Polyphase transformer and power conversion device

Abstract

To provide a polyphase transformer that can easily set the number of turns of a third winding to a second winding constituting a secondary side, and to provide a power converter that can generate two types of DC voltages.SOLUTION: A polyphase transformer 1 includes a first winding 11 on a primary side to which three-phase power is connected, and a second winding 12 and a third winding 13 that constitute a secondary side, and the first winding 11 is delta-connected while the second winding 12 and the third winding 13 are both star-connected with the same number of turns, and the second winding 12 and the third winding 13 have a common neutral point. A full-wave rectifier circuit 2 includes a neutral terminal 22 connected to a common neutral point Q of the second winding 12 and the third winding 13, in addition to output terminals of a positive terminal 21a and a negative terminal 21b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polyphase transformer for converting three-phase AC power to DC power, and to a power conversion device using this polyphase transformer. [Background technology]

[0002] The present inventors have proposed a multi-phase transformer for a power conversion device described in Patent Document 1 as a multi-phase transformer for converting three-phase AC power into DC power. This transformer has made it possible to reduce the size of the transformer by star-connecting both the second and third windings that make up the secondary side and by reducing the number of turns of the third winding compared to the second winding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-198776 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the number of turns in the third winding of the conventional multi-phase transformer mentioned above is √3-1 times that of the second winding, making it difficult to adjust and requiring skill to create the transformer. Also, while a voltage of 100 / 200V can be easily selected with a single-phase three-wire circuit, a DC / DC converter is required to obtain a different DC voltage with a DC power supply, making it difficult to change the voltage.

[0005] In view of these problems, the present invention aims to provide a multi-phase transformer that can achieve a simple turns ratio for the number of turns of the third winding relative to the second winding that constitutes the secondary side, and to provide a power conversion device that can generate two types of DC voltage. [Means for solving the problem]

[0006] In order to solve the above problem, the invention of claim 1 is a multi-phase transformer in which a first winding on a primary side to which three-phase power is connected and a second winding and a third winding constituting a secondary side are wound around a common iron core to convert three-phase power into DC power, and the multi-phase transformer outputs multi-phase AC power, The first winding is delta-connected or star-connected, while the second and third windings are both star-connected with the same number of turns, and the second and third windings have a common neutral point; The second winding has an R-phase winding portion, an S-phase winding portion, and a T-phase winding portion that generate voltages with phases that differ by 120 degrees, and the third winding has a U-phase winding portion that generates a voltage of opposite phase to the R-phase winding portion, a V-phase winding portion that generates a voltage of opposite phase to the S-phase winding portion, and a W-phase winding portion that generates a voltage of opposite phase to the T-phase winding portion; The second and third windings generate and output a total of six voltage phases, each with a phase difference of 60 degrees. This configuration makes it possible to obtain six-phase AC voltages with the same voltage value. Moreover, since the second and third windings have the same number of turns, there is no need to pay attention to the number of turns. Furthermore, full-wave rectification results in a 12-phase DC voltage, making it possible to obtain a DC voltage with small ripples.

[0007] The invention of claim 2 is the configuration of claim 1, further comprising fourth to seventh windings each having three winding portions for forming three phases, One winding portion of each of the fourth and fifth windings is branched and connected to an end of each winding portion of the second winding, and one winding portion of each of the sixth and seventh windings is branched and connected to an end of each winding portion of the third winding, one end of the first winding portion of the fourth winding is connected to an end of the S-phase winding portion of the second winding, and the first winding portion is wound around the iron core so as to be continuous with the R-phase winding portion of the second winding; the second winding portion of the fourth winding is wound around the iron core so that one end is connected to an end of the R-phase winding portion of the second winding and is continuous with the S-phase winding portion of the second winding; the third winding portion of the fourth winding is wound around the iron core so as to be continuous with the T-phase winding portion of the second winding, with one end connected to an end of the R-phase winding portion of the second winding; one end of the first winding portion of the fifth winding is connected to an end of the T-phase winding portion of the second winding, and the first winding portion is wound around the iron core so as to be continuous with the R-phase winding portion of the second winding; the second winding portion of the fifth winding is wound around the iron core so as to be continuous with the S-phase winding portion of the second winding, with one end connected to an end of the T-phase winding portion of the second winding; the third winding portion of the fifth winding is wound around the iron core so as to be continuous with the T-phase winding portion of the second winding, with one end connected to the end of the S-phase winding portion of the second winding; the first winding portion of the sixth winding is wound around an iron core continuous with the U-phase winding portion of the third winding, with one end connected to an end of the V-phase winding portion of the third winding; the second winding portion of the sixth winding is wound around the core so as to be continuous with the V-phase winding portion of the third winding, with one end connected to an end of the U-phase winding portion of the third winding; the third winding portion of the sixth winding has one end connected to an end of the U-phase winding portion of the third winding, and is wound around an iron core that is continuous with the W-phase winding portion of the third winding; the first winding portion of the seventh winding is wound around the iron core so that one end is connected to an end of the W-phase winding portion of the third winding and is continuous with the U-phase winding portion of the third winding; the second winding portion of the seventh winding is wound around the iron core so as to be continuous with the V-phase winding portion of the third winding, with one end connected to an end of the W-phase winding portion of the third winding; the third winding portion of the seventh winding is wound around the iron core so as to be connected at one end to an end of the V-phase winding portion of the third winding and to be continuous with the W-phase winding portion of the third winding; The fourth to seventh windings are wound with 0.36 times the number of turns of the second and third windings, The other end of each of the fourth to seventh windings is a secondary output terminal, and voltages of a total of 12 phases, each differing in phase by 30 degrees, are output. This configuration makes it possible to obtain 12-phase AC voltage with the same voltage value. Therefore, by full-wave rectifying it, a 24-phase DC voltage is obtained, making it possible to obtain a DC voltage with even smaller ripples.

[0008] A power conversion device according to the invention of claim 3 includes the multi-phase transformer according to claim 1 or 2 and a full-wave rectifier circuit that rectifies an output of the multi-phase transformer, The full-wave rectifier circuit is characterized by having a neutral terminal connected to the common neutral point of the second winding and the third winding, in addition to the output terminals of the positive and negative terminals. With this configuration, the terminals for outputting DC power include a neutral terminal in addition to a positive terminal and a negative terminal, so two types of DC voltages can be output, making it easy to change the DC voltage supplied to the load. [Effects of the Invention]

[0009] According to the present invention, it is possible to obtain a six-phase AC voltage with the same voltage value. Moreover, since the second winding and the third winding have the same number of turns, there is no need to pay attention to the number of turns. Furthermore, by performing full-wave rectification, it becomes a 12-phase DC voltage, making it possible to obtain a DC voltage with small ripples. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a wiring explanatory diagram showing an example of a multi-phase transformer and a power conversion device according to the present invention; [Figure 2] 2 is a vector diagram of the voltages generated on the secondary side of the multi-phase transformer of FIG. 1. [Figure 3] FIG. 10 is a wiring explanatory diagram showing another example of a multi-phase transformer and a power conversion device. [Figure 4] 4 is a vector diagram of the voltage generated by the polyphase transformer of FIG. 3, where (a) is an overall diagram and (b) is an explanatory diagram. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0016] The present invention will be described in detail below with reference to the accompanying drawings, in which:

[0017] Fig. 1 is a wiring diagram illustrating an example of a multi-phase transformer according to the present invention; 1 is a multi-phase transformer; 2 is a rectifier circuit; 3 is a three-phase power supply; and 10 is a power conversion device comprising the multi-phase transformer 1 and the rectifier circuit 2. The multi-phase transformer 1 has a first winding 11 that constitutes the primary side, a second winding 12 and a third winding 13 that constitute the secondary side, and has a primary side terminal 5 consisting of three terminals (Rin, Sin, Tin) and a secondary side terminal 6 consisting of six terminals (R, S, T, U, V, W).

[0012] Each of the first to third windings 11 to 13 has three winding portions (11a to 11c, 12a to 12c, 13a to 13c) to accommodate three-phase power. The first winding 11 is delta-connected, while the second winding 12 and the third winding 13 are star-connected, with the second winding 12 and the third winding 13 having the same number of turns. The neutral points are connected to each other and share a common neutral point Q. In this way, a six-phase transformer that outputs six-phase voltages is formed. The iron core 4 also has three iron core legs 4a, 4b, and 4c corresponding to the three phases. The turn ratio between the primary and secondary sides is set arbitrarily according to the DC voltage to be generated.

[0013] The rectifier circuit 2 has a positive terminal 21a and a negative terminal 21b that full-wave rectify and output a six-phase voltage, as well as a neutral terminal 22 connected to the neutral point Q on the secondary side of the multi-phase transformer 1.

[0014] Here, we will explain the relationship between the individual winding portions of the second winding 12 and the third winding 13. The first winding portion (R-phase winding portion) 12a having the R terminal of the second winding 12 and the first winding portion (U-phase winding portion) 13a having the U terminal of the third winding 13 are wound around the common core leg 4a in opposite directions. The second winding portion (S-phase winding portion) 12b having the S terminal of the second winding 12 and the second winding portion (V-phase winding portion) 13b having the V terminal of the third winding 13 are wound around the common core leg 4b in opposite directions. The third winding portion (T-phase winding portion) 12c having the T terminal of the second winding 12 and the third winding portion (W-phase winding portion) 13c having the W terminal of the third winding are wound around the common core leg 4c in opposite directions.

[0015] FIG. 2 shows a vector diagram of the voltage output from each of the secondary terminals 6 wound in this way. The voltages output from the three terminals R, S, and T of the second winding 12 correspond to the three-phase voltages input, and are three-phase voltages with a phase difference of 120 degrees from each other. Similarly, the voltages output from the three terminals U, V, and W of the third winding 13 are three-phase voltages with a phase difference of 120 degrees from each other. Since the windings of the second winding 12 and the third winding 13 are wound in opposite directions, voltages with a phase difference of 180 degrees are generated. As a result, the voltage output from the secondary side is a six-phase voltage, with each phase having the same voltage value but differing in phase by 60 degrees, as shown in Figure 2. When each of these voltages is full-wave rectified by the rectifier circuit 2, a 12-phase DC voltage is generated.

[0016] In this way, by star-connecting the second winding 12 and the third winding 13 on the secondary side with the same number of turns, it is possible to obtain a six-phase AC voltage with the same voltage value. Moreover, since the second winding 12 and the third winding 13 have the same number of turns, there is no need to pay attention to the number of turns. Furthermore, by performing full-wave rectification, a 12-phase DC voltage is obtained, making it possible to obtain a DC voltage with small ripples. Furthermore, since the output terminals include the positive terminal 21a, the negative terminal 21b, and the neutral terminal 22, two types of DC voltages can be output, making it easy to change the DC voltage supplied to the load.

[0017] FIG. 3 shows another example of a power conversion device 10. As shown in FIG. 3, the power conversion device 10 has a multi-phase transformer 1a and a rectifier circuit 2a. The number of windings of the multi-phase transformer 1a is significantly different from that of the above-described embodiment. The windings constituting the secondary side include a second winding 12, a third winding 13, a fourth winding 14, a fifth winding 15, a sixth winding 16, and a seventh winding 17. The number of turns of these windings is different from that of the second winding and the third winding, which have the same number of turns, and is 0.36 times that of the third winding. Similar to the first to third windings 11 to 13, the fourth to seventh windings 14 to 17 are also configured to have three winding portions (first to third winding portions) for forming three phases.

[0018] The following description will focus on the differences between the multi-phase transformer 1a and that shown in FIG. The first winding portion 14a of the fourth winding 14 has one end connected to the tip of the second winding portion (S-phase winding portion) 12b of the second winding 12, and is wound around the core leg 4a so as to be continuous and in phase with the first winding portion (R-phase winding portion) 12a of the second winding 12. The second winding portion 14b of the fourth winding has one end connected to the tip of the first winding portion (R-phase winding portion) 12a of the second winding 12, and is wound around the core leg 4b so as to be continuous and in phase with the second winding portion (S-phase winding portion) 12b of the second winding 12. The third winding portion 14c of the fourth winding has one end connected to the tip of the first winding portion (R-phase winding portion) 12a of the second winding 12, and is wound around the core leg 4c so as to be continuous and in phase with the third winding portion (T-phase winding portion) 12c of the second winding 12.

[0019] The first winding portion 15a of the fifth winding 15 has one end connected to the tip of the third winding portion (T-phase winding portion) 12c of the second winding 12, and is wound around the core leg 4a so as to be continuous and in phase with the first winding portion (R-phase winding portion) 12a of the second winding. The second winding portion 15b of the fifth winding 15 has one end connected to the tip of the third winding portion (T-phase winding portion) 12c of the second winding 12, and is wound around the core leg 4b so as to be continuous and in phase with the second winding portion (S-phase winding portion) 12b of the second winding 12. The third winding portion 15c of the fifth winding 15 has one end connected to the tip of the second winding portion (S-phase winding portion) 12b of the second winding 12, and is wound around the core leg 4c so as to be continuous and in phase with the third winding portion (W-phase winding portion) 12c of the second winding 12.

[0020] The first winding portion 16a of the sixth winding 16 has one end connected to the tip of the second winding portion (V-phase winding portion) 13b of the third winding 13, and is wound around the core leg 4a so as to be continuous and in phase with the first winding portion (U-phase winding portion) 13a of the third winding 13. The second winding portion 16b of the sixth winding 16 has one end connected to the tip of the first winding portion (U-phase winding portion) 13a of the third winding 13, and is wound around the core leg 4b so as to be continuous and in phase with the second winding portion (V-phase winding portion) 13b of the third winding 13. The third winding portion 16c of the sixth winding 16 has one end connected to the tip of the first winding portion (U-phase winding portion) 13a of the third winding 13, and is wound around the core leg 4c so as to be continuous and in phase with the third winding portion (W-phase winding portion) 13c of the third winding 13.

[0021] The first winding portion 17a of the seventh winding 17 has one end connected to the tip of the third winding portion (W-phase winding portion) 13c of the third winding 13, and is wound around the core leg 4a so as to be continuous and in phase with the first winding portion (U-phase winding portion) 13a of the third winding 13. The second winding portion 17b of the seventh winding 17 has one end connected to the tip of the third winding portion (W-phase winding portion) 13c of the third winding 13, and is wound around the core leg 4b so as to be continuous and in phase with the second winding portion (V-phase winding portion) 13b of the third winding 13. The third winding portion 17c of the seventh winding 17 is connected at one end to the tip of the second winding portion (V-phase winding portion) 13b of the third winding 13, and is wound around the core leg 4c so as to be continuous and in phase with the third winding portion (W-phase winding portion) 13c of the third winding 13.

[0022] Figure 4 shows a vector diagram of the voltage output from each secondary-side terminal 6 wound in this way. (a) is an overall view, and (b) is an explanatory view of a portion, showing the voltage vectors of each secondary-side winding relative to the neutral point Q. r4, s4, and t4 represent the output terminals of the fourth winding 14, r5, s5, and t5 represent the output terminals of the fifth winding 15, r6, s6, and t6 represent the output terminals of the sixth winding 16, and r7, s7, and t7 represent the output terminals of the seventh winding. As shown in FIG. 4(a), voltages of six phases in total are generated, consisting of three phases R, S, and T generated by the second winding 12 and three phases U, V, and W generated by the third winding 13. Voltages are branched off from each of these phases to generate voltages from the fourth to seventh windings, and a total of 12 phases of voltage are output.

[0023] Here, the reason why the number of turns of the fourth to seventh windings 14 to 17 is set to 0.36 times the number of turns of the second and third windings 12 and 13 will be explained. For example, if the DC output voltage VDC is 750V, The voltage V1 from the neutral point Q on the secondary side of the polyphase transformer 1a to the 12 output terminals is V1=VDC / √2=530.33V Then, when X, Y, and Z are set as shown in Figure 4(b), X=A·cos15°=512.26V Y=A·sin15°=137.26V Z=Y / tan60°=79.247V From these results, B=XZ=512.26-79.247=433.01V C=Y sin30°=137.26 sin30°=158.49V Therefore, B:C=433.01:158.49=1:0.366 So C is 0.366 times B. That is, the number of turns of the fourth to seventh windings is 0.366 times that of the second and third windings 12 and 13.

[0024] In this way, voltages of all 12 phases, each having the same voltage value but differing in phase by 30 degrees, are output from the 12 output terminals r4 to r7, s4 to s7, and t4 to t7 on the secondary side. Then, the voltage is rectified by the rectifier circuit 2a, whereby a 24-phase direct current is generated and output.

[0025] In this way, a 12-phase AC voltage with the same voltage value can be obtained, and by full-wave rectifying it, a 24-phase DC voltage can be obtained, making it possible to obtain a DC voltage with even smaller ripples.

[0026] In the above embodiment, the first winding 11 is delta-connected, but may be star-connected. Also, the secondary side of the multi-phase transformer 1, 1a is configured to output a 6-phase or 12-phase voltage, but if the secondary winding is configured to have a neutral pole, a neutral pole terminal can be provided even if the winding is in another form, making it possible to easily output two types of voltage. [Explanation of symbols]

[0027] 1,1a·· Multi-phase transformer, 2,2a·· Rectifier circuit (full-wave rectifier circuit), 10·· Power conversion device, 11·· First winding, 12·· Second winding, 13·· Third winding, 14·· Fourth winding, 15·· Fifth winding, 16·· Sixth winding, 17·· Seventh winding, 12a·· R-phase winding portion, 12b·· S-phase winding portion, 12c·· T-phase winding portion, 13a·· U-phase winding portion, 13b·· V-phase winding portion, 13c·· W-phase winding portion, 21a·· Positive terminal, 22b·· Negative terminal, 23·· Neutral terminal.

Claims

1. A multi-phase transformer that outputs multi-phase AC power by having a first winding on a primary side to which three-phase power is connected and a second winding and a third winding constituting a secondary side wound around a common iron core in order to convert three-phase power into DC power, the first winding is delta-connected or star-connected, while the second winding and the third winding are both star-connected with the same number of turns, and the second winding and the third winding have a common neutral point; The second winding has an R-phase winding portion, an S-phase winding portion, and a T-phase winding portion that generate voltages with phases that differ by 120 degrees, and the third winding has a U-phase winding portion that generates a voltage of opposite phase to that of the R-phase winding portion, a V-phase winding portion that generates a voltage of opposite phase to that of the S-phase winding portion, and a W-phase winding portion that generates a voltage of opposite phase to that of the T-phase winding portion, A multi-phase transformer characterized in that the second winding and the third winding generate and output voltages of a total of six phases, each phase being different by 60 degrees.

2. fourth to seventh windings each having three winding portions for forming three phases; one winding portion of each of the fourth and fifth windings is branched and connected to an end of each winding portion of the second winding, and one winding portion of each of the sixth and seventh windings is branched and connected to an end of each winding portion of the third winding, a first winding portion of the fourth winding is wound around the iron core so as to be connected at one end to an end of the S-phase winding portion of the second winding and to be continuous with the R-phase winding portion of the second winding; a second winding portion of the fourth winding is wound around the iron core so as to be continuous with the S-phase winding portion of the second winding, with one end connected to an end of the R-phase winding portion of the second winding, a third winding portion of the fourth winding is wound around the iron core so as to be continuous with the T-phase winding portion of the second winding, with one end connected to an end of the R-phase winding portion of the second winding, a first winding portion of the fifth winding is wound around the iron core so as to be connected at one end to an end of the T-phase winding portion of the second winding and to be continuous with the R-phase winding portion of the second winding; a second winding portion of the fifth winding is wound around the iron core so as to be continuous with the S-phase winding portion of the second winding, with one end connected to an end of the T-phase winding portion of the second winding; a third winding portion of the fifth winding is wound around the iron core so as to be continuous with the T-phase winding portion of the second winding, with one end connected to an end of the S-phase winding portion of the second winding; a first winding portion of the sixth winding is wound around an iron core that is continuous with the U-phase winding portion of the third winding, and has one end connected to an end of the V-phase winding portion of the third winding; a second winding portion of the sixth winding is wound around the iron core so as to be connected at one end to an end of the U-phase winding portion of the third winding and to be continuous with the V-phase winding portion of the third winding, a third winding portion of the sixth winding has one end connected to an end of the U-phase winding portion of the third winding, and is wound around an iron core continuous with the W-phase winding portion of the third winding; a first winding portion of the seventh winding is wound around the iron core so as to be connected at one end to an end of the W-phase winding portion of the third winding and to be continuous with the U-phase winding portion of the third winding; a second winding portion of the seventh winding is wound around the iron core so as to be connected at one end to an end of the W-phase winding portion of the third winding and to be continuous with the V-phase winding portion of the third winding, a third winding portion of the seventh winding is wound around the iron core so as to be connected at one end to an end of the V-phase winding portion of the third winding and to be continuous with the W-phase winding portion of the third winding, The fourth to seventh windings are wound with a number of turns that is 0.36 times that of the second and third windings, 2. The multi-phase transformer according to claim 1, wherein the other ends of the fourth to seventh windings are secondary output terminals, and a total of 12 phase voltages are output, each phase differing by 30 degrees.

3. A power supply comprising: the multi-phase transformer according to claim 1 or 2; and a full-wave rectifier circuit that rectifies an output of the multi-phase transformer, The power conversion device is characterized in that the full-wave rectifier circuit has, in addition to output terminals of a positive terminal and a negative terminal, a neutral terminal connected to the neutral point common to the second winding and the third winding.

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