JPH06112071A - Cycloconverter transformer - Google Patents

Abstract

PURPOSE:To enhance a cycloconverter transformer in detection sensitivity to current failure by a method wherein a cycloconverter of 12-pulse bridge constitution is composed of two three-phase transformers, and the number of positive and negative group winding sets which a current transformer provided to power supply winding of the three-phase transformer is assigned in detection is limited to four sets. CONSTITUTION:Three positive group windings 33a to 33c, three negative group windings 34a to 34c, and three power supply windings 32a to 32c are provided to each leg of a first and a second iron core, 30 and 31, each provided with three legs, the three power supply windings 32a to 32c wound on the different legs of the first iron core 30 are connected in delta connection to form three sets of three-phase windings, the three power supply windings 32a to 32c wound on the different legs of the first iron core 31 are connected in star connection to form three sets of three-phase windings, one set of three-phase winding wound on the first core 30 and another set wound on the second core 31 are connected in parallel, and the residual sets of three-phase windings are subjected to the above process. A current transformer 38 is provided to a feeding line common to the parallel circuits concerned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cycloconverter transformer suitable for use as a power source for a circulating current type cycloconverter.

[0002]

2. Description of the Related Art A conventional structure of a circulating current type cycloconverter using a transformer of this type will be described with reference to FIG.
In this figure, 1 is a three-phase AC power supply, 2 is a three-phase transformer consisting of a power supply winding (primary winding) 3, a positive group winding 4 and a negative group winding 5 (all are secondary windings), Reference numeral 6 is a positive group converter in which a thyristor 7 is connected in a three-phase bridge, 8 is a negative group converter in which a thyristor 9 is connected in a three-phase bridge, 10
Reference numerals and 11 are circulating current limiting reactors connected between the positive and negative DC output terminals of both converters 6 and 8, and 12 is a load connected between the neutral points of both reactors 10 and 11. In such a cycloconverter, when a gate signal having a predetermined pattern is applied to the gates of the thyristors 7 and 9 of the converters 6 and 8, between the output terminals of the positive group converter 6, between the output terminals of the negative group converter 8 and the load 12 respectively. Between the terminals of, the voltage eop, eo of the waveform shown by the thick line in FIG.
n and eo are obtained. Where eo is eop and e
It is the average value of on. The thin line indicates the output voltage waveform of the three-phase AC power supply 1, and the dotted lines indicate the respective voltages eop, eon and eo.
The fundamental wave component of is shown. In this way, the cycloconverter is used as a frequency conversion circuit that directly converts the power supply frequency to an arbitrary frequency within a lower range by controlling the gate signal supplied to the power supply of the thyristor.

In the cycloconverter shown in FIG. 4, the positive group converter is composed of first and second positive group converters 6a and 6b.
And the negative group converter is composed of first and second negative group converters 8a and 8b. Then, the transformer 13 includes the first and second three-phase power supply windings 17a and 17b.
And two sets of three-phase positive group windings 15a corresponding to these,
15b and two sets of three-phase negative group windings 16a and 16b, and a three-phase AC voltage is applied to each converter in a relationship having a phase difference of 30 degrees between the first and second converters. The circuit is configured so that the harmonic components are reduced more than that shown in FIG. Normal,
The converter portion having the structure shown in FIG. 2 is called a 6-pulse bridge structure, and the converter part shown in FIG. 4 is called a 12-pulse bridge structure.

A three-phase transformer 1 used as a power transformer in a cycloconverter having a 12-pulse bridge structure.
3 is configured as shown in FIG. FIG. 5 shows only one core leg 14 of the tripod core. First on this leg 14
First positive group winding 15a and first negative group winding 16a for the positive group converter 6a and negative group converter 8a, and second positive group winding 15b and the first positive group winding 15b for the second positive group converter 6b. The second negative group winding 16b and the first power source winding 17a arranged so as to be closely magnetically coupled to the first positive and negative group windings.
And a second power supply winding 17b arranged to be closely magnetically coupled to the second positive and negative group windings. The first and second power supply windings 17a and 17b are connected in parallel and three-phase connected with the power supply windings wound on the other two legs, and the first positive group winding 15a is also connected to the other. Three-phase connection is made between the first positive group winding wound around the two legs of the same, and the remaining windings 15b, 16a, and 16b are also wound around the other two legs. Three-phase connection is made with the winding.

The transformer having the above-mentioned structure is used as a load 12
If it is applied to the case of three phases, three three-phase transformers are required as shown in FIG. In FIG. 6, when the current transformer 18 is provided on the input side of the power supply winding for protection of the transformer, as shown in the figure, the power supply winding of each transformer is connected in parallel to the parallel circuit. One common power supply line.

In addition to this method, there is a method using a three-phase transformer as shown in FIG. In FIG. 7, 1 is a three-phase AC power source, 19 and 20 are three sets of positive group windings 15a and 15
b, 15c and three sets of negative group windings 16a, 16b, 16c and three sets of power supply windings 17a, 17b, 17c. FIG. 8 shows the winding arrangement of only one leg of this three-phase transformer. FIG. 8 corresponds to the configuration of FIG. 5 with a set of positive group winding 15c and negative group winding 17c added.

The power supply windings of such three-phase transformers 19 and 20 are connected as shown in FIG. That is, in FIG. 9, the power supply windings 17a and 17b of the first three-phase transformer 19 are
17c are connected in parallel and then connected in a triangular shape,
The power supply windings 17a, 17b, 17c of the three-phase transformer 20 are connected in parallel and then star-connected, and these three-phase connection windings are connected in parallel between the first and second transformers 19, 20. After that, the three-phase AC power source 1 is connected. The current transformer 18 for protecting the transformer is arranged in a common power supply path for each parallel circuit as shown in the figure.

[0008]

By the way, of the two types of the 12-pulse bridge configuration cycloconverter described above, the configuration shown in FIG. 6 basically requires three transformers, whereas the configuration shown in FIG. Since No. 7 is composed of two transformers, no load loss is reduced, and it is small and lightweight.

However, in the case of FIG. 6, one set of current transformers (one set of three-phase connection is one set) corresponding to four sets (three-phase connection is one set) of windings including positive group and negative group. 7) is used, only one set of current transformers is used in FIG. 7 corresponding to the six sets of windings including the positive and negative groups. In this case, in the worst case, when all the windings have a simultaneous accident,
In the current transformer, four sets of winding currents flow in the case of the configuration of FIG. 6, and six sets of winding currents flow in the case of the configuration of FIG. 7. Therefore, a fault on the secondary side of the transformer occurs. The current detection sensitivity of the latter is about 2/3 that of the former. This is a drawback that the application of the method having the configuration of FIG. 7 is limited to a system having a small capacity, for example, although it has the above-mentioned excellent points.

Therefore, an object of the present invention is to provide a cycloconverter for a cycloconverter having a 12-pulse bridge structure consisting of two three-phase transformers, which can improve the detection sensitivity of a fault current on the secondary side of the transformer. The purpose is to provide a transformer.

[0011]

The cycloconverter transformer according to the present invention has three positive group windings and three negative group windings on each leg of the first and second iron cores having three legs. Line and 3
Three power supply windings are provided, and the three power supply windings of the first iron core are three-phase connected, for example, triangularly connected to form three sets of three-phase windings, and the three power supply windings of the second iron core are connected. A positive group in which three pairs of three-phase windings are formed by connecting the power supply winding to a type different from the three-phase wiring of the power supply winding of the first iron core to form three sets of three-phase windings and provided on each leg of the same iron core. The windings are three-phase connected to form three sets of three-phase windings, and the negative group windings provided on each leg of the same iron core are also three-phase connected to form three sets of three-phase windings. A first set of power windings of the first iron core and a first set of power windings of the second iron core, which are three-phase connected, are connected in parallel, and similarly, a second set of power windings of the first iron core is connected. The wire and the second set of power supply windings of the second iron core are connected in parallel, and the third set of power supply windings of the first iron core and the third set of power supply windings of the second iron core are connected in parallel. Connected to each parallel circuit and connected to each common power supply line. Characterized in that a vessel.

[0012]

According to the 12-pulse bridge type cycloconverter consisting of the transformer having such a configuration, assuming that one set of three-phase connection windings has three sets of three-phase connection power supply windings for one transformer. 3 corresponding to each phase of each set of three-phase wiring
Each of the terminals serves as a common power supply path for power supply windings connected in parallel, and nine common power supply paths are formed as a whole, and a current transformer is provided for each of the common power supply paths. As a result, the number of windings that one set of current transformers bears is 2 for the power supply windings and 4 for the number of positive and negative windings, and the number of transformers is as small as 2 as shown in FIG. This means that not only the same advantages as the conventional one can be obtained, but also the fault current detection sensitivity of the current transformer is as high as the conventional one shown in FIG.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. The cycloconverter transformer of this embodiment is
A first transformer including a first iron core 30 having three legs 30a and a second transformer core 31 also having three legs 31a.
And a second transformer including. In the first iron core 30, each leg 30a has three power windings 32a to 32c,
Three positive group windings 33a to 33c and three negative group windings 34
a-34c are provided, and these three power supply windings are three-phase connected, for example, triangularly connected, between three different legs, and thereby three sets of three-phase connected (three-phase connected three A single power winding circuit is formed.

The second iron core 31 is also provided with the same windings and the same wire connections, but especially the first iron core 3
To generate a phase difference of 30 degrees for a winding current of 0,
A three-phase connection of a type different from that of the power supply winding of the first iron core 30, for example, a star connection is made. On the other hand, the three first positive group windings 32a provided on each leg of the first iron core are three-phase connected as in the conventional case, and the first three negative group windings 34a and the second
Positive and negative group windings 33b and 34b, third positive and negative group winding 3
Similarly, three-phase connection is made for 3c and 34c.

Further, in the power supply winding, the first set of power supply windings 32a of the first iron core 30 and the first set of power supply windings 32a of the second iron core 31 connected in three phases are connected in parallel. Is
Similarly, the second set of power supply windings 32b of the first iron core 30 and the second set
Second power supply winding 32b of the iron core 31 is connected in parallel, and a third power supply winding 32c of the first iron core 30 and a third power supply winding 32c of the second iron core 31 are connected. Are connected in parallel, and common power supply paths 35a to 35c (one set) and 36a to 36 for supplying power to the parallel circuit from the three-phase AC power supply 1.
c (1 set), 37a to 37c (1 set)
8 (one set) are provided.

According to the 12-pulse bridge type cycloconverter consisting of the transformer having such a structure, one set of three-phase connection windings is one transformer, one iron core 3
For 0 and 31, three sets of three-phase connection power supply windings are formed, and three terminals corresponding to each phase of each three-phase connection, that is, common power supply paths 35a to 35c (36a to 36c or 37a to
37c) is connected in parallel to the two sets of power supply windings 32a (32
b or 32c), a total of nine common power supply paths are formed, and a current transformer 38 is provided for each of them. As a result, one set of current transformers 38 bears two sets of windings for the power supply winding and four sets of positive and negative windings, and the number of transformers is as small as two. In addition to the same advantages as the conventional one shown in FIG. 6, the fault current detection sensitivity of the current transformer on the secondary side of the transformer is improved to about 1.5 times that in FIG. Means that there is an advantage in being high. Therefore, since the detection sensitivity of the fault current on the secondary side of the transformer is improved, a transformer for a 12 pulse bridge cycloconverter composed of two iron cores can be realized even for a large capacity cycloconverter that could not be applied in the past. Will be possible.

In the above construction, the power supply windings are three-phase connected between the different legs, but the three legs may be connected in the same leg.

[0018]

As described above, the present invention is used as a power supply transformer connected to a three-phase load in order to supply a three-phase alternating current from a cycloconverter having a 12-pulse bridge structure. It is suitable for, and can be composed of two iron cores. As a result, the detection sensitivity of the secondary side fault current is improved in the transformer in which the no-load loss is reduced and the size and weight can be reduced. It is possible to provide a transformer for a cycloconverter whose application range is expanded.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an overall connection relationship between windings of a transformer and a connection state of a current transformer according to an embodiment of the present invention.

[Fig. 2] Connection diagram of a general cycloconverter with a single-phase load

FIG. 3 is a voltage waveform diagram of each part in FIG.

FIG. 4 is a wiring diagram of a general cycloconverter having a 12-pulse bridge configuration.

5 is a diagram showing a winding configuration of one leg of a transformer used in the cycloconverter shown in FIG.

6 is a connection diagram of a three-phase cycloconverter using three sets of cycloconverters shown in FIG.

FIG. 7 is a wiring diagram of a three-phase cycloconverter having a method different from that of FIG.

8 is a diagram showing a winding configuration of one leg of a transformer used in the cycloconverter shown in FIG. 7.

FIG. 9 is a diagram showing an overall connection relationship between windings of the transformer of FIG. 7 and a connection state of current transformers.

[Explanation of symbols]

In the figure, 1 is a three-phase AC power supply, 30 is a first iron core, 31 is a second iron core, 32a to 32c are power supply windings, and 33a to 33c.
Is a positive group winding, 34a to 34c are negative group windings, and 35a to 37
c is a common power supply path, and 38 is a current transformer.

Claims (1)

[Claims] 1. A leg of each of the first and second iron cores having three legs is provided with three positive group windings, three negative group windings and three power source windings, and The three power windings of the iron core are connected in three phases to form three sets of three-phase windings, and the three power windings of the second iron core are connected to the three power windings of the first iron core. Three sets of three-phase windings that are different from the three-phase wiring are formed to form three sets of three-phase windings, and the positive group windings provided on each leg of the same iron core are three-phase connected to form three sets of three-phase windings. And the negative group windings provided on each leg of the same iron core are also three-phase connected to form three sets of three-phase windings, and the first set of three-phase connected iron core is the power source. The winding and the first set of power supply windings of the second iron core are connected in parallel, and similarly, the second set of power supply windings of the first iron core and the second set of power supply windings of the second iron core are connected. Are connected in parallel, and the third set of power windings of the first iron core and the second iron are further connected. A transformer for a cycloconverter, which is characterized by connecting a third set of power source windings in parallel with each other and providing a current transformer in each common power feeding path to each parallel circuit.