JPS5837685B2 - Manufacturing method of split type zero-phase current transformer - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement in a method for manufacturing a split zero-phase current transformer.

In general, a split-type zero-phase current transformer is constructed by assembling a pair of semicircular arc-shaped split molds 1, 1 into an annular shape, as shown in FIG.

Each split mold 1 has a semi-circular arc-shaped iron core 2 around which a conducting wire is wound, surrounding a shield case 3, 3, which is housed in a semi-circular molded case 4, and a synthetic resin 5 is placed in the gap between the cases 40 and 3. The iron cores 2, 2 exposed from the molded case 4 and the shield cases 3, 3 are brought into contact with each other and assembled in a ring shape.

This split type zero-phase current transformer is widely used as an earth leakage sensing device for detecting electric leakage, and is installed so as to surround existing wiring in hotels, theaters, factories, etc.

Therefore, in order to use the split type zero-phase current transformer for the above applications,
There is a need for a device that is highly sensitive and can sense minute ground leakage currents, does not malfunction due to external induction, and has stable sensitivity characteristics even when there are changes in the environment of the installation site, season, temperature, etc.

For this reason, the present inventor previously proposed a method for manufacturing a split zero-phase current transformer using a set of semicircular arc-shaped molded cases.

This method involves enclosing a pair of conductive wires in a shield case on the outside of a separately wound annular core, then housing them in a set of semi-circular arc-shaped molded cases arranged in an annular manner, and then placing a ring between the cases. The cases are fixed with an intervening plate having a predetermined thickness in between and spaced apart from each other for a certain period of time. Then, after injecting and solidifying the synthetic resin into the case, the intervening plate is removed and the gap between the two cases ( In this method, the annular core and shield case are cut and separated along the location where the intervening plate is removed, and then the cut surfaces of the core and shield case are polished.

According to this method, the annular core and the annular shield case are cut and formed, so the precision of each split mold is high.Moreover, since the core and shield case protrude from the mold case, when the split molds are assembled, The iron core and shield case are in good suppressing contact with each other.

Therefore, in the split zero-phase current transformer obtained by this method, even if the mold case expands or contracts due to temperature changes, the cores do not separate from each other, and stable sensitivity characteristics can be obtained.

However, this method requires a large number of steps and has poor workability because an intervening plate is sandwiched between a pair of molded cases and these are fixed.

Furthermore, since the synthetic resin is injected with the intervening plates sandwiched between them, the resin tends to leak from between the mold case and the intervening plates.

Moreover, since the intervening plate must be removed after the resin is injected, there is a problem in that the work requires time and effort, such as applying a mold release agent to the intervening plate in advance.

For this reason, the inventor of the present invention conducted intensive research on a method of manufacturing a split zero-phase current transformer as an annular integral structure instead of using a structure in which the molded case is divided into two parts, and as a result, the following was discovered. did.

In other words, when the annular mold case, iron core, and shield case that are assembled as one body are cut diametrically into two halves and the divided surfaces are polished, if this is done while cooling, the soft mold case will be deeply polished. As a result, the hard core and the shield case are in a state of protruding from the molded case, and it has been found that it is possible to obtain a divided zero-phase current transformer similar to the case using the aforementioned divided molded case.

The present invention has been developed with this point in mind; by polishing the divided surfaces while cooling, it is possible to use a molded case with an annular integral structure during assembly and manufacturing, thereby improving assembly work efficiency. The purpose of the present invention is to provide a split type zero-phase current transformer that can perform

The method of the present invention will be explained below with reference to illustrative examples.

First, as shown in Figure 2, 80 N i - 5 M
The outer periphery of an annular core 2' made of a magnetic material with high magnetic permeability such as -Fe alloy is insulated, and a pair of conducting wires 6 are connected to this core 2'.
, 6 are wound, and these conducting wires 6, 6 are further coated with insulation.

In this case, each conducting wire 6, 6 is wound around the iron core 2' in a semicircular arc shape, and the conducting wires 6, 6 are wound around the iron core 2' in two opposing locations.
A non-conductor portion is formed in which no wire is wound.

Next, a pair of annular shield cases 3', 3' are vertically enclosed around the outer periphery of the iron core 2' around which the conductive wires 6, 6 are wound, with a gap between them.

These shield cases 3', 3' are made of a high permeability magnetic material such as 45Ni-Fe alloy, and have an iron core 2/l:J''
- This is to prevent receiving electromagnetic force from the outside.

Next, the iron core 2' surrounded by shield cases 3', 3'
is housed in the mold case 4'.

As shown in FIG. 3, this molded case 4' is of an integral structure having an annular core accommodating portion 4a, and terminals 7 are attached to one side thereof.

After that, a flexible resin such as silicone resin is filled in the gap between the molded case 4' and the non-conducting part where the conductive wires 6, 6 are not wound (cutting point in the subsequent process), and then epoxy resin is filled in the case 4'. A hardening resin such as resin is injected into the gaps between the mold case 4' and the shield cases 3', 3' and solidified, and after the lid 8 is closed, the iron core 2 and the shield cases 3', 3' are placed in the mold case 4'. Fix 3'.

This state is as shown in FIG.

The molded case 4', shield case 3', and core 2' that are integrally fixed in this way are cut in the diametrical direction and divided into two parts, and a pair of divided molds 1 and 1 are formed as shown in FIG. form.

In this case, the cutting point is a non-conductive wire portion where the conductive wires 6, 6 are not wound.

In addition, each split type 1 has a semicircular arc shape, and semicircular arc shield cases 3 and a semicircular arc iron core 2 around which a conducting wire 6 is wound.
The mold case 40 has a structure in which the gap between the mold case 40 and the mold case 40 is filled with synthetic resin 5.

Next, the 10-divided surface 1a of each divided mold is polished while being cooled.

This polishing method includes, for example, wet puff polishing.
By polishing with this method, the splitting surface 4b of the mold case 40 can be adjusted to the splitting surface 3a of the shield cases 3, 3 and the iron core 2.
The shield cases 3, 3 and the iron core 2 protrude from the molded case 4 by several microns to more than ten microns by being polished deeper than the mold case 2a.

Moreover, the shield cases 3, 3 and the dividing surfaces 3a, 2 of the iron core 2
After polishing, a is polished in a direction perpendicular to the axis of the iron core 2 and is not inclined, so that when the split dies 1 and 1 are combined, the split surfaces 2a and 3a abut against each other completely.

In other words, if the split surface 1a of the split mold 1 is polished without cooling, the iron core 2 and shield cases 3, 3 will expand due to frictional heat.
Polished in a thermally expanded state.

Therefore, when cooled after polishing, the iron core 2, shield case 3,
3 shrinks in the opposite direction, and the dividing surfaces 2a and 3a become the mold case 4.
This results in poor contact between the polished surfaces when assembling the split molds 1 and 10.

Moreover, since the outer and inner circumferential parts of the iron core 2 have different expansion amounts, the outer circumferential part shrinks greatly after polishing, and the dividing surface 2a of the iron core 20 is inclined.
This results in poor contact between the dividing surfaces 2a and 3a during assembly.

On the other hand, when polishing is performed while cooling the divided surface 1a as in the method of the present invention, the iron core 2 and the shield cases 3, 3 do not undergo thermal expansion and do not contract after polishing.

Moreover, the molded case 4 made of synthetic resin is softer than the metal core 2 and shield cases 3, 3.
This area is deeply polished, and as a result, the iron core 2 and the shield cases 3 protrude from the mold case 4.

Therefore, according to the method of the present invention, it is possible to obtain a divided zero-phase current transformer with the same high precision as when a divided molded case is used.

Further, since the integral molded case 4 is used, the number of parts is small and assembly is easy, and the resin does not leak to the outside when the synthetic resin is injected.

In this case, the mesh roughness of the emery paper used for wet puff polishing is preferably 400 to 120 mesh, and the rotation speed of the puff board is preferably 250 to 350 rpm.

Next, a split type zero-phase current transformer is manufactured by the method of the present invention, and the output voltage E is determined by the change in the secondary load resistance RL.

And changes in residual voltage EL were measured.

The results are shown in FIG.

In this case, the dimensions, material, and polishing conditions of the split type zero-phase current transformer are as shown in Table 1 below.

Further, in the figure, a curve a1 shows a change in the output voltage, and a curve a2 shows a change in the residual voltage.

On the other hand, a split type zero-phase current transformer was manufactured by polishing the split mold without cooling it, and its electrical characteristics were measured in the same manner as in the above embodiment, and the results are also shown in FIG.

In this case, the curve b1 shows the change in the output voltage with respect to the change in the secondary load resistance, and the curve b2 shows the change in the residual voltage.

From this result, it was confirmed that the split type zero-phase current transformer according to the present invention has a high output voltage, a low residual voltage, and excellent electrical characteristics.

As explained above, according to the method of the present invention, an integrated molded case can be used, so the number of parts can be reduced, the number of assembly steps can be reduced, assembly can be made easier, and the synthetic resin to be injected can be prevented from leaking. can.

Moreover, the obtained split type zero-phase current transformer has excellent electrical characteristics, high precision, and various other remarkable effects.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a split type zero-phase current transformer showing an embodiment of the method of the present invention, Fig. 2 is an exploded cross-sectional view showing the assembled state of the zero-phase current transformer before cutting, and Fig. 3 is a plan view of the molded case, Fig. 4 is a perspective view showing the assembled state of the zero-phase current transformer before cutting, and Fig. 5 shows the electrical characteristics of the split type zero-phase current transformer according to the present invention. It is a characteristic diagram. 1... Split type, 2... Iron core, 2a... Split surface, 3
... Shield case, 3a... Divided surface, 4... Mold case, 4b... Divided surface, 7... Terminal, 8...
··lid.

Claims (1)

[Claims] 1. After surrounding the outer side of the annular iron core around which the conducting wire is wound, a shielding case is housed in an integrated molded case, the molded case is filled with a synthetic resin to unite them, and then the above-mentioned molded After cutting and dividing the case, the annular core, and the shield case in the diametrical direction to form a pair of semicircular arc-shaped split dies, the cut surfaces of the split dies are polished while being cooled to cut the annular core and the shield case. A method for manufacturing a split type zero-phase current transformer, characterized in that a surface thereof protrudes beyond a cut surface of the molded case.