JPS622448B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a current transformer suitable for installation within a terminal cover of a power meter.

BACKGROUND ART Generally, when measuring load current amount or load power amount, a method is adopted in which a current transformer is connected to one of the load lines and the current flowing through the current transformer is detected.

When measuring the amount of electric power per electric power consumer, as shown in Figure 1, a power meter 4 for transaction is installed on a distribution line 2 on a utility pole 1 and a power meter 4 installed at the door of a consumer 3. They are connected by a multi-core drop-in cable 5, and the locations where the load line is exposed as a single wire are the distribution line branch point a, the under-eaves branch point b, and the branch point inside the terminal cover 6 of the transaction electricity meter. Since the current transformer is limited to three locations c, the current transformer installation location is also limited to one of the above branch points.

However, distribution line branch point a and under-eaves branch point b
Since the distance from the electricity meter for transaction 4 is long, wiring work is required, and there are also disadvantages such as reduced noise resistance and surge resistance. Therefore, it is considered convenient to install the current transformer at a branch point of the lead-in cable 5' within the terminal cover 6 of the watt-hour meter 4 or the multi-core cable 7 on the load side.

As shown in FIGS. 2 and 3, a conventional current transformer 8 has a toroidal-shaped iron core 11 and an insulated wire evenly wound around the annular iron core 11 in a main body case 10 having a load wire through hole 9. The protective resistor 15 is housed in a protective resistor housing protrusion 14 that is connected to the main body case 10 and is housed in a protective resistor housing protrusion 14 . This protective resistor prevents dielectric breakdown of the coil 12 due to the high voltage induced in the coil when the secondary side of the current transformer becomes open. 16. Reference numeral 17 denotes a bush for protecting the lead wire extraction portion, which protrudes in a direction perpendicular to the load wire through hole 9.

Problems with the Prior Art It is practically impossible to install a conventional current transformer having the above-described structure inside the terminal cover of a power meter. That is, the possible space in which the current transformer can be installed inside the electricity meter terminal cover 6 is the hatched part A in Figs. 4 and 5, but the length of the single wire branching at this part is short, and Since both ends are restricted by the terminal fittings of the terminal box 18 and the cable lead-in portion of the terminal cover 6, it is not possible to widen the distance between the single wires.

Moreover, the types and dimensions of the multi-core cables 5' and 7 that are drawn into each component inside the watt-hour meter are restricted by JJS standards, etc., and current transformers cannot withstand large load currents of 100 amperes or more. In order to maintain linear output characteristics without saturation, the amount of iron core and copper of the coil are required to be above a certain value, and therefore there is a limit to the miniaturization of the current transformer.

Purpose of the Invention An object of the present invention is to solve the above-mentioned problems of the conventional current transformer and to provide a current transformer that can be installed in a limited space inside the terminal cover of a power meter. It is something.

Composition of the Invention The present invention provides a current transformer in which a ring-shaped magnetic core and a coil wound around the core are housed in a main body case having a through hole through which a load wire is passed, and in which the coil is wound eccentrically or split. , a current transformer in which the longitudinal cross-sectional shape of the main body case differs depending on its circumferential position.

The present invention also includes a current transformer in which a coil protection resistor is housed in a resistor housing part that protrudes in a direction parallel to the load line in a part of the main body case, and a lead wire connected to the coil is parallel to the load line. This includes a current transformer drawn out in the direction of the current.

Embodiments of the Invention The illustrated embodiments will be described in detail below.

6 to 8 show a plan view, a vertical cross-sectional view, and a perspective view of the current transformer 20 of the present invention. Inside the main body case 22, which has a load line through hole 21 in the center, there is a thin and wide laminated layer. An annular magnetic core 25 having an iron core 23 covered with an iron core case 24 is housed. This annular magnetic core consists of an annular portion 25a and a straight portion 25b,
The annular portion 25a is provided with an eccentric coil 26 in which an insulated wire is eccentrically wound such that the thickness increases as the distance from the straight portion 25b increases.

The outer surface portion of the main body case 22 in which the linear portion 25b of the annular magnetic core 25 is housed is a flat surface 22a, and the thickness B of that portion is thinner than the thickness C of the portion that accommodates the thick portion of the eccentric coil 26. ing. This thin part has a protrusion 22b extending downward (Fig. 7).
are arranged in series, and a protective resistor 27 is arranged therein so as to be located in a plane orthogonal to the load line through hole 21. In addition, the protrusion 22 is inserted through the bush 28 attached to the lower end surface (FIG. 7) of the protrusion 22b.
A coil 26 and a protective resistor 27 are connected in parallel between the terminals of the lead wire 29 inserted into the lead wire 2b.

Note that epoxy resin or other resin 30 is cast into the remaining space inside the main body case 22, and the annular magnetic core 2
5. The coil 26 and the main body case are integrally fixed.

In the current transformer 20 of the present invention having such a configuration, as shown in FIGS. 9 and 10, one single wire 7a branched from the load-side multi-core cable 7 is installed inside the terminal cover 6 of the watt-hour meter 4. The lead wire 29 is arranged to pass through the load wire through hole 21, and a load measuring device 19 is connected to the other end of the lead wire 29 and used for load measurement and the like.

When a current flows through the load wire 7a, the annular magnetic core 25 is excited by the magnetic force generated around the wire.
A current flows through the coil 26 wound around this.

There is a proportional relationship between the load current and the coil current, which is determined by the number of windings and the magnetic properties of the magnetic core. In order to improve the conversion accuracy of the coil, it is necessary to have a large number of turns, and in order to perform calculation control with the electronic circuit built into the load measuring device 19, it is necessary to extract a predetermined amount of current value. The conversion ratio (winding ratio) is determined taking this into consideration.

In the embodiment of the present invention, since the coil is wound eccentrically, the necessary winding ratio can be secured even when the coil is arranged in a limited space. In addition, if the cross-sectional area of a ring-shaped magnetic core is not constant, the magnetic permeability will be determined by the portion of the minimum cross-sectional area, and the magnetic properties will deteriorate. Since it is an area, its magnetic properties will not deteriorate. Note that even if the cross-sectional shape of the annular magnetic core differs, it has almost no effect on its magnetic properties, so in the present invention, the wall thickness of the current transformer can be reduced by using a thin, vertically elongated magnetic core. are doing. Of course, when selecting the shape of this annular magnetic core, its inner diameter, outer diameter, and height are determined by taking into account the geometrical shape of the winding machine jig.

As mentioned above, in the current transformer of the present invention, the annular magnetic core is provided with a straight part, and the coil wound around this is an eccentric coil. The space within the meter terminal cover where the current transformer can be installed can be used effectively.

In other words, since a part of the main body case is made thin, it can be arranged to avoid collision with the inner surface of the adjacent terminal cover or another single wire of the multi-core cable. If a flat surface is formed in a part of the main body case, it can be placed along the inner surface of the flat terminal cover or the surface of an adjacent single wire.

In addition, if the protective resistor storage part is made to protrude below the main body case and the direction in which the lead wires are pulled out is made to match the direction in which the load wires pass through, the efficiency of use of the current transformer installation space will be further improved. .

Modifications of the Invention FIGS. 11 and 12 respectively show modifications of the annular magnetic core and coil according to the invention.

In FIG. 11, uneven thickness coil parts 26a and 26b are formed by dividing the annular magnetic core 25 into two parts, and a thin part B where there is no coil winding is formed between them. The thickness is considerably thinner than the thickness of the portion C made thicker by dividing the coil, and the load wire insertion hole 21 is oval. Therefore, the outer diameter of the main body case 22 can also be reduced in the vicinity where the portion where the coil is not wound is accommodated.

In Fig. 12, a toroidal magnetic core 25 is used, and a coil 26 is formed by extremely eccentric winding.The thickness of the thin part B is much thinner than that of the thick part C. There is.

Effects of the Invention As is clear from the above description, according to the present invention, a thin wall portion is formed in a part of the main body case by split winding or eccentric winding of a coil, or a combination of these and a non-circular annular magnetic core. At the same time, the protective resistor storage section is protruded below the main case, so
When applied to a power meter, by arranging the thin wall portion at the narrowest location, it can be easily set inside the terminal cover.

In addition, the space in which the current transformer can be installed inside the terminal cover is generally vertically long, so it adapts to the shape, making it easy to place the current transformer and draw out the lead wires. Since the magnetism of the wire can be determined, wiring mistakes can be prevented.

In addition, the load line through hole can be oval regardless of the external shape of the case body, so it can be installed with high space efficiency when using a load line with an oval cross section or when detecting load current.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of how a transaction electricity meter is installed, and FIG. 2 is a cross-sectional view illustrating a conventional current transformer.
FIG. 3 is a vertical cross-sectional view thereof, and FIG. 4 is a front view illustrating the space in which a current transformer can be installed in a transaction electricity meter.
FIG. 5 is a cross-sectional view thereof, FIGS. 6 to 8 are plan views, longitudinal sectional views, and perspective views showing embodiments of the current transformer of the present invention, and FIGS. 9 and 10 are current transformers of the present invention. Front view and side view showing an example of how the device is installed, Figures 11 and 12
The figures are explanatory diagrams of main parts showing modified examples of the current transformer of the present invention. 4... Electricity meter for transaction, 5, 5', 7... Multi-core cable, 6... Terminal cover, 8, 20... Current transformer, 9, 21... Load line through hole, 10, 22... …
Main body case, 11... Iron core, 12, 26... Coil, 13, 30... Resin, 14, 22b... Protective resistor storage protrusion, 15, 27... Protective resistor, 1
6, 29...Lead wire, 19...Load measuring device.

Claims (1)

[Scope of Claims] 1. In a current transformer in which a ring-shaped magnetic core and a coil wound around the core are housed in a main body case which has a load line through hole and is connected with a protective resistance storage part, the coil is divided. A modification characterized in that a thin wall portion is formed in a part of the main body case by winding or eccentric winding, and the protective resistor storage portion is provided protrudingly below the main body case continuously from the thin wall portion. Flushware. 2. The current transformer according to claim 1, wherein the annular magnetic core is composed of a thin and wide iron core. 3. The current transformer according to claim 1 or 2, wherein a part of the outer surface of the main body case is a flat surface. 4. The current transformer according to any one of claims 1 to 3, wherein the annular magnetic core consists of an annular portion and a straight portion. 5. According to any one of claims 1 to 4, the lead wire whose one end is connected to the coil and the protective resistor is drawn out in a direction parallel to the load wire through hole. current transformer.