JP2901739B2 - Transformer - Google Patents

Description

The present invention relates to a transformer suitable for use as a power transformer for a cycloconverter.

(Prior Art) A circulating current type cycloconverter using this type of transformer is disclosed, for example, in Japanese Patent Application Laid-Open No. 63-186563. This will be described with reference to FIG. A three-phase AC power supply, 2 is a three-phase transformer including a power supply winding 3 (primary winding), a positive group winding 4 and a negative group winding 5 (all are secondary windings), and 6 is a thyristor 7 A positive group converter with a phase bridge connection, 8 is a negative group converter with a thyristor 9 connected in a three-phase bridge, and 10 and 11 are circulating current limits connected between the positive and negative DC output terminals of both converters 6 and 8. Reactor 12 is a load connected between the neutral points of both reactors 10 and 11. In such a cycloconverter, when a gate signal of a predetermined pattern is applied to the gates of the thyristors 7 and 9 of the converters 6 and 8, the output between the positive group converter 6 and the negative group converter 8
Between the output terminal and between the load 12 terminals, voltage e _op waveform indicated by a bold line in FIG. 7, e _on and e _o is obtained. here
e _o is the average value of e _op and e _on . Incidentally, the thin line the output voltage waveform of the three-phase AC power source 1, a dotted line indicates a fundamental wave component of the voltage e _op, e _on and e _o. 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 applied to the gate of the thyristor.

In such a cycloconverter, the positive half-wave current i _op of the load current i _o as shown in FIG. 8 is supplied from the thyristor 7 of positive group converter 6, the negative half-wave current i _on the negative group converter 8 are supplied from the thyristor 9, of which, t2-t3 is the i _op as a converter 6 when examples
During the period in which the thyristor 7 is forward-biased as shown by the period, the current is also in the forward direction and performs the forward conversion function, and even after the thyristor 7 shifts to the reverse bias state as shown by the period t3-t4. The reverse conversion function is performed during a period in which the current continues to flow in the forward direction. During the period in which one converter 6 performs the forward conversion and reverse conversion functions, the other converter 8 is in a standby state for preventing passage of current. However, although such a standby state is formed every half cycle, since the voltage actually includes harmonics as shown in FIG. 7, the standby state is formed between the converters 6 and 8 via the reactors 10 and 11. A circulating current flows. Only a half-wave current flows through the positive group winding 4 and the negative group winding 5 of the transformer 2, whereas the power winding 3 has the same ampere turns of both the positive and negative group windings 4 and 5. Since the full-wave current flows, if the current capacity of the positive or negative group winding is 1, the current capacity of the power supply winding 3 is approximately is necessary.

In the cycloconverter shown in FIG. 9, the positive group converter includes first and second positive group converters 6a and 6b, and the negative group converter includes the first and second negative group converters 8a and 6b.
a, 8b, in which the three-phase AC voltage applied to each converter has a phase difference of 30 degrees between the first and second converters. This is an improved circuit in which pulse modulation becomes thinner and high-frequency components are reduced. Normally, the converter portion having the configuration shown in FIG. 6 is called a 6-pulse bridge configuration, and the converter portion shown in FIG. 9 is called a 12-pulse bridge configuration.

(Problems to be Solved by the Invention) Transformer used in the cycloconverter shown in FIG.
13 is configured as shown in FIG. FIG. 10 shows only one iron leg 14 of the tripod iron. This leg 14 has a first positive group converter 6a and a first group for the negative group converter 8a.
Of the positive group winding 15a and the first negative group winding 16a, and the second positive group winding 15a for the second positive group converter 6b and the negative group converter 8b.
b and a second negative group winding 16b, a first power supply winding 17a arranged to be tightly coupled with the first positive and negative group windings, and a second positive and negative group winding 16b. And a second power supply winding 17b, which is arranged in a tight magnetic coupling relationship. First and second
Power supply windings 17a and 17b are connected in parallel and three-phase connected to the power supply windings wound around the other two legs, and the first positive group winding 15a is also connected to the other two legs. And the other windings 15b, 16a and 16b are similarly connected to the windings wound on the other two legs, respectively. Are connected in three phases.

A three-phase transformer used as a power supply transformer in a conventional 12-pulse bridge configuration cycloconverter is, as described above, for one phase of a three-phase winding, two positive group windings per leg. And two negative group windings and two further power supply windings are provided concentrically. Therefore, if the load 12 is three-phase, the number of converters must be increased from four to twelve and three-phase transformers must be three. Increasing the number of three-phase transformers to three causes an increase in manufacturing cost and an increase in installation space, and furthermore, the core volume is greatly increased, so that there is a problem that no-load loss, particularly, iron loss increases. Such an increase in no-load loss goes against the intent of adopting a cycloconverter, which attempts to reduce energy consumption by using a variable speed control system for the operation of the induction motor.

Therefore, an object of the present invention is to provide a power transformer connected to a cycloconverter to supply a three-phase alternating current from a cycloconverter having a 12-pulse bridge configuration to a three-phase load by using two iron cores. As a result, it is an object of the present invention to provide a transformer that can reduce no-load loss, can be reduced in size and weight, and can reduce manufacturing cost and installation space.

[Constitution of the Invention] (Means for Solving the Problems) The transformer according to the present invention is a transformer in which the first and second positive group converters and the first and second negative group converters are configured as 12 pulse bridges. A power transformer for a phase output cycloconverter, comprising: a first and a second iron core having three legs; a positive group winding, a negative group winding, and a power supply winding; For each leg of the iron core, three of said positive group windings connected to said first positive group converter of each of the three phases;
Three negative group windings and three power supply windings connected to the first negative group converter of each three phase are provided, and each of the legs of the second iron core is provided with a three-phase winding. Three of the positive group windings connected to the second positive group converter of each phase, three of the negative group windings connected to the second negative group converter of each phase of three phases, and 3 The power supply windings, and
And in each of the second iron cores, the three power supply windings provided on each leg are connected in parallel with each other, and then connected in a three-phase manner, and the three positive group windings provided on each leg are respectively connected to the three windings. To form three three-phase windings by three-phase connection over the three legs, and to form three three-phase windings by three-phase connection of the three negative group windings provided on each leg over the three legs. The windings of the first and second cores are formed in a different manner from each other so as to form a phase difference between the first and second cores.

(Operation) This transformer is used as a power transformer for a cycloconverter that supplies three-phase AC power to a three-phase load.
To apply a three-phase AC voltage to each phase of a three-phase (three) cycloconverter, six positive group and negative group windings are allocated per one-phase cycloconverter, and the power supply winding is a winding circuit. One is assigned to a pair of positive group and negative group windings in order to make the impedance the same between the positive and negative groups, and of these windings, the first positive, negative group and power supply winding are One three-leg core (first core) is configured as a single transformer that is magnetically coupled to each other, and the second positive, negative group, and the power supply winding also have one three-leg core. (2nd iron core) is comprised as an independent transformer. Although a transformer having such a configuration has the same function as having three three-phase transformers, only two iron cores are required, and as a result, the core yoke is two per core in the case of a three-leg iron core.
Where three are required, a total of six is required, but in the present invention only four are required, and the core volume is reduced accordingly.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 5 (A) and (B). As shown in FIG. 5 (A), in this embodiment, a three-legged first iron core 21 constituting a first transformer 20A has three legs 22-24 and a space between the legs 22-24. At the upper and lower ends thereof. FIG. 2 shows the winding structure of the one leg 22. As shown in FIG. 2, the three first positive group windings Xpu , Ypu, Zpu are arranged in the axial direction, and three first power supply windings Ua, Ub, Uc are similarly arranged on the outer periphery thereof, and three negative group windings Xnu, Ynu, Znus are placed and each 3
The windings are arranged concentrically. The same winding arrangement is applied to the other two legs 23 and 24. FIG. 1 shows the relationship between each leg and the windings arranged in this case. In FIG. 1, Xpv to Zpv and Xpw to Zpw are leg 2 respectively.
The first positive group windings provided at 3, 24, Xnv to Znv, Xnw to Znw
Are the first negative group windings Va-Vc, Wa provided on the legs 23, 24, respectively.
WWc are first power supply windings provided on the legs 23 and 24, respectively. FIG. 3 shows the overall configuration of a three-phase cycloconverter using the first transformer 20A and the second transformer 20B as power supplies. The second transformer 20B is configured exactly the same as the first transformer 20A shown in FIGS. 1, 2 and 4, and differs only in the form of the three-phase connection as described later. Third
In the figure, reference numeral 26 denotes a three-phase induction motor having three-phase loads, for example, three-phase stator windings X, Y, and Z corresponding to star-connected three-phase X, Y, and Z, respectively. AC voltage is applied to the lines from three sets of 12-pulse bridge-configured cycloconverters 27X, 27Y, 27Z, one set corresponding to one phase. Each set of cycloconverters has the same configuration as the first and second positive group cycloconverters 6a and 6b and the first and second negative group cycloconverters 8a and 8b shown in FIG. That is, 6aX, 6
aY, 6aZ and 6bX, 6bY, 6bZ are first and second positive group converters respectively corresponding to the stator windings 26X, 26Y, 26Z corresponding to the three phases, that is, X, Y, Z phases, on the motor 26 side. , 8aX, 8aY, 8aZ and 8
bX, 8bY, 8bZ are first and second negative group converters corresponding to the stator windings 26X, 26Y, 26Z, respectively. The connection relationship between such converters and the first and second transformers 20A and 20B will be described. FIG. 4 shows a three-phase AC power supply and a first transformer 20.
The connection relationship between the first positive and negative group windings of A and the power supply winding and the first positive and negative group converter is shown. First, three power supply windings U provided on the same leg 22 of the first iron core 21 are provided.
a, Ub, and Uc are connected in parallel and connected to the U-phase of the three-phase U, V, and W phases of the three-phase AC power supply 1, and three power supply windings provided on the legs 23 are provided.
Va, Vb, and Vc are connected in parallel and connected to the V phase of the three-phase AC power supply 1, and the three power supply windings Wa, Wb, and Wc provided on the legs 24 are connected in parallel to connect the three-phase AC power supply 1. While being connected to the W phase, the three sets of parallel windings are three-phase connected, for example, star-connected as a whole. On the other hand, U, V, W distributed on three legs 22-24
The three first positive group windings Xpu to Xpw and the three first negative group windings Xnu to Xnw corresponding to the respective phases are respectively connected in a three-phase connection, for example, in a star connection, and each of the first windings corresponding to the X phase. The first positive group windings Ypu to Ypw and the first negative group corresponding to the Y phase, which are connected to the positive group converter 6aX and the first negative group converter 8aX, and are also distributed and arranged on the three legs 22 to 24. The group windings Ynu to Ynw are star-connected, respectively, and connected to the first positive group converter 6aY and the negative group converter 8Y corresponding to the Y phase.
Z-phase corresponding first positive group windings Zpu to Z
The pw and the first negative group windings Znu to Znw are star-connected, respectively, and connected to the first positive group converter 6aZ and the first negative group converter 8aZ corresponding to the Z phase.

The connection between each positive and negative group winding Xpu to Znw of the second transformer 20B and the second positive and negative group converters 6bX, 8bX to 6bZ, 8bZ is the same as that of the first transformer 20A. But the second transformer 20B
The three-phase connection of the power supply windings Ua to Uc, Va to Vc, and Wa to Wc is a delta connection different from that of the first transformer 20A. Due to the difference in the three-phase connection, the first and second transformers 20
A phase difference of 30 degrees occurs between the output voltages of the windings A and 20B.

As a result of such a connection configuration, a three-phase AC voltage having a phase difference of 30 degrees is applied to the first positive and negative group converters 6aX to 8aZ and the second positive and negative group converters 6bX to 8bZ of the cycloconverter, This allows the stator windings 26X, 26
A three-phase AC voltage is applied to Y and 26Z from a cycloconverter, and the frequency is varied by controlling gate signals to thyristors 7 and 9 constituting each converter.

The transformer of this embodiment used in a cycloconverter for applying a three-phase AC voltage to a three-phase load conventionally has three transformers as shown in FIG. Two transformers 20A and 20B, that is, two cores 21 may be used, while three independent cores 28 are required. 5A and FIG. 5B, the volume of the core is compared with the conventional example using the dimensions shown (in this case, the thickness of the core is set to 1 for convenience).

The volume V (three volumes) of the conventional iron core is represented by the following equation.

V = 3 {W (2A + 2h) -4wh} = 6WA + 6Wh-12wh On the other hand, the volume V 'obtained by combining the two cores 21 of this embodiment is expressed by the following equation.

V '= 2W (2A + 3h) -12wh = 4WA + 6Wh-12wh As is apparent from the difference between V and V', it is understood that the volume of the iron core of this embodiment is smaller by 2WA in volume. That is,
In the case of a three-legged iron core, two irons are owned per three, so three irons will have a total of six iron cores. However, in the present invention, only four iron cores are required, and the core volume is reduced accordingly. If the material and the magnetic flux density of the iron core are the same, the no-load loss in the iron core is proportional to the volume of the iron core. In addition, since the no-load loss often occurs in the shaded portion of the yoke portion of the iron core in the drawing, the no-load loss is further reduced in the present embodiment in which the number of the yoke portions is reduced as compared with the related art. In addition, the material cost can be reduced as the core volume decreases, and the number of man-hours for assembling the iron core can be reduced to about 2/3, so that the manufacturing cost can be significantly reduced and the installation space for the iron core also decreases to about 2/3. .

In the above embodiment, the three-phase connection of the power supply winding is made different to obtain a phase difference of 30 degrees between the first and second transformers. The aspect is the same,
The mode of the three-phase connection of the positive and negative group windings may be different between the two transformers, for example, a star connection in the first transformer and a delta connection in the second transformer. Good. Furthermore, although the winding arrangement of the above embodiment is a concentric arrangement in which the power supply winding is interposed between the positive group winding and the negative group winding in the radial direction of the leg, the present invention is not limited to this. May be coaxially arranged between the positive group winding and the negative group winding in the axial direction of the leg.

[Effect of the Invention] As described above, the present invention is used as a power supply transformer connected to a cycloconverter for supplying a three-phase load to a three-phase load from a 12-pulse bridge configuration cycloconverter. And a transformer that can be composed of two iron cores. As a result, a transformer that can reduce no-load loss, can be reduced in size and weight, and can reduce manufacturing cost and installation space. Can be provided.

[Brief description of the drawings]

1 to 5 relate to an embodiment of the present invention, in which FIG. 1 shows the overall correspondence of the windings of a first transformer and FIG. 2 shows one leg of the transformer. , FIG. 3 is a connection diagram of the cycloconverter, FIG. 4 is a connection diagram specifically showing a part of the cycloconverter in FIG. 3, and FIG. ) Is a front view of the core of the transformer, FIG. 5 is a front view of the conventional iron core, FIG. 6 is a connection diagram of a general cycloconverter in the case of a single-phase load, and FIG. Voltage waveform diagram, FIG. 8 is a time chart showing voltage and current waveforms, FIG. 9 is a connection diagram of a general cyclo converter having a 12 pulse bridge configuration, FIG.
The figure shows the winding configuration of one leg of the transformer used in the cycloconverter shown in FIG. In the figure, 20A and 20B are first and second transformers (first and second iron cores), 21 is an iron core, 22 to 24 are legs, 26 is an induction motor, 6aX to 6
bZ is the first and second positive group converters, 8aX to 8bZ are the first and second negative group converters, Xpu to Zpw are positive group windings, Xnu to Znw are negative group windings, and Ua to Wc are power supply windings Line.

Claims (2)

(57) [Claims] 1. A transformer for a power supply of a three-phase output cycloconverter in which a first and a second positive group converter and a first and a second negative group converter are configured as a 12-pulse bridge, wherein three legs are provided. And a positive group winding, a negative group winding, and a power supply winding. The first core of each of three phases is provided for each leg of the first core. Three positive group windings connected to the positive group converter, three negative group windings connected to the first negative group converter of each of three phases, and three power supply windings For each leg of the second iron core, three positive group windings connected to the second positive group converter of each three-phase, and the second negative winding of each three-phase. Providing the three negative group windings and the three power supply windings connected to the group converter, and in each of the first and second cores: The three power supply windings provided on the legs are connected in parallel with each other and then connected in three phases, and the three positive group windings provided on each leg are connected in three phases across the three legs. Three three-phase windings are formed, and the three negative group windings also provided on each leg are three-phase connected to each of the three legs to form three three-phase windings. A transformer, wherein the three-phase connection of the power supply windings is changed so as to generate a phase difference between a power supply winding of a first iron core and a power supply winding of a second iron core. 2. A power transformer for a three-phase output cycloconverter in which the first and second positive group converters and the first and second negative group converters are configured as a 12-pulse bridge, wherein three legs are provided. And a positive group winding, a negative group winding, and a power supply winding. The first core of each of three phases is provided for each leg of the first core. Three positive group windings connected to the positive group converter, three negative group windings connected to the first negative group converter of each of three phases, and three power supply windings For each leg of the second iron core, three positive group windings connected to the second positive group converter of each three-phase, and the second negative winding of each three-phase. Providing the three negative group windings and the three power supply windings connected to the group converter, and in each of the first and second cores: The three power supply windings provided on the legs are connected in parallel with each other and then connected in three phases, and the three positive group windings provided on each leg are connected in three phases across the three legs. Three three-phase windings are formed, and the three negative group windings also provided on each leg are three-phase connected to each of the three legs to form three three-phase windings. The form of the three-phase connection of the positive and negative group windings is changed so as to produce a phase difference between the positive and negative group windings of the first core and the positive and negative group windings of the second core. A transformer characterized by the following.