JPS5835361B2 - Double ratio current transformer consisting of multiple current transformers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a double ratio current transformer constructed by connecting in series a plurality of double ratio current transformers each having a tap on a secondary coil.

It is well known to use two current transformers having the same current transformation ratio connected in series with a primary coil and a secondary coil.

For example, two current transformers with a current transformation ratio of 10015A, an error class of 1.0, and a rated load of 20VA are connected in series with both primary coils 1.1' and secondary coils 2 and 2' as shown in Figure 1. For example, current ratio 10015A error class 1.0, rated load 4
A 0VA current transformer is obtained.

However, if the current transformer is a double ratio current transformer having a tap on the secondary coil 3 as shown in FIG. 2, the series connection of the secondary coils is not as simple as in the case of a single ratio current transformer.

Conventionally, two double ratio current transformers CTI, Cr2, with equal current transformation ratios of 200-10015A, are used.
1) When used with 20015A, as shown by the solid line, the winding end terminal 1 of the secondary coil 3 of the first current transformer CTI is connected in series.
1 to the winding start terminal 2 of the secondary coil 3' of the second current transformer CT2, and the secondary coil 30 winding start terminal 1 kl
2) When using 10015A, connect the load zb between the winding end terminal 11 of the secondary coil 30 and the tap terminal 2 of the secondary coil 3' as shown by the dotted line. It is necessary to connect the load zb between the tap terminal 1 of the secondary coil 3 and the winding end terminal 21 of the secondary coil 3'.

This operation is more complicated than the case of a single double ratio current transformer as shown in Figure 2, and may cause incorrect connections, so it is not normally done to connect double ratio current transformers in series. Not yet.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks and to provide a double ratio current transformer that allows switching of the current ratio without any particular difficulty.

Therefore, a current transformer with better characteristics can be obtained using standard products.

In order to achieve this object, the present invention provides a terminal plate and simplifies the arrangement of the terminals as in the case of a single current transformer.

According to the present invention, this purpose is to connect a plurality of current transformers in series by connecting the winding end terminal of each current transformer to the tap terminal of the next stage current transformer, and to and the tap terminal of the secondary coil of the first stage current transformer,
This is achieved by leading out the winding end terminals of the secondary coil of the final stage current transformer as secondary external terminals.

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 4 shows an embodiment in which two double ratio current transformers according to the present invention are connected in series, and the terminal 11 at the end of the 30th turn of the secondary coil of the first current transformer Connect 2 to the tap terminal 2 of the secondary coil 3' of the second current transformer CT2, 1 to the winding start terminal 2 of the secondary coil 3' of the second current transformer CT2, and The terminal board 4 uses the tap terminal 1 of the secondary coil 3 as the winding end terminal 2 and the winding end terminal 21 of the secondary coil 3' of the second current transformer CT2 as the winding start terminal, tap terminal 2, and winding end terminal l, respectively. Pull it out.

For example, current transformation ratio 200-10015 connected like this
When using the A current transformers CT1 and CT2 at 20015A, if you connect the load zb between the terminals 1 and 1, the secondary current will be 1-load zb one terminal l one terminal 21-
The current flows through the circuit of the secondary coil 3' of the second current transformer CT2 and one terminal 2.

In this case, no current flows through the secondary coil 3 of the first current transformer CT1, so the characteristics are the same as when only the second current transformer CT2 is used, and the transformation described at the beginning is the same. There appears to be no advantage in improving the characteristics by connecting two flow vessels in series.

However, the characteristics of a double ratio current transformer are limited by the tap with the smaller current transformation ratio, so for example, 200-10015A,
When using a 1.0 class, 20VA current transformer with a current transformation ratio of 20015A, only one current transformer is sufficient for 1.0 class 40 V
Since it has the characteristic A, there is no particular need to connect two current transformers in series.

Next, when using 10015A, if you connect the load zb between the terminals 2 and l, the secondary current will be connected to the terminal 2 - load zb - terminal l - terminal 21 - the second current transformer CT2. Secondary coil 3' one terminal 2 to 21 terminal IJII! - i1 flows through the secondary coil 3 - terminal 1 k20 circuit of current transformer CT1, so in this case CT1 and CT2 are connected in series and the rated load can be doubled.

When adding a third, fourth, etc. current transformer and connecting them in series, connect the winding end terminal of the secondary coil of each current transformer to the tap terminal of the secondary coil of the next stage current transformer in sequence. Then, the winding start terminal of the secondary coil of the final stage current transformer is set to the external terminal 1, and the tap terminal of the secondary coil of the first stage current transformer is set to the external terminal 2. The end terminal of the secondary coil of the device can be pulled out as the external terminal l.

Additionally, additional current transformers can be added one after the other in this way, or by connecting multiple current transformers interconnected as one unit as shown in Figure 4. You can go.

FIG. 5 shows the connection when a third current transformer CT3 is added.

In this case, when using the terminal with more current (1 as the winding start terminal), no current flows through the secondary coils 3 and 3' of the first and second current transformers CT1 and CT2, which are in an open state. Become.

Depending on the current transformer's size, current transformation ratio, etc., the voltage induced between the secondary terminals in an open state may become extremely high, potentially threatening insulation.

In this case, as shown in FIG. 5, between the winding start terminal and the winding end terminal of the open coils 3, 3'
121) or between the tap terminal and the winding end terminal (1 to 2-IA), or between the winding start terminal and the tap terminal (2kl
It is preferable to insert a known current transformer secondary open circuit protection device 5 into 2 and 2).

As is clear from the above description, according to the present invention, individual requirements can be easily met by connecting standard current transformers as in the present invention, instead of manufacturing special products according to specifications. can be met.

Furthermore, in use, since the terminal arrangement is similar to that of a single current transformer, there is no risk of incorrect connection.

[Brief explanation of the drawings] Figure 1 is a wiring diagram for connecting two single-ratio current transformers in series, Figure 2 is a wiring diagram for a double-ratio current transformer with a tap on the secondary coil, Fig. 3 is a wiring diagram when two current transformers shown in Fig. 2 are connected in series, Fig. 4 is a wiring diagram of an embodiment of the present invention,
FIG. 5 is a wiring diagram of another embodiment of the present invention. 1, 1', 111 primary coil, 2, 2', 3
, 3', 3'/: Secondary coil, 4 two-terminal board, 5: Secondary open circuit protection device.

Claims (1)

[Claims] 1. In a device in which a plurality of double current transformers with equal current transformation ratios having tap terminals in the secondary coil are connected to form one double ratio current transformer, the winding of each current transformer is Connect multiple current transformers in series by connecting the end terminal to the tap terminal of the next stage current transformer, and connect the winding start terminal of the secondary coil of the last stage current transformer and the first stage current transformer. Double ratio current transformation consisting of a plurality of current transformers, characterized in that the tap terminal of the secondary coil of the current transformer and the winding end terminal of the secondary coil of the final stage current transformer are respectively derived as secondary external terminals. vessel. 2. In the current transformer according to claim 1, when connecting the secondary coils of each current transformer in series, a terminal of the secondary coil that is not connected to a terminal of another current transformer or led out as a secondary external terminal A double ratio current transformer comprising a plurality of current transformers, characterized in that a secondary circuit protection device is connected between the current transformer and the other terminal of the secondary coil of the current transformer.