JPH065449A - Current transformer - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To reduce the size of the gap between the discharge electrodes and the shape of the discharge electrodes to reduce the overall configuration in the case where the secondary open circuit voltage is high. [Structure] Split cores 2 and 3 obtained by splitting an annular core 1 into two
, And each of the two divided secondary windings 4 and 5 is wound, and terminal fittings are connected to both ends of these two divided secondary windings 4 and 5, respectively, and the two divided secondary windings 4 and 5 are connected in series. A secondary winding is formed by connecting them, and a discharge electrode is provided on a terminal fitting to which both ends of either one of the split secondary windings 4 and 5 are connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a secondary winding in which a split secondary winding is wound around each of split iron cores obtained by splitting an annular iron core into two, and these two split secondary windings are connected in series. The present invention relates to a split type current transformer configured by forming a wire.

[0002]

2. Description of the Related Art Generally, a low-impedance measuring instrument or a relay is connected to both terminals of a secondary winding of a current transformer, and a secondary current induced by a primary current is supplied to these devices. I am trying to supply it. In this case, if the terminals of the secondary winding are opened due to a failure of the above-mentioned equipment, etc., the secondary current will stop flowing, and all the primary current will be consumed by the core excitation. An excessive voltage (hereinafter referred to as a secondary open circuit voltage) is induced between both terminals. Due to this excessive secondary open circuit voltage, the insulation of the above-mentioned equipment may be destroyed, or the iron loss of the current transformer itself may rapidly increase, causing a temperature rise and thermal breakdown of the insulating material.

Conventionally, there are two methods for protecting against such an excessive secondary open circuit voltage. First, one method is to connect a protection device that causes discharge when the secondary open circuit voltage reaches a set voltage between both terminals of the secondary winding. However, this configuration has a drawback that the manufacturing cost becomes high because a special protection device must be provided.

As another method, particularly in a split type current transformer, a discharge electrode is attached to terminal fittings connected to both ends of a secondary winding, and when the secondary open circuit voltage exceeds a set voltage. There is a configuration in which discharge is performed via the discharge electrode. This structure will be described with reference to FIGS. As shown in FIG. 3, split secondary windings 4 and 5 are respectively wound around two split iron cores 2 and 3 which form the annular iron core 1. As shown in FIGS. 4 and 5, terminal fittings 6, 7, 8 and 9 are connected to both ends of these two split secondary windings 4 and 5, respectively. A surface 1a on which the two split iron cores 2 and 3 contact each other is a split surface.

Then, the terminal metal fitting 7 and the terminal metal fitting 8 are connected via the crossover wire 10, whereby the two divided secondary windings 4 and 5 are connected in series to form the secondary winding 11. There is. In addition, the split iron cores 2 and 3 and the split secondary windings 4 and 5 are
It is molded by the molding material 12. Here, a relay terminal fitting 13 is provided on the side of one of the split cores 2, and the relay terminal fitting 13 and the terminal fitting 9 of the split secondary winding 5 are connected via a crossover wire 14. ing.
As a result, the terminal fitting 6 and the relay terminal fitting 13 serve as both terminals of the secondary winding in which the split secondary windings 4 and 5 are connected in series. Lead wires 15 and 16 connected to an instrument, a relay, etc. are connected to the terminal fitting 6 and the relay terminal fitting 13.

Here, the terminal fitting 6 and the relay terminal fitting 1
3, discharge electrodes 17 and 18 made of metal plates are attached. The gap size between the discharge electrodes 17 and 18 is such that when the secondary open circuit voltage exceeds the set voltage, both electrodes 1
The discharge is set to occur between 7 and 18.
According to this configuration, since the discharge electrodes 17 and 18 are simply provided, no special protection device is required, and the manufacturing cost is reduced.

[0007]

However, in the above-mentioned conventional configuration, in the type in which the secondary open circuit voltage is considerably high (for example, the current transformer having the rated secondary current of about 1 A), the voltage at the time of generating the discharge is large. That is, since the set value of the secondary open circuit voltage becomes high, it is necessary to increase the size of the gap between the discharge electrodes 17 and 18 and the shape of the discharge electrodes 17 and 18 themselves. For this reason, there is a drawback that the installation space for the terminal fittings 6 and 13 becomes large, which in turn enlarges the overall configuration of the current transformer.

Therefore, an object of the present invention is to provide a current transformer capable of reducing the size of the gap between the discharge electrodes and the shape of the discharge electrodes even when the secondary open circuit voltage is high, thereby reducing the overall structure. To provide the vessel.

[0009]

In the current transformer of the present invention, split secondary windings are respectively wound around two split iron cores forming an annular core, and the split secondary windings are respectively provided on both ends of these split secondary windings. In a current transformer formed by connecting terminal pieces to each other and connecting the two divided secondary windings in series, a discharge electrode is provided on the terminal piece to which both ends of one of the divided secondary windings are connected. There is a feature in the place.

[0010]

Even when the secondary open circuit voltage of the secondary winding becomes high, the voltage induced in any one of the two divided secondary windings connected in series is The magnitude is 1/2 or less of the secondary open circuit voltage. The present invention has been made paying attention to this point.

According to the above means, a discharge electrode is provided on the terminal fitting to which both ends of one of the split secondary windings are connected,
Since the discharge is generated between the discharge electrodes, even if the secondary open circuit voltage is high, when the discharge is generated between the discharge electrodes, the voltage applied to the discharge electrodes is 1 / second of the secondary open circuit voltage. The size is 2 or less, and the voltage is considerably low. Therefore, the gap size between the discharge electrodes can be reduced, the shape of the discharge electrodes themselves can be reduced, and the configuration of the entire current transformer can be reduced. In addition, since it is not necessary to provide the relay terminal fitting, the relay terminal fitting and the connecting wire can be eliminated, the number of parts can be reduced, and the manufacturability can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The configuration of the present embodiment other than the terminal portion is the same as the configuration described in FIG. 3 showing the conventional configuration, and the same portions are denoted by the same reference numerals. That is, the split secondary windings 4 and 5 are respectively wound around the two split iron cores 2 and 3 forming the annular iron core 1. These divided iron cores 2 and 3 and divided secondary windings 4 and 5 are
It is molded by the molding material 12. still,
A surface 1a where the two split iron cores 2 and 3 contact each other is a split surface. Also, two split secondary windings 4 and 5
The number of turns of each is set to the same number of turns.

At both ends of the two split secondary windings 4 and 5, as shown in FIGS. 1 and 2, terminal fittings 2 are respectively provided.
1, 22, 23 and 24 are connected. These terminal fittings 21, 22, 23, 24 are bolts 21a, 22a,
23a, 24a and these bolts 21a, 22a, 23a,
Nuts 21b, 22b, 23b, 2 screwed into 24a
4b and. Then, the terminal fitting 22 and the terminal fitting 23
By connecting and via the crossover wire 25, the two split secondary windings 4 and 5 are connected in series to form a secondary winding 26. In this case, the connection terminals 25a, 25a at both ends of the connecting wire 25 are fastened and fixed to the bolts 22a, 23a of the terminal fittings 22, 23 by nuts 22b, 23b, respectively.

Further, the terminal fitting 21 and the terminal fitting 24 are
Secondary winding 2 in which two split secondary windings 4 and 5 are connected in series
6 terminals. These terminal fittings 21 and terminal fittings 2
4, lead wires 27 and 2 connected to an instrument or relay, etc.
8 are connected to each other. In this case, lead wire 2
The connection terminals 27a and 28a of the terminals 7 and 28 are connected to the bolts 21a and 24a of the terminal fittings 21 and 24 and the nut 21 respectively.
It is fastened and fixed by b and 24b.

Discharge electrodes 29 and 30 are provided on the terminal fittings 21 and 22 to which both ends of one of the two divided secondary windings 4 and 5, for example, the divided secondary winding 4 are connected. Has been. Each of the discharge electrodes 29 and 30 is made of a metal plate, and substantially semicircular discharge portions 29a and 30a are formed at opposite ends thereof. Each discharge electrode 2
9 and 30 are bolts 2 of the terminal fittings 21 and 22, respectively.
The nuts 21b and 22b are inserted into the nuts 1a and 22a.
It is fixed by tightening.

In this case, the size of the gap between the discharge electrodes 29 and 30 is such that when the secondary open circuit voltage exceeds the set voltage,
It is set so that a discharge is generated between the discharge parts 29a and 30a of both electrodes 29 and 30.

However, according to the above configuration, the discharge electrodes 29 and 30 are provided on the terminal fittings 21 and 22 to which both ends of the one split secondary winding 4 are connected, and the discharge is performed between the discharge electrodes 29 and 30. Since the voltage is generated, even if the secondary open circuit voltage is high, the voltage applied to each of the discharge electrodes 29 and 30 at the time of discharging is approximately half the secondary open circuit voltage.
For this reason, the voltage applied to the discharge electrodes 29, 30 is lowered, so that the gap size between the discharge electrodes 29, 30 can be reduced and the shape of the discharge electrodes 29, 30 itself can be reduced. Therefore, the overall structure of the current transformer can be reduced in size.

Further, since the discharge voltage when the discharge is generated between the discharge electrodes 29 and 30 is lowered, the discharge energy is also reduced accordingly, and the damage to the parts due to the discharge can be suppressed and reduced.

By the way, the conventional structure (see FIGS. 4 and 5)
In the above, since the discharge is generated between both terminals of the secondary winding 11 in which the divided secondary windings 4 and 5 are connected in series, in order to accurately set the gap size between the discharge electrodes, It is necessary to collect and arrange the discharge electrodes on the side of one of the split iron cores 2 and 3. Therefore, in the conventional configuration, the relay terminal metal fitting 13 is provided on the side of the split iron core 2, and the relay terminal metal fitting 13 and the terminal metal fitting 9 of the split secondary winding 5 are connected to each other by the crossover wire 1.
4, the discharge electrodes 17 and 18 are attached to the relay terminal fitting 13 and the terminal fitting 6, respectively.

On the other hand, in the present embodiment, since the discharge is generated between the terminals of one of the split secondary windings 4, it is not necessary to provide the relay terminal fitting, and the relay terminal is not required. It is possible to eliminate the need for metal fittings and crossovers, reduce the number of parts, and significantly improve manufacturability.

In the above embodiment, after the secondary open circuit voltage is discharged, the number of turns of the divided secondary winding 4 in the discharging portion is half the number of turns of the entire secondary winding 26. Therefore, a current twice as high as the normal current flows into the split secondary winding 4 in the discharge part. This is due to the consideration of the overcurrent intensity of the secondary winding 26 as will be described below. No problem at all.

That is, the overcurrent strength of the secondary winding of the current transformer is
It is 40 times 1 second or more, which is the minimum condition recommended by the standard, and the service life at the time of secondary opening of the current transformer is 2 minutes 60 seconds since it has been conventionally set to 1 minute. On the other hand, since the temperature rise of the winding for a short time is obtained by the product of the square of the current density and the time, in the secondary winding having the same cross-sectional area, the current density can be restated as an overcurrent multiple. Therefore, 40 × 40 × 1> 2 × 2 × 60, that is, 1600> 240 and 240 ÷ 1600 = 0.15 As a result, the secondary open circuit condition of the present embodiment is that the temperature rise when the overcurrent intensity is maximum allowable. Is about 15% of
It turns out that there is no problem.

In the above embodiment, the discharge electrodes 29, 30 are provided on the terminal fittings 21, 22 on the side of the divided secondary winding 4, but the terminal fittings 23, 30 on the side of the other divided secondary winding 5 are arranged. Two
It is also possible to adopt a configuration in which a discharge electrode is provided on the No. 4. Further, although the number of turns of each of the two divided secondary windings 4 and 5 is set to be the same, it is needless to say that the number of turns may be set to be different.

[0024]

As is apparent from the above description, the present invention has a structure in which the discharge electrode is provided on the terminal fitting to which both ends of either one of the split secondary windings are connected, so that the secondary open circuit voltage is high. Also in this case, the gap size between the discharge electrodes can be reduced, the shape of the discharge electrodes can be reduced, and the overall structure of the current transformer can be reduced in size.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a plan view showing the vicinity of a terminal fitting and a discharge electrode.

[Fig. 2] Electric circuit diagram

FIG. 3 is a vertical sectional side view of the entire current transformer showing the conventional configuration.

FIG. 4 is a view equivalent to FIG.

FIG. 5 is a view corresponding to FIG.

[Explanation of symbols]

1 is an annular iron core, 2 and 3 are split iron cores, 4 and 5 are split secondary windings, 21, 22, 23 and 24 are terminal fittings, 26 is a secondary winding, 27 and 28 are lead wires, 29 and 30 Indicates a discharge electrode.

Claims (1)

[Claims] 1. A split secondary winding is wound around each of two split cores forming an annular core, and terminal fittings are connected to both ends of these split secondary windings, respectively, and
A current transformer comprising a plurality of divided secondary windings connected in series, wherein a discharge electrode is provided on a terminal fitting to which both ends of one of the divided secondary windings are connected.