HK1163930A - Transformer - Google Patents

Description

Transformer device

Technical Field

The present invention relates to transformers, and more particularly to transformers that attempt to reduce height.

Background

Conventionally, rail vehicles such as a new railway line are required to increase the transportation amount as fast as possible. Therefore, it is necessary to reduce the size and weight of the vehicle body and the accessories, but the vehicle-mounted transformer, which has a particularly high mass, has a larger capacity in the accessories.

In recent years, from the viewpoint of no obstacles, the floor of a vehicle is increasingly required to be low, and therefore, not only is downsizing and weight reduction required for an underfloor device such as an onboard transformer mounted under the floor of a vehicle such as an ac electric train, but also a reduction in height is strongly required for lowering the floor of the vehicle.

For example, japanese patent laying-open No. 9-134823 (patent document 1) discloses a core-type on-board transformer as follows. That is, in the internal iron type on-vehicle transformer in which the cooling system is the strong oil air cooling type, the low-voltage winding is wound around the outer periphery of the leg portion of the core, the high-voltage winding is wound around the outer periphery of the low-voltage winding, and the cooling oil passage is formed between the windings, thereby configuring the internal structure. The internal structure is disposed in the case such that the cooling oil passage is parallel to the bottom surface of the case. The core has two leg portions, and each of the low-voltage and high-voltage windings is wound in a divided manner on each of the leg portions. That is, since the winding is divided into two, the capacity of each winding becomes 1/2. Meanwhile, the radial size of one turn of the winding becomes smaller by reducing the size of the winding conductor. Therefore, the height of the entire transformer can be reduced, and the capacity map can be miniaturized.

Patent document 1: japanese patent laid-open No. 9-134823

Here, for example, in the configuration in which the separately wound low-voltage windings are connected to different motors as described above, if one motor fails, the current does not flow through the low-voltage winding and the high-voltage winding corresponding to the failed motor. As described above, magnetic flux is no longer generated in the low-voltage winding and the high-voltage winding, and the reactance of each winding corresponding to the motor in which no failure has occurred may decrease.

However, the vehicle-mounted transformer described in patent document 1 does not disclose a structure for solving such a problem.

Disclosure of Invention

The present invention has been made to solve the above problems, and an object of the present invention is to provide a transformer capable of reducing the height of the transformer and preventing a decrease in reactance.

A transformer according to an aspect of the present invention includes: a first core having a plurality of leg portions arranged at intervals from each other; a plurality of high-voltage side coils wound on the plurality of leg portions, respectively, and receiving a common single-phase alternating current; and a plurality of low-voltage side coils which are provided corresponding to the high-voltage side coils, are magnetically coupled to the corresponding high-voltage side coils, and are wound around the plurality of leg portions, respectively, the high-voltage side coils and the corresponding low-voltage side coils forming a plurality of coil groups, and the transformer further includes a second core provided between the adjacent coil groups.

Preferably, the first core and the second core are provided separately from each other.

Preferably, the first core and the second core are integrated.

Preferably, the core has at least three openings, the plurality of leg portions are respectively provided between the openings, and the low-voltage side coil and the high-voltage side coil in each coil group are wound around the leg portions through the openings on both adjacent sides of the leg portions and are stacked in the extending direction of the leg portions.

Preferably, the low-side coils in each coil group are coupled to different loads.

It is preferable that the minimum value of the length of the second core in the arrangement direction of the leg portions is determined based on the number of turns of the low-voltage side coil in the coil group adjacent to the second core, the current flowing through the low-voltage side coil in the coil group adjacent to the second core, the sizes of the low-voltage side coil and the high-voltage side coil in the coil group adjacent to the second core, and the saturation magnetic flux density of the second core.

Further, a transformer according to another aspect of the present invention includes: a first core having a plurality of legs; a high-voltage side coil; and a low voltage side coil dividing the low voltage side coil and the high voltage side coil into a plurality of coil groups, the low voltage side coil and the high voltage side coil of the plurality of coil groups being wound on the plurality of leg portions, respectively, the high voltage side coil of each coil group receiving a common single-phase alternating current, the low voltage side coil and the high voltage side coil of each coil group being magnetically coupled to each other, the transformer further including a second core disposed between adjacent coil groups.

According to the present invention, the height of the transformer can be reduced and the reactance can be prevented from being lowered.

Drawings

Fig. 1 is a circuit diagram showing a configuration of an ac electric vehicle according to embodiment 1 of the present invention.

Fig. 2 is a perspective view showing the structure of a transformer according to embodiment 1 of the present invention.

Fig. 3 is a diagram showing a cross section III-III of the transformer in fig. 2, and a current and a magnetic flux generated in the transformer.

Fig. 4(a) is a cross-sectional view of a window portion of the transformer showing a current generated in the transformer. Fig. 4(b) is a graph showing leakage magnetic flux generated in the core in the transformer.

Fig. 5 is a circuit diagram showing a configuration of an ac electric vehicle according to embodiment 1 of the present invention.

Fig. 6 is a perspective view showing the structure of a transformer according to embodiment 1 of the present invention.

Fig. 7 is a view showing a section VII-VII of the transformer in fig. 6, and a current and a magnetic flux generated in the transformer.

Fig. 8 is a diagram showing leakage magnetic flux in the transformer according to embodiment 1 of the present invention.

Fig. 9 is a diagram showing main magnetic flux during one-side operation in the transformer according to embodiment 1 of the present invention.

Fig. 10 is a diagram showing leakage magnetic flux when one-side operation is performed assuming that the transformer according to embodiment 1 of the present invention does not include a sub-core.

Fig. 11 is a diagram showing leakage magnetic flux when the transformer according to embodiment 1 of the present invention is operated on one side.

Fig. 12(a) is a cross-sectional view of a window portion of the transformer showing a current generated in the transformer. Fig. 12(b) is a graph showing leakage magnetic flux generated in the core in the transformer.

Fig. 13 is a perspective view showing the structure of a transformer according to embodiment 2 of the present invention.

Fig. 14 is a diagram showing an XIV-XIV cross section of the transformer in fig. 13, and a current and a magnetic flux generated in the transformer.

Fig. 15 is a diagram showing a structure of a transformer according to embodiment 3 of the present invention.

Fig. 16 is a diagram showing a structure of a transformer according to embodiment 4 of the present invention.

Fig. 17 is a circuit diagram showing a configuration of an ac electric vehicle according to embodiment 5 of the present invention.

Fig. 18 is a circuit diagram showing a configuration of an ac electric vehicle according to embodiment 6 of the present invention.

Description of the reference symbols

1. 11, 1A, 1B, 11A, 11B, 41A, 41B high-voltage side coil

2. 12, 2A, 2B, 12A, 12B, 42A, 42B low voltage side coil

5A, 5B, 5C, 5D converter

6A, 6B, 6C, 6D inverter

15. 16, 17 auxiliary iron core

31. 32, 33, 34 legs

50. 51, 53, 54, 55, 56 transformer

60 iron core

61. 62, 63 main iron core

91 overhead line

92 electric conduction bow

100. 101, 105, 106 transformer device

200. 201, 205, 206 AC electric train

MA, MB, MC, MD electric motors

Window parts of W1, W2, W3, W4 and W5

Coil group of G1, G2, G3 and G4

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

< embodiment 1>

First, a configuration in which each coil in the transformer is not divided will be described, and then, a configuration in which each coil in the transformer is divided will be described.

Fig. 1 is a circuit diagram showing a configuration of an ac electric vehicle according to embodiment 1 of the present invention.

Referring to fig. 1, an ac trolley 200 includes a pantograph 92, a transformer 100, and motors MA and MB. The transformer apparatus 100 includes a transformer 50, converters 5A and 5B, and inverters 6A and 6B. The transformer 50 includes high-voltage side coils 1, 11 and low-voltage side coils 2, 12.

The pantograph 92 is connected to the overhead wire 91. The high-voltage side coil 1 has a first terminal connected to the pantograph 92 and a second terminal connected to a ground node supplying a ground voltage. The high-voltage side coil 11 has a first terminal connected to the pantograph 92 and a second terminal connected to a ground node that supplies a ground voltage.

The low-voltage side coil 2 is magnetically coupled to the high-voltage side coil 1, and has a first end connected to a first input terminal of the converter 5A and a second end connected to a second input terminal of the converter 5A. The low-voltage side coil 12 is magnetically coupled to the high-voltage side coil 11, and has a first end connected to the first input terminal of the converter 5B and a second end connected to the second input terminal of the converter 5B.

The single-phase ac voltage supplied from the overhead wire 91 is supplied to the high-voltage side coils 1 and 11 via the pantograph 92.

An alternating voltage is induced in the low-voltage side coils 2 and 12 by the alternating voltage supplied to the high-voltage side coils 1 and 11, respectively.

The converter 5A converts an alternating-current voltage induced in the low-voltage side coil 2 into a direct-current voltage. The converter 5B converts an alternating-current voltage induced in the low-voltage side coil 12 into a direct-current voltage.

The inverter 6A converts the direct-current voltage received from the converter 5A into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MA. The inverter 6B converts the direct-current voltage received from the converter 5B into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MB.

The motor MA is driven based on the three-phase alternating-current voltage received from the inverter 6A. The motor MB is driven based on the three-phase alternating-current voltage received from the inverter 6B.

Fig. 2 is a perspective view showing the structure of a transformer according to embodiment 1 of the present invention.

Referring to fig. 2, the transformer 50 is, for example, a Shell-Type (Shell-Type) transformer. The transformer 50 also includes a core 60. The core 60 has first and second side surfaces facing each other, and window portions W1 and W2 penetrating from the first side surface to the second side surface.

The high-voltage side coils 1 and 11 and the low-voltage side coils 2 and 12 are wound to pass through the window portions W1 and W2.

Each of the high-voltage side coils 1 and 11 and the low-voltage side coils 2 and 12 includes, for example, a plurality of laminated disc windings in a disc shape. The disc windings of adjacent layers are electrically connected. Each of the disc windings of the high-voltage side coils 1 and 11 and the low-voltage side coils 2 and 12 is formed by a rectangular conductive wire wound in a substantially elliptical shape.

The high-voltage side coil 1 is disposed between the low-voltage side coil 2 and the low-voltage side coil 12 at a position facing the low-voltage side coil 2, and is magnetically coupled to the low-voltage side coil 2.

The high-voltage side coil 11 is connected in parallel with the high-voltage side coil 1, is provided between the low-voltage side coil 2 and the low-voltage side coil 12 at a position facing the low-voltage side coil 12, and is magnetically coupled to the low-voltage side coil 12.

Fig. 3 is a diagram showing a cross section III-III of the transformer in fig. 2, and a current and a magnetic flux generated in the transformer.

First, an ac voltage is supplied from the overhead wire 91 to the pantograph 92. An alternating voltage supplied from an overhead wire 91 is applied to the high-voltage side coils 1 and 11 via the pantograph 92. In this way, alternating currents IH flow through the high-voltage side coils 1 and 11, respectively.

By the alternating current IH, a main magnetic flux FH is generated in the core 60. In this way, the main magnetic flux FH generates an alternating current IL and an alternating voltage in the low-voltage side coil 2 according to the ratio of the number of turns of the low-voltage side coil 2 to the number of turns of the high-voltage side coil 1. Further, the main magnetic flux FH causes an alternating current IL and an alternating voltage to be generated in the low-voltage side coil 12 in accordance with the ratio of the number of turns of the low-voltage side coil 12 to the number of turns of the high-voltage side coil 11.

Here, since the number of turns of the low-voltage side coils 2 and 12 is smaller than the number of turns of the high-voltage side coils 1 and 11, an ac voltage obtained by stepping down the ac voltage applied to the high-voltage side coils 1 and 11 is induced in the low-voltage side coils 2 and 12, respectively.

The ac voltage induced in the low-voltage side coil 2 is supplied to the converter 5A. Further, the alternating-current voltage induced in the low-voltage side coil 12 is supplied to the converter 5B.

Fig. 4(a) is a cross-sectional view of a window portion of the transformer showing a current generated in the transformer. Fig. 4(b) is a graph showing leakage magnetic flux generated in the core in the transformer. In fig. 4(b), the vertical axis represents the magnitude of the leakage magnetic flux F.

The transformer 50 includes different high-side coils 1 and 11. In the transformer 50, the low-voltage side coils 2 and 12 are disposed on both sides of the high-voltage side coils 1 and 11. With this structure, the low-voltage side coils 2 and 12 can be magnetically weakly coupled.

That is, as shown in fig. 4(b), since the leakage magnetic fluxes generated in the low-voltage side coils 2 and 12 do not overlap each other, the magnetic interference of the low-voltage side coils 2 and 12 can be reduced, and the output of the transformer 50 can be stabilized.

However, in the transformer 50, as the power capacity and the number of turns of the coil increase, the number of stacked disc windings increases, and therefore the height of the transformer, that is, the size of the transformer in the stacking direction of the disc windings increases. In order to reduce the height of the transformer, it is conceivable to make the conductive line of the coil thin, but power consumption in the coil increases.

Therefore, in the transformer 51 described below, the above problem is solved by dividing the coil. The structure and operation of the transformer 51 are the same as those of the transformer 50 except for the following description.

Fig. 5 is a circuit diagram showing a configuration of an ac electric vehicle according to embodiment 1 of the present invention.

Referring to fig. 5, ac trolley 201 includes pantograph 92, transformer 101, and motors MA and MB. The transformer device 101 includes a transformer 51, converters 5A and 5B, and inverters 6A and 6B. The transformer 51 includes coil groups G1, G2. The coil group G1 includes high-voltage side coils 1A, 1B and low-voltage side coils 2A, 2B. The coil group G2 includes high-voltage side coils 11A, 11B and low-voltage side coils 12A, 12B.

In the transformer 51, each coil in the transformer 50 is divided into coil groups G1 and G2. That is, the high-voltage side coils 1A and 1B are obtained by dividing the high-voltage side coil 1, the low-voltage side coils 2A and 2B are obtained by dividing the low-voltage side coil 2, the high-voltage side coils 11A and 11B are obtained by dividing the high-voltage side coil 11, and the low-voltage side coils 12A and 12B are obtained by dividing the low-voltage side coil 12.

The pantograph 92 is connected to the overhead wire 91. The high-voltage side coil 1A has a first end connected to the pantograph 92 and a second end. The high-voltage side coil 1B has a first end connected to the second end of the high-voltage side coil 1A, and a second end connected to a ground node to which a ground voltage is supplied. The high-voltage side coil 11A has a first end connected to the pantograph 92, and a second end. The high-voltage side coil 11B has a first end connected to the second end of the high-voltage side coil 11A, and a second end connected to a ground node that supplies a ground voltage.

The low-voltage side coil is arranged corresponding to the high-voltage side coil and is magnetically coupled with the corresponding high-voltage side coil. That is, the low-voltage side coil 2A is magnetically coupled to the high-voltage side coil 1A, and has a first end connected to the first input terminal of the converter 5A and a second end. The low-voltage side coil 2B is magnetically coupled to the high-voltage side coil 1B, and has a first end connected to the second end of the low-voltage side coil 2A and a second end connected to the second input terminal of the converter 5A. Low-voltage side coil 12A is magnetically coupled to high-voltage side coil 11A, and has a first end connected to the first input terminal of converter 5B, and a second end. The low-voltage side coil 12B is magnetically coupled to the high-voltage side coil 11B, and has a first end connected to the second end of the low-voltage side coil 12A and a second end connected to the second input terminal of the converter 5B.

The single-phase ac voltage supplied from the overhead wire 91 is supplied to the high-voltage side coils 1A, 1B, 11A, and 11B via the pantograph 92.

By the alternating voltage supplied to the high-voltage side coils 1A and 11A, alternating voltages are induced in the low-voltage side coils 2A and 12A, respectively. An ac voltage is induced in the low-voltage side coils 2B and 12B by the ac voltage supplied to the high-voltage side coils 1B and 11B, respectively.

The converter 5A converts an alternating-current voltage induced in the low-voltage side coils 2A and 2B into a direct-current voltage. The converter 5B converts the alternating-current voltage induced in the low-voltage side coils 12A and 12B into a direct-current voltage.

The inverter 6A converts the direct-current voltage received from the converter 5A into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MA. The inverter 6B converts the direct-current voltage received from the converter 5B into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MB.

The motor MA is driven based on the three-phase alternating-current voltage received from the inverter 6A. The motor MB is driven based on the three-phase alternating-current voltage received from the inverter 6B.

Fig. 6 is a perspective view showing the structure of a transformer according to embodiment 1 of the present invention.

Referring to fig. 6, the transformer 51 is, for example, a Shell-Type transformer. The transformer 51 further includes a main core 61 and a sub core 15. The main core 61 has first and second side surfaces facing each other, and window portions W1 to W3 penetrating from the first side surface to the second side surface. The main core 61 has leg portions 31 and 32 arranged at intervals. The leg 31 is disposed between the window portions W1 and W2. The leg 32 is disposed between the window portions W2 and W3.

Each of the high-voltage side coils 1A, 1B, 11A, and 11B and the low-voltage side coils 2A, 2B, 12A, and 12B includes, for example, a plurality of laminated disc-shaped disc windings. The disc windings of adjacent layers are electrically connected. Each of the disc windings of the high-voltage side coils 1A, 1B, 11A, and 11B and the low-voltage side coils 2A, 2B, 12A, and 12B is formed by a rectangular conductive wire wound in a substantially elliptical shape.

The high-voltage side coil 1A is provided between the low-voltage side coil 2A and the low-voltage side coil 2B at a position opposite to the low-voltage side coil 2A, and is magnetically coupled to the low-voltage side coil 2A.

The high-voltage side coil 1B is connected in parallel with the high-voltage side coil 1A, is provided between the low-voltage side coil 2A and the low-voltage side coil 2B at a position facing the low-voltage side coil 2B, and is magnetically coupled to the low-voltage side coil 2B.

The high-voltage side coil 11A is provided between the low-voltage side coil 12A and the low-voltage side coil 12B at a position opposite to the low-voltage side coil 12A, and is magnetically coupled to the low-voltage side coil 12A.

The high-voltage side coil 11B is connected in parallel with the high-voltage side coil 11A, is provided between the low-voltage side coil 12A and the low-voltage side coil 12B at a position facing the low-voltage side coil 12B, and is magnetically coupled to the low-voltage side coil 12B.

The high-voltage side coil and the low-voltage side coil in each coil group are wound around the leg portion through the windows on the adjacent two sides of the leg portion, and are laminated in the extending direction of the leg portion. That is, the high-voltage side coils 1A and 1B and the low-voltage side coils 2A and 2B are wound to penetrate the leg 31 between the windows W1 and W2 through the windows W1 and W2, and are stacked in the penetrating direction of the leg 31. The high-voltage side coils 11A and 11B and the low-voltage side coils 12A and 12B are wound to penetrate the leg 32 between the windows W2 and W3 through the windows W2 and W3, and are stacked in the penetrating direction of the leg 32.

The sub-core 15 is disposed between the coil groups G1 and G2. The main core 61 and the sub core 15 are provided separately from each other.

In this way, the sub core 15 is formed as an independent structure, and a gap is provided between the main core 61 and the sub core 15, whereby the sub core 15 can be easily manufactured. Further, the sub-core 15 can be reduced in weight in the gap portion.

Fig. 7 is a view showing a section VII-VII of the transformer in fig. 6, and a current and a magnetic flux generated in the transformer.

First, a single-phase ac voltage is supplied from the overhead wire 91 to the pantograph 92. An ac voltage supplied from the overhead wire 91 is applied to the high-voltage side coils 1A, 1B, 11A, 11B via the pantograph 92. That is, the high-side coils in each coil group receive a common single-phase alternating current. Thus, the alternating current IH flows through the high-voltage side coils 1A, 1B, 11A, and 11B.

The main magnetic flux FH1 is generated in the main core 61 by the alternating current IH flowing through the high-voltage side coils 1A and 1B. In this way, the main magnetic flux FH1 generates an alternating current IL1 and an alternating voltage in the low-voltage side coil 2A corresponding to the ratio of the number of turns of the low-voltage side coil 2A to the number of turns of the high-voltage side coil 1A. Further, the main magnetic flux FH1 causes an alternating current IL1 and an alternating voltage to be generated in the low-voltage side coil 2B in accordance with the ratio of the number of turns of the low-voltage side coil 2B to the number of turns of the high-voltage side coil 1B.

Here, since the number of turns of the low-voltage side coils 2A and 2B is smaller than the number of turns of the high-voltage side coils 1A and 1B, an ac voltage obtained by stepping down the ac voltage applied to the high-voltage side coils 1A and 1B is induced in the low-voltage side coils 2A and 2B, respectively.

Similarly, a main magnetic flux FH11 is generated by the alternating current IH flowing through the high-voltage side coils 11A and 11B. In this way, the main magnetic flux FH11 generates an alternating current IL11 and an alternating voltage in the low-voltage side coil 12A corresponding to the ratio of the number of turns of the low-voltage side coil 12A to the number of turns of the high-voltage side coil 11A. Further, the main magnetic flux FH11 causes an alternating current IL11 and an alternating voltage to be generated in the low-voltage side coil 12B in accordance with the ratio of the number of turns of the low-voltage side coil 12B to the number of turns of the high-voltage side coil 11B.

Here, since the number of turns of the low-voltage side coils 12A and 12B is smaller than the number of turns of the high-voltage side coils 11A and 11B, an ac voltage obtained by stepping down the ac voltage applied to the high-voltage side coils 11A and 11B is induced in the low-voltage side coils 12A and 12B, respectively.

The ac voltage induced in the low-voltage side coils 2A and 2B is supplied to the converter 5A. Further, the ac voltage induced in low-voltage side coils 12A and 12B is supplied to converter 5B.

The converter 5A converts the ac voltage supplied from the low-voltage side coils 2A and 2B into a dc voltage, and outputs the dc voltage to the inverter 6A. The converter 5B converts the ac voltage supplied from the low-voltage side coils 12A and 12B into a dc voltage, and outputs the dc voltage to the inverter 6B.

The inverter 6A converts the direct-current voltage received from the converter 5A into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MA. Further, inverter 6B converts the direct-current voltage received from converter 5B into a three-phase alternating-current voltage, and outputs it to motor MB.

The motor MA is rotated based on the three-phase ac voltage received from the inverter 6A. Further, motor MB is rotated based on the three-phase ac voltage received from inverter 6B.

In this way, in the transformer 51, the low-voltage side coil and the high-voltage side coil are divided into a plurality of coil groups, and the leg portion is provided for each coil group. The low-voltage side coil and the high-voltage side coil of the plurality of coil groups are wound around the plurality of leg portions, respectively. With this structure, the height of the transformer, that is, the length of the transformer in the extending direction of the leg portion can be reduced. Further, it is not necessary to increase the sectional area of the conductor line of the coil, and power consumption in the coil can be prevented from increasing.

That is, in the transformer 51, the low-voltage side coils 2 and 12 and the high-voltage side coils 1 and 11 in the transformer 50 are divided into two coil groups, and therefore the power capacity of each coil group becomes 1/2. Here, since the supply voltage is fixed and the power capacity is equal to the voltage × the current, when the power capacity of each coil group becomes 1/2, the current flowing through each coil becomes 1/2. Thus, the number of disc windings stacked in each coil can be reduced, and therefore, the height of the transformer can be reduced. Alternatively, instead of reducing the number of disc windings, the height of each coil group is reduced by reducing the cross-sectional area of the conductor lines of the high-voltage side coils 1A, 1B, 11A, 11B and the low-voltage side coils 2A, 2B, 12A, 12B, and the height of the entire transformer can be reduced.

Next, the problem of reactance drop in the transformer and a solution thereof will be described. Fig. 8 is a diagram showing leakage magnetic flux in the transformer according to embodiment 1 of the present invention.

Referring to fig. 8, in the transformer 51, in addition to main fluxes FH1 and FH11 generated by the ac current IH flowing through the high-voltage side coil, leakage fluxes FKH1 and FKH11 that do not flow through the main core 61 are generated. In addition, leakage fluxes FKL1 and FKL11 that do not flow through the main core 61 are generated by the alternating currents IL1 and IL11 flowing through the low-voltage side coil.

Fig. 9 is a diagram showing main magnetic flux during one-side operation in the transformer according to embodiment 1 of the present invention.

In transformer 51, for example, even when motor MB has failed, motor MA can be operated alone by coil group G1. In such a one-side operation, the main magnetic flux FH11 is not generated because the high-voltage side coils 11A and 11B and the low-voltage side coils 12A and 12B do not function, that is, the current does not flow through the high-voltage side coils 11A and 11B and the low-voltage side coils 12A and 12B.

Fig. 10 is a diagram showing leakage magnetic flux when one-side operation is performed assuming that the transformer according to embodiment 1 of the present invention does not include a sub-core.

Referring to fig. 10, for example, if a failure occurs in motor MB and current no longer flows through high-voltage side coils 11A and 11B and low-voltage side coils 12A and 12B, leakage flux FKH11 and FKL11 are no longer generated.

Here, since the transformer shown in fig. 10 does not include the sub-core 15, the leakage flux FKH1 and FKL1 spread in the window W2, and the magnetic path length becomes long. Therefore, compared to the state shown in fig. 8, the magnetomotive force at window W2 becomes 1/2, that is, the magnitude of leakage magnetic flux at window W2 becomes 1/2, and therefore the reactance of low-voltage side coils 2A and 2B and high-voltage side coils 1A and 1B decreases.

Here, the strength of the magnetic field is inversely proportional to the magnetic path length according to ampere's law. The weakening of the magnetic field means that the magnetic flux density becomes small and the self-inductance of the coil becomes small. Further, the reactance is greatly affected by leakage inductance due to a leakage magnetic field. Therefore, the magnetic path length becomes long, so that the magnetic field becomes weak, and the self-inductance of the coil is reduced. As such, leakage inductance decreases, and thus reactance decreases.

In the normal operation shown in fig. 8, the leakage fluxes FKH1 and FKH11 are combined, and the leakage fluxes FKL1 and FKL11 are combined, so that the magnetomotive force in the window portion W2 is twice as large as that in the state shown in fig. 10. Therefore, even if the magnetic path lengths of the leakage fluxes FKH1 and FKH11 and the leakage fluxes FKL1 and FKL11 are the same as those in the state shown in fig. 10, the reactances of the high-voltage side coils 1A, 1B, 11A, 11B and the low-voltage side coils 2A, 2B, 12A, 12B do not decrease.

Fig. 11 is a diagram showing leakage magnetic flux when the transformer according to embodiment 1 of the present invention is operated on one side.

Referring to fig. 11, for example, if a failure occurs in motor MB and current no longer flows through high-voltage side coils 11A and 11B and low-voltage side coils 12A and 12B, leakage flux FKH11 and FKL11 are no longer generated.

Therefore, the magnetomotive force in the window W2 becomes 1/2 in the state shown in fig. 8. However, in the transformer 51, the leakage flux FKH1 and FKL1 flow through the sub-core 15. Accordingly, since the leakage magnetic flux FKH1 and FKL1 do not spread in the window W2, the magnetic path length of the leakage magnetic flux FKH1 and FKL1 can be 1/2 in the state shown in fig. 10. Therefore, the reactances of the low-voltage side coils 2A and 2B and the high-voltage side coils 1A and 1B are the same as those in the state shown in fig. 8. Therefore, in the transformer 51, even when the single-side operation is performed, the reactance of the low-voltage side coils 2A and 2B and the high-voltage side coils 1A and 1B can be prevented from decreasing, and a stable reactance can be obtained.

Here, in a three-phase transformer, for example, an iron core (inter-phase iron core) is provided between coils of respective phases in order to pass main magnetic flux. In contrast, the transformer according to embodiment 1 of the present invention is a single-phase transformer. In a single-phase transformer, an interphase core as in a three-phase transformer is generally not required. However, in the transformer according to embodiment 1 of the present invention, by providing the sub-core in addition to the main core, for example, when one motor fails and only the other motor is operated, the length of the magnetic path is prevented from being increased, and the reactance is prevented from being decreased.

Next, a method of calculating the width of the sub core in the transformer according to embodiment 1 of the present invention will be described.

If the width of the sub-core 15 is too small, magnetic saturation occurs, and the sub-core no longer functions as a core. On the other hand, if the width of the sub-core 15 is too large, the transformer becomes large. Therefore, the width of the sub-core 15 is preferably set to a minimum value at which saturation does not occur in the leakage magnetic flux.

In the transformer according to embodiment 1 of the present invention, the width of the sub core 15, that is, the minimum value of the length of the sub core 15 in the leg portion arrangement direction is determined based on the number of turns of the low-voltage side coil in the coil group adjacent to the sub core 15, the current flowing through the low-voltage side coil in the coil group adjacent to the sub core 15, the sizes of the low-voltage side coil and the high-voltage side coil in the coil group adjacent to the sub core 15, and the saturation magnetic flux density of the sub core 15.

Fig. 12(a) is a cross-sectional view of a window portion of the transformer showing a current generated in the transformer. Fig. 12(b) is a graph showing leakage magnetic flux generated in the core in the transformer. In fig. 12(b), the vertical axis represents the leakage magnetic flux density FK.

Referring to fig. 12(a) and 12(b), the width of the sub core is calculated as follows.

First, assuming that the number M of turns of the low-voltage side coils 2A, 12A is 150, the current I flowing through the low-voltage side coils 2A, 12A is 500A (amperes), the width W of the window portion W1 is 0.3M, the height HL of the low-voltage side coils 2A, 12A is 50mm, the distance between the low-voltage side coil 2A and the high-voltage side coil 1A and the distance D between the low-voltage side coil 12A and the high-voltage side coil 11A are 15mm, and the height HH of the high-voltage side coils 1A, 11A is 100 mm.

In addition, the number of turns of the coil has an inverse relationship with the current flowing through the coil. When the number of turns of the low-voltage side coil and the current are the above-described values, for example, the number of turns M of the high-voltage side coils 1A and 11A is 500, and the current I flowing through the high-voltage side coils 1A and 11A is 150A (amperes). Therefore, if the number of turns of the low-voltage side coil and the current value are used in the following formula (1), the magnetic flux density of the high-voltage side coils 1A and 11A can be obtained.

When the magnetic permeability of the vacuum is μ, the leakage magnetic flux density BDL when the motor is operated on one side, that is, when only one of the motors MA and MB is operated is expressed by the following formula (1).

μ＝4×π×10^-7，

If the above numerical values are substituted for the formula (1), the

The magnetic flux BS entering the sub-core is a magnetic flux generated by the low-voltage side coil 2A and the high-voltage side coil 1A, and corresponds to the area of the trapezoid on the left side of the graph of fig. 12 (b). The strongest magnetic flux entering the sub core is a portion where the magnetic fluxes generated by the low-voltage side coil 2A and the high-voltage side coil 1A are combined in the sub core. The magnetic flux BS entering the sub-core is expressed by the following equation.

BS＝0.444×(15+(50+15+100))/2＝39.96(T·mm)。

When the saturation magnetic flux density of the sub-core (the magnetic flux density of the magnetic body at this time when the magnetization hardly increases when the external magnetic field is applied to the magnetic body) is BSD, the minimum value WS of the width of the sub-core is expressed by the following equation.

WS＝BS/BSD

Here, when BSD is 1.5(T), the width WS of the sub-core becomes equal to

WS＝39.96/1.5＝26.64(mm)。

That is, by setting the width of the sub core to a value as small as possible of 26.64(mm) or more, it is possible to prevent the reactance of the coil from being decreased when the transformer is operated on one side, and to reduce the size of the transformer.

The saturation magnetic flux density is a value determined by the material of the sub core. As the BSD of the above expression, for example, a small value having a certain margin for the saturation magnetic flux density is set.

As described above, the transformer according to the embodiment of the present invention includes: a main core 61, the main core 61 having a plurality of leg portions arranged at intervals from each other; high-voltage side coils 1A, 1B, 11A, 11B, the high-voltage side coils 1A, 1B, 11A, 11B being wound around the plurality of leg portions, respectively, and receiving a common single-phase alternating current; and a plurality of low-voltage side coils 2A, 12A, 2B, 12B, the plurality of low-voltage side coils 2A, 12A, 2B, 12B being provided corresponding to the high-voltage side coils, magnetically coupled to the corresponding high-voltage side coils, and wound around the plurality of leg portions, respectively, wherein the high-voltage side coils and the corresponding low-voltage side coils form coil groups G1, G2. Further, a sub core 15 is provided between the adjacent coil groups. With this configuration, the height of the transformer can be reduced, and the decrease in reactance due to the increase in the magnetic path length of the leakage flux can be prevented.

Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

< embodiment 2>

The present embodiment relates to a transformer in which the structure of a sub-core is modified as compared with the transformer according to embodiment 1. Except for the following description, the same is applied to the transformer according to embodiment 1.

Fig. 13 is a perspective view showing the structure of a transformer according to embodiment 2 of the present invention. Fig. 14 is a diagram showing an XIV-XIV cross section of the transformer in fig. 13, and a current and a magnetic flux generated in the transformer.

Referring to fig. 13 and 14, in comparison with the transformer according to embodiment 1 of the present invention, the transformer 52 includes the sub-core 14 instead of the sub-core 15. The sub core 14 is provided between the coil groups G1 and G2, and has both ends connected to the main core 61. That is, the sub-core 14 is integrated with the main core 61.

In this way, the gap between the main core and the sub core is eliminated by integrating the main core and the sub core. This can further prevent the magnetic path length of the leakage flux from becoming long during one-side operation, and can further prevent the reactance from decreasing.

The sub core 14 has two end portions connected to the main core 61, but is not limited to this, and may have a structure in which one end of the sub core is connected to the main core and the other end is open.

Since other configurations and operations are the same as those of the transformer according to embodiment 1, detailed description thereof will not be repeated here.

Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

< embodiment 3>

The present embodiment relates to a transformer in which the number of divided coils is increased as compared with the transformer according to embodiment 1. Except for the following description, the same is applied to the transformer according to embodiment 1.

Fig. 15 is a diagram showing a structure of a transformer according to embodiment 3 of the present invention.

Referring to fig. 15, the transformer 53 includes coil groups G1, G2, G3. The coil group G1 includes high-voltage side coils 1A, 1B and low-voltage side coils 2A, 2B. The coil group G2 includes high-voltage side coils 11A, 11B and low-voltage side coils 12A, 12B. The coil group G3 includes high-voltage side coils 41A, 41B and low-voltage side coils 42A, 42B.

The transformer 53 is, for example, a Shell-Type transformer. The transformer 53 also includes a main core 62 and sub-cores 15, 16. The main core 62 has first and second side surfaces facing each other, and window portions W1 to W4 penetrating from the first side surface to the second side surface. The main core 62 has leg portions 31, 32, and 33. The leg 31 is disposed between the window portions W1 and W2. The leg 32 is disposed between the window portions W2 and W3. The leg 33 is disposed between the window portions W3 and W4.

Each of the high-voltage side coils 41A and 41B and the low-voltage side coils 42A and 42B includes, for example, a plurality of laminated disc windings in a disc shape. The disc windings of adjacent layers are electrically connected. Each of the disc windings of the high-voltage side coils 41A and 41B and the low-voltage side coils 42A and 42B is formed by a rectangular conductive wire wound in a substantially elliptical shape.

The high-voltage side coil 41A is provided between the low-voltage side coil 42A and the low-voltage side coil 42B at a position opposite to the low-voltage side coil 42A, and is magnetically coupled to the low-voltage side coil 42A.

The high-voltage side coil 41B is connected in parallel with the high-voltage side coil 41A, is provided between the low-voltage side coil 42A and the low-voltage side coil 42B at a position facing the low-voltage side coil 42B, and is magnetically coupled to the low-voltage side coil 42B.

The high-voltage side coils 41A and 41B and the low-voltage side coils 42A and 42B are wound to penetrate the leg portion 33 between the window portions W3 and W4 through the window portions W3 and W4, and are stacked in the penetrating direction of the leg portion 33.

The sub cores 15 and 16 are disposed between adjacent coil groups. That is, the sub-core 15 is disposed between the coil groups G1 and G2. The sub-core 16 is disposed between the coil groups G2 and G3.

As described above, in the transformer according to embodiment 3 of the present invention, the low-voltage side coil and the high-voltage side coil are divided into three coil groups, and therefore the power capacity of each coil group becomes 1/3. Here, since the power capacity is equal to voltage × current and the supply voltage is fixed, the current flowing through each coil becomes 1/3. As a result, the height of each coil group can be further reduced as compared with the transformer according to embodiment 1 of the present invention, and the height of the entire transformer can be reduced.

Since other configurations and operations are the same as those of the transformer according to embodiment 1, detailed description thereof will not be repeated here.

Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

< embodiment 4>

The present embodiment relates to a transformer in which the number of divided coils is increased as compared with the transformer according to embodiment 3. The transformer is the same as that of embodiment 3 except for the following description.

Fig. 16 is a diagram showing a structure of a transformer according to embodiment 4 of the present invention.

Referring to fig. 16, the transformer 54 includes coil groups G1, G2, G3, G4. The coil group G1 includes high-voltage side coils 1A, 1B and low-voltage side coils 2A, 2B. The coil group G2 includes high-voltage side coils 11A, 11B and low-voltage side coils 12A, 12B. The coil group G3 includes high-voltage side coils 41A, 41B and low-voltage side coils 42A, 42B. The coil group G4 includes high-voltage side coils 43A, 43B and low-voltage side coils 44A, 44B.

The transformer 54 is, for example, a Shell-Type transformer. The transformer 54 also includes a main core 63 and sub-cores 15, 16, 17. The main core 63 has first and second side surfaces facing each other, and window portions W1 to W5 penetrating from the first side surface to the second side surface. The main core 63 has leg portions 31, 32, 33, and 34. The leg 34 is disposed between the window portions W4 and W5.

Each of the high-voltage side coils 43A and 43B and the low-voltage side coils 44A and 44B includes, for example, a plurality of laminated disc windings in a disc shape. The disc windings of adjacent layers are electrically connected. Each of the disc windings of the high-voltage side coils 43A and 43B and the low-voltage side coils 44A and 44B is formed by a rectangular conductive wire wound in a substantially elliptical shape.

The high-voltage side coil 43A is provided between the low-voltage side coil 44A and the low-voltage side coil 44B at a position opposite to the low-voltage side coil 44A, and is magnetically coupled to the low-voltage side coil 44A.

The high-voltage side coil 43B is connected in parallel with the high-voltage side coil 43A, is provided between the low-voltage side coil 44A and the low-voltage side coil 44B at a position facing the low-voltage side coil 44B, and is magnetically coupled to the low-voltage side coil 44B.

The high-voltage side coils 43A and 43B and the low-voltage side coils 44A and 44B are wound to penetrate the leg portion 34 between the window portions W4 and W5 through the window portions W4 and W5, and are stacked in the penetrating direction of the leg portion 34. Further, the sub-core 17 is disposed between the coil groups G3 and G4.

As described above, in the transformer according to embodiment 4 of the present invention, the low-voltage side coil and the high-voltage side coil are divided into four coil groups, and therefore the power capacity of each coil group becomes 1/4. Here, since the power capacity is equal to voltage × current and the supply voltage is fixed, the current flowing through each coil becomes 1/4. As a result, the height of each coil group can be further reduced as compared with the transformer according to embodiment 3 of the present invention, and the height of the entire transformer can be reduced.

Since other configurations and operations are the same as those of the transformer according to embodiment 3, detailed description thereof will not be repeated here.

Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

< embodiment 5>

The present embodiment relates to a transformer in which the configuration of a coil assembly is modified as compared with the transformer according to embodiment 1. Except for the following description, the same is applied to the transformer according to embodiment 1.

Fig. 17 is a circuit diagram showing a configuration of an ac electric vehicle according to embodiment 5 of the present invention.

Referring to fig. 17, ac trolley 205 includes pantograph 92, transformer 105, and motors MA, MB, MC, and MD. The transformer device 105 includes a transformer 55, converters 5A, 5B, 5C, 5D, and inverters 6A, 6B, 6C, 6D. The transformer 55 includes coil groups G1, G2. The coil group G1 includes high-voltage side coils 1A, 1B and low-voltage side coils 2A, 2B. The coil group G2 includes high-voltage side coils 11A, 11B and low-voltage side coils 12A, 12B.

In the transformer device 105, the low-voltage side coils 2A, 2B, 12A, and 12B are coupled to different loads. That is, low-voltage side coil 2A is magnetically coupled to high-voltage side coil 1A, and has a first end connected to the first input terminal of converter 5A and a second end connected to the second input terminal of converter 5A. The low-voltage side coil 2B is magnetically coupled to the high-voltage side coil 1B, and has a first end connected to a first input terminal of the converter 5C and a second end connected to a second input terminal of the converter 5C. Low-voltage side coil 12A is magnetically coupled to high-voltage side coil 11A, and has a first end connected to the first input terminal of converter 5B and a second end connected to the second input terminal of converter 5B. Low-voltage side coil 12B is magnetically coupled to high-voltage side coil 11B, and has a first end connected to a first input terminal of converter 5D and a second end connected to a second input terminal of converter 5D.

The single-phase ac voltage supplied from the overhead wire 91 is supplied to the high-voltage side coils 1A, 1B, 11A, and 11B via the pantograph 92.

By the alternating voltage supplied to the high-voltage side coils 1A and 11A, alternating voltages are induced in the low-voltage side coils 2A and 12A, respectively. An ac voltage is induced in the low-voltage side coils 2B and 12B by the ac voltage supplied to the high-voltage side coils 1B and 11B, respectively.

The converter 5A converts an alternating-current voltage induced in the low-voltage side coil 2A into a direct-current voltage. The converter 5B converts the alternating-current voltage induced in the low-voltage side coil 12A into a direct-current voltage. The converter 5C converts the alternating-current voltage induced in the low-voltage side coil 2B into a direct-current voltage. The converter 5D converts the alternating-current voltage induced in the low-voltage side coil 12B into a direct-current voltage.

The inverter 6A converts the direct-current voltage received from the converter 5A into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MA. The inverter 6B converts the direct-current voltage received from the converter 5B into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MB. The inverter 6C converts the direct-current voltage received from the converter 5C into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MC. The inverter 6D converts the direct-current voltage received from the converter 5D into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MD.

The motor MA is driven based on the three-phase alternating-current voltage received from the inverter 6A. The motor MB is driven based on the three-phase alternating-current voltage received from the inverter 6B. The motor MC is driven based on the three-phase alternating-current voltage received from the inverter 6C. The motor MD is driven based on the three-phase alternating voltage received from the inverter 6D.

Since other configurations and operations are the same as those of the transformer according to embodiment 1, detailed description thereof will not be repeated here.

Therefore, in the transformer according to embodiment 5 of the present invention, similarly to the transformer according to embodiment 1 of the present invention, the height of the transformer can be reduced and the reactance can be prevented from being lowered.

Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and description thereof will not be repeated.

< embodiment 6>

The present embodiment relates to a transformer in which the configuration of a coil assembly is modified as compared with the transformer according to embodiment 1. Except for the following description, the same is applied to the transformer according to embodiment 1.

Fig. 18 is a circuit diagram showing a configuration of an ac electric vehicle according to embodiment 6 of the present invention.

Referring to fig. 18, the ac trolley 206 includes the pantograph 92, the transformer 106, and the motors MA, MB, MC, MD. The transformer device 106 includes a transformer 56, converters 5A, 5B, 5C, 5D, and inverters 6A, 6B, 6C, 6D. Transformer 56 includes coil groups G1, G2. The coil group G1 includes high-voltage side coils 1A, 1B and low-voltage side coils 2A, 2B. The coil group G2 includes high-voltage side coils 11A, 11B and low-voltage side coils 12A, 12B.

In the transformer device 106, the high-voltage side coils 1A, 1B, 11A, and 11B are connected in parallel with each other, and the low-voltage side coils 2A, 2B, 12A, and 12B are coupled to different loads. That is, the high-voltage side coil 1A has a first end connected to the pantograph 92 and a second end connected to a ground node to which a ground voltage is supplied. The high-voltage side coil 1B has a first end connected to the pantograph 92 and a second end connected to a ground node that supplies a ground voltage. The high-voltage side coil 11A has a first end connected to the pantograph 92 and a second end connected to a ground node that supplies a ground voltage. The high-voltage side coil 11B has a first end connected to the pantograph 92 and a second end connected to a ground node that supplies a ground voltage.

The low-voltage side coil 2A is magnetically coupled to the high-voltage side coil 1A, and has a first end connected to a first input terminal of the converter 5A and a second end connected to a second input terminal of the converter 5A. The low-voltage side coil 2B is magnetically coupled to the high-voltage side coil 1B, and has a first end connected to a first input terminal of the converter 5C and a second end connected to a second input terminal of the converter 5C. Low-voltage side coil 12A is magnetically coupled to high-voltage side coil 11A, and has a first end connected to the first input terminal of converter 5B and a second end connected to the second input terminal of converter 5B. Low-voltage side coil 12B is magnetically coupled to high-voltage side coil 11B, and has a first end connected to a first input terminal of converter 5D and a second end connected to a second input terminal of converter 5D.

The single-phase ac voltage supplied from the overhead wire 91 is supplied to the high-voltage side coils 1A, 1B, 11A, and 11B via the pantograph 92.

By the alternating voltage supplied to the high-voltage side coils 1A and 11A, alternating voltages are induced in the low-voltage side coils 2A and 12A, respectively. An ac voltage is induced in the low-voltage side coils 2B and 12B by the ac voltage supplied to the high-voltage side coils 1B and 11B, respectively.

The converter 5A converts an alternating-current voltage induced in the low-voltage side coil 2A into a direct-current voltage. The converter 5B converts the alternating-current voltage induced in the low-voltage side coil 12A into a direct-current voltage. The converter 5C converts the alternating-current voltage induced in the low-voltage side coil 2B into a direct-current voltage. The converter 5D converts the alternating-current voltage induced in the low-voltage side coil 12B into a direct-current voltage.

The inverter 6A converts the direct-current voltage received from the converter 5A into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MA. The inverter 6B converts the direct-current voltage received from the converter 5B into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MB. The inverter 6C converts the direct-current voltage received from the converter 5C into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MC. The inverter 6D converts the direct-current voltage received from the converter 5D into a three-phase alternating-current voltage, and outputs the three-phase alternating-current voltage to the motor MD.

The motor MA is driven based on the three-phase alternating-current voltage received from the inverter 6A. The motor MB is driven based on the three-phase alternating-current voltage received from the inverter 6B. The motor MC is driven based on the three-phase alternating-current voltage received from the inverter 6C. The motor MD is driven based on the three-phase alternating voltage received from the inverter 6D.

Since other configurations and operations are the same as those of the transformer according to embodiment 1, detailed description thereof will not be repeated here.

Therefore, in the transformer according to embodiment 6 of the present invention, similarly to the transformer according to embodiment 1 of the present invention, the height of the transformer can be reduced and the reactance can be prevented from being lowered.

The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the scope of the claims rather than the description above, and all modifications within the meaning and range equivalent to the scope of the claims are intended to be included.

Claims (7)

1. A transformer, comprising:

a first core (61), the first core (61) having a plurality of legs (31, 32) arranged at intervals;

a plurality of high-voltage side coils (1A, 1B, 11A, 11B), the plurality of high-voltage side coils (1A, 1B, 11A, 11B) being wound around the plurality of legs (31, 32), respectively, and receiving a common single-phase alternating current; and

a plurality of low-voltage side coils (2A, 2B, 12A, 12B), the plurality of low-voltage side coils (2A, 2B, 12A, 12B) being provided corresponding to the high-voltage side coils (1A, 1B, 11A, 11B), being magnetically coupled to the corresponding high-voltage side coils (1A, 1B, 11A, 11B), and being wound around the plurality of legs (31, 32), respectively,

a plurality of coil groups (G1, G2) are formed by the high-voltage side coils (1A, 1B, 11A, 11B) and the corresponding low-voltage side coils (2A, 2B, 12A, 12B),

the transformer further includes a second core (15) disposed between the adjacent coil groups (G1, G2).

2. The transformer of claim 1,

the first core (61) and the second core (15) are provided separately from each other.

3. The transformer of claim 1,

the first core (61) and the second core (15) are integrated.

4. The transformer of claim 1,

the core has at least three opening portions (W1, W2, W3),

the plurality of leg portions (31, 32) are respectively provided between the opening portions (W1, W2, W3),

the low-voltage side coils (2A, 2B, 12A, 12B) and the high-voltage side coils (1A, 1B, 11A, 11B) in the coil groups (G1, G2) are wound around the legs (31, 32) through the openings (W1, W2, W3) on both adjacent sides of the legs (31, 32), and are stacked in the extending direction of the legs (31, 32).

5. The transformer of claim 1,

the low-side coils (2A, 2B, 12A, 12B) in each coil group (G1, G2) are coupled to different loads.

6. The transformer of claim 1,

determining a minimum value of a length of the second core (15) in an arrangement direction of the legs (31, 32) based on the number of turns of the low-voltage side coil (2A, 2B, 12A, 12B) in the coil group (G1, G2) adjacent to the second core (15), a current flowing through the low-voltage side coil (2A, 2B, 12A, 12B) in the coil group (G1, G2) adjacent to the second core (15), sizes of the low-voltage side coil (2A, 2B, 12A, 12B) and the high-voltage side coil (1A, 1B, 11A, 11B) in the coil group (G1, G2) adjacent to the second core (15), and a saturation magnetic flux density of the second core (15).

7. A transformer, comprising:

a first core (61), the first core (61) having a plurality of leg portions (31, 32);

high-voltage side coils (1A, 1B, 11A, 11B); and

low-voltage side coils (2A, 2B, 12A, 12B),

dividing the low-voltage side coils (2A, 2B, 12A, 12B) and the high-voltage side coils (1A, 1B, 11A, 11B) into a plurality of coil groups (G1, G2),

the low-voltage side coils (2A, 2B, 12A, 12B) and the high-voltage side coils (1A, 1B, 11A, 11B) in the plurality of coil groups (G1, G2) are wound around the plurality of legs (31, 32), respectively,

the high-voltage side coils (1A, 1B, 11A, 11B) in each of the coil groups (G1, G2) receive a common single-phase alternating current,

the low-voltage side coils (2A, 2B, 12A, 12B) and the high-voltage side coils (1A, 1B, 11A, 11B) in each of the coil groups (G1, G2) are magnetically coupled to each other,

the transformer further includes a second core (15) disposed between the adjacent coil groups (G1, G2).