the second embodiment of the present invention, FIG. 3 (a) is a plan view of the outer case 1, and FIG. 3 (b) is a line AA. A cross-sectional view, FIG. 3 (c) is an isometric view, and FIG. 3 (d) is an enlarged view of the notched grooves 7c and 7d shown in FIG. 3 (a).
In FIGS. 3A and 3C, the outer case 1 has notched grooves 7c and 7d along the wall surface of the inner cylinder 2 on the molding resin filling region side, which are relative to the central axis of the outer case 1. It is provided within a range in which the air reservoir 16 spreads around the opposite side of the position 20 of the gate 9 used for filling the molding resin. Here, two notched grooves are provided, but any number may be provided. The notch-shaped grooves 7c and 7d have a tip portion in the cross section and the angle to the tip portion is an acute angle (for example, 60 degrees), so that the notch-shaped grooves 7c and 7d tip portions are filled with the molding resin. Further, as shown in FIG. 3D, the tip portions of the notched grooves 7c and 7d are oriented with respect to the flow direction of the resin (indicated by arrows in FIG. 3D). By tilting them in opposite directions, the structure has a lower filling property, and the tip portion becomes a gap.
In the current transformer or zero-phase current transformer 100 using the outer case 1 configured as described above, when the molding resin is filled, the outer case is passed through the gaps generated at the tips of the notched grooves 7c and 7d. The air pool 16 generated between the inner cylinder 2 of 1 and the coil 12 communicates with the outside air, and even in a high temperature atmosphere, the air inside the air pool 16 passes through the notched groove 7c and the gap at the tip of the 7d to the outside. Since the pressure is reduced by being released, it is possible to prevent the outer case 1 and the molding resin 10 from being deformed due to the thermal expansion of the air in the air reservoir 16.
Further, as shown in FIG. 1 (e), the creepage distance from the outside of the current transformer 100 to the winding 13 can be secured, so that the thickness T of the molding resin 10 can be secured. Compared with the case where the vent holes 21a or 21b so as to expose the winding 13 of the coil 12 shown in FIG. (B) are provided in the outer case 1, the withstand voltage is higher when the notched grooves 7c and 7d are provided. The characteristics can be obtained.

Embodiment 3.
In the present embodiment, a part different from the first embodiment will be described. FIG. 4 is an outer case 1 of the current transformer or zero-phase current transformer 100 according to the third embodiment of the present invention, FIG. 4 (a) is a plan view, and FIG. 4 (b) is a sectional view taken along line AA. 4 (c) is an isometric view, and FIG. 4 (d) is a sectional view taken along line BB.
In FIGS. 4A, 4C, and 4D, the outer case 1 has a vent hole 8a of an arbitrary shape having a size that does not hinder the molding of the outer case 1 on the outer cylinder 3 as the outer case central axis. On the other hand, it has an arbitrary number (for example, one) within a range in which the air reservoir 16 spreads around the opposite side of the gate position 20 used for filling the molding resin. The vent hole 8a has a slit 19a that leads from the top surface to the inside of the outer case 1 (molding resin filling region side), and the slit 19a is formed by the vent hole 8a and the upper part of the slit 19a when the molding resin is filled. Those having a width (for example, 0.5 mm) and a depth (for example, T + 2.0 mm or more in FIG. 1 (e)) so as not to be blocked by the molding resin 10 up to the position of the bottom of the slit 19a while being blocked by the molding resin 10. And.
In the current transformer or zero-phase current transformer 100 configured in this way, the air pool 16 communicates with the outside air through the ventilation holes 8a and the slits 19a, so that the air in the air pool 16 can flow even in a high temperature atmosphere. Since the pressure is reduced by being discharged to the outside through the ventilation holes 8a, it is possible to prevent the outer case 1 and the molding resin 10 from being deformed due to the thermal expansion of the air in the air reservoir 16.
Further, as shown in FIG. 4D, by securing the length L from the bottom of the slit 19a to the bottom of the outer case (for example, 2 mm or more), the creepage distance from the surface of the current transformer 100 to the winding 13 is secured. Therefore, as compared with the case where the outer case 1 is provided with the ventilation holes 21a or 21b so that the winding 13 of the coil 12 shown in the bottom view (a) and the side view (b) of the outer case 1 of FIG. 8 is exposed. High withstand voltage characteristics can be obtained.

Embodiment 4.
In the present embodiment, a part different from the first embodiment will be described. 5A and 5B are an outer case 1 of a current transformer or a zero-phase current transformer 100 according to a fourth embodiment of the present invention, FIG. 5A is a plan view, and FIG. 5B is a sectional view taken along line AA. 5 (c) is an isometric view, and FIG. 5 (d) is a sectional view taken along line BB.
In FIGS. 5A, 5C, and 5D, the outer case 1 has an arbitrary shape vent hole 8b having a size that does not hinder the formation of the mold of the outer case 1 on the inner cylinder 2 as the outer case central axis. On the other hand, it has an arbitrary number (for example, one) within a range in which the air reservoir 16 spreads around the opposite side of the gate position 20 used for filling the molding resin. The vent hole 8b has a slit 19b that leads from the top surface to the inside of the outer case 1 (molding resin filling region side), and the slit 19b is formed by the vent hole 8b and the upper part of the slit 19b when the molding resin is filled. It has a width (for example, 0.5 mm) and a depth (for example, T + 2.0 mm or more in FIG. 1 (e)) so that the position of the bottom of the slit 19b is not blocked by the molding resin 10 while being blocked by the molding resin 10. To do.
In the current transformer or zero-phase current transformer 100 configured in this way, the air pool 16 communicates with the outside air through the ventilation holes 8b and the slit 19b, so that the air in the air pool 16 can flow even in a high temperature atmosphere. Since the pressure is reduced by being discharged to the outside through the ventilation holes 8b, it is possible to prevent the outer case 1 and the molding resin 10 from being deformed due to the thermal expansion of the air in the air reservoir 16.
Further, as shown in FIG. 5D, by securing the length L from the bottom of the slit 19b to the bottom of the outer case (for example, 2 mm or more), the creepage distance from the product surface of the current transformer 100 to the winding 13 can be determined. Since it can be secured, as compared with the case where the outer case 1 is provided with the ventilation holes 21a or 21b so that the winding 13 of the coil 12 shown in the bottom view (a) and the side view (b) of FIG. 8 is exposed. , High withstand voltage characteristics can be obtained.

1 Outer case 2 Outer case inner cylinder 3 Outer case outer cylinder 4 Lead wire insertion part 5 Lead wire lead part 6 Winding lead part 7a, 7b, 7c, 7d Notch shape 8a, 8b Vent 9 Gate (for filling resin) )
10 Molding resin 11 Lead wire 12 Coil 13 Winding 14 Case for accommodating magnetic core 15 Magnetic core 16 Air pool 17 Mold (upper mold)
18 mold (bottom)
19a, 19b Slit portion 20 Gate position 21a, 21b Simple ventilation hole example (when withstand voltage characteristics cannot be obtained)
100 current transformer and zero-phase current transformer

Claims (4)

A coil wound around an annular magnetic core having high relative permeability characteristics is housed in a case having a bottom surface and a double cylindrical wall, and a heat-fluidized molding resin is poured into the case from a molding die injection port. A current transformer or zero-phase current transformer that is pressure-molded integrally with the coil.
The case is a groove having a notch shape on the side surface of the filling region of the wall, or a groove of the wall, in at least one wall of the double cylindrical wall in the molding resin filling region separated from the injection port by a predetermined value or more. A current transformer or a zero-phase current transformer, which comprises a cylindrical vent hole having an open slit on the filling region side. The current transformer or zero-phase current transformer according to claim 1, wherein the groove having the notch shape has at least one tip portion in its cross section, and the angle leading to the tip portion is an acute angle. .. The current transformer according to claim 2, wherein the cross section of the groove having the notch shape includes the tip portion inclined in a direction facing the flow direction at the time of injection of the molding resin. Zero-phase current transformer. The slit of the cylindrical vent hole is in the direction from the top surface of the vent hole toward the bottom surface, and the depth thereof is deeper than the depth at which the molding resin is filled at the position of the vent hole and is predetermined from the bottom surface of the vent hole. The current transformer or current transformer or zero-phase current transformer according to claim 1, wherein the current transformer is shallow as long as it has the above length.

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