Variable Flux Voltage-Regulating and Rectifying Transformer for Electric Traction

Abstract

The present invention belongs to the technical field of transformers, and particularly relates to a variable-flux voltage-regulating rectifier transformer for electric vehicles. It includes: a three-phase coil with a double-split four-coil structure, the three-phase coil is divided into a valve-side coil and a network-side coil corresponding to the valve-side coil. The valve-side coil is split into two parts, namely three star-connected first valve-side coils and three delta-connected second valve-side coils. The network-side coil is split into three delta-connected first network-side coils and three delta-connected second network-side coils. In each phase coil, the first network-side coil and the second network-side coil are connected in parallel; the first network-side coil or the second network-side coil is provided with a first gear corresponding to the first voltage of the network-valve and a second gear corresponding to the second voltage of the network-valve. The gear adjustment of the present invention is convenient and flexible. It can not only conveniently realize the interchange of the valve-side output voltage, but also meet the gear adjustment requirements of the primary-side network voltage tapping range, which is convenient for maintenance and management. There is no structural change, and the position of the external connection line of the network-side coil remains unchanged, which is convenient for on-site operation, maintenance and management.

Description

Technical Field

[0001] The present invention belongs to the technical field of transformers, and particularly relates to a variable-flux voltage-regulating and rectifying transformer for electric vehicles. Background Art

[0002] Environment and climate have become important topics of concern in the world today. Traveling by tram (trolleybus) can generally be regarded as green transportation with zero pollutant emissions. Currently, there are two DC traction power supply systems at the traction rectifier stations of trams (trolleybuses), namely the DC 600V system and the DC 750V system. Due to the limitation of voltage levels, the two systems cannot be used interchangeably, the overall utilization rate is relatively low, and the types of locomotives selected are also limited. If a traction system that can be used interchangeably between DC 600V and DC 750V can be realized to achieve the mutual switching between the two systems, it would be the most ideal solution.

[0003] Since the rectifiers used in trams (trolleybuses) are uncontrollable power diodes, in the prior art, the output voltage on the valve side of the rectifier transformer is adjusted to change the voltage level of the DC output system. The following main problems exist in this technical solution:

[0004] Firstly, the traction rectifier station of a tram (trolleybus) generally has an axial double-split four-coil structure. The 12-pulse rectification is formed by the parallel connection of multiple three-phase bridge rectifier circuits connected to two valve-side coils. The grid side is a 10kV system. The AC output voltage on the valve side corresponding to the 600V DC system is 485V, and the AC output voltage on the valve side corresponding to the 750V DC system is 590V. One of the two windings on the valve side is connected in △ and the other is connected in Y, and the number of turns differs by times. To ensure the balance of voltage output, the difference in no-load line voltages between the two windings on the valve side should be less than 0.3%. Therefore, the available turn ratio on the valve side of the rectifier transformer is very limited. If the voltage outputs of 485V and 590V are achieved by changing the number of turns on the valve side, it is very difficult to ensure that the voltages of the two gears both meet the requirement that the difference in no-load line voltages on the valve side < 0.3%. In addition, the deviation requirement of the turns ratio between the grid side and the valve side of the transformer is less than ±0.5%, which further narrows the selection range of the number of turns of the Y-connected and △-connected windings on the valve side. In summary, by changing the number of turns on the valve side, it is very difficult to obtain an accurately matched result and it is also very difficult to meet the national standard.

[0005] Secondly, the traction substations of general trams (trolleybuses) are mostly built in bustling urban areas with a dense population and limited construction space. Therefore, the space of the traction distribution room is also very limited. Even if the accurately matched number of turns of the coil is calculated, each time the gear is changed, the Y-connected and △-connected copper bars on the valve side need to be replaced. This is not only difficult to operate, but also requires space for storing spare copper bars. Moreover, due to structural limitations, the 485V and 590V △-connected copper bars cannot be used interchangeably.

[0006] Thirdly, the valve side of the rectifier transformer is generally wound with copper foil and led out by copper busbars. Secondary voltage regulation on the valve side will add copper foil and lead-out copper busbars on the valve side. Due to the occupied position of the copper busbars, it brings difficulties to the accuracy of transformer impedance calculation, and it is very difficult to ensure the spatial position symmetry between the low-voltage coil and the high-voltage coil. Summary of the Invention

[0007] The present invention provides a variable-flux voltage-regulating rectifier transformer for electric vehicles to solve the problem that the current two DC traction power supply systems cannot be universal.

[0008] To solve the above technical problems, the technical solution of the present invention is: the variable-flux voltage-regulating rectifier transformer for electric vehicles includes a three-phase coil with a double-split four-coil structure. The three-phase coil is divided into a valve-side coil and a network-side coil corresponding to the valve-side coil. The valve-side coil is split into two parts: three star-connected first valve-side coils and three delta-connected second valve-side coils. The network-side coil is split into three delta-connected first network-side coils and three delta-connected second network-side coils. In each phase coil, the first network-side coil and the second network-side coil are connected in parallel;

[0009] The first network-side coil or the second network-side coil is provided with a first gear corresponding to the first voltage between the network and the valve and a second gear corresponding to the second voltage between the network and the valve. The first voltage is higher than the second voltage. By changing the gear of the network-side coil, different turn electromotive forces of the network-side coil are obtained.

[0010] According to the transformer characteristics, the turn electromotive force of the network-side coil is equal to that of the valve-side coil. Since the turn electromotive force of the valve side changes, the output voltage of the valve side is changed, thus achieving the purpose of realizing the transformation of the secondary output voltage of the transformer. During the process of changing the two turn electromotive forces, the magnetic flux density of the transformer also changes accordingly, and under the two voltage regulation methods, the magnetic flux density cannot be saturated. The change of the valve-side voltage is realized through the electromagnetic induction change formed by the network-side coil and the iron core. On the basis of realizing the variable-flux voltage regulation method on the network side, the number of turns of the two parallel coils is set separately to avoid the occurrence of circulating current between the upper and lower coils due to different numbers of turns.

[0011] Optionally, the gear is adjusted through a voltage regulation panel. The voltage regulation panel includes a wiring board, an incoming line terminal led out from the network-side coil and arranged on the wiring board, a first voltage outgoing line terminal, a second voltage outgoing line terminal, and a tap-changing board connecting the terminals; when the tap-changing board connects the first voltage outgoing line terminal and the second voltage outgoing line terminal, the voltage regulation coil between the first voltage outgoing line terminal and the second voltage outgoing line terminal is short-circuited, and the power is taken out from the first voltage outgoing line terminal, which is the first gear; when the connection between the first voltage outgoing line terminal and the second voltage outgoing line terminal is disconnected, the voltage regulation coil between the first voltage outgoing line terminal and the second voltage outgoing line terminal is connected, and the power is taken out from the second voltage outgoing line terminal as the second gear.

[0012] Optionally, the voltage regulating panel further includes a plurality of first tapping terminals for regulating the voltage of the first gear and a plurality of second tapping terminals for regulating the voltage of the second gear. The first tapping terminals are led out from the first tapping gear coil between the incoming line terminal and the first voltage outgoing line terminal, and the second tapping terminals are led out from the second tapping gear coil in the voltage regulating coil.

[0013] Optionally, short-circuit the voltage regulating coil and disconnect the second tapping terminals, and then connect the corresponding first tapping terminals through the tapping board to regulate the voltage of the first gear; connect the voltage regulating coil and adjust the first tapping gear to the maximum, and then connect the corresponding second tapping terminals through the tapping board to regulate the voltage of the second gear.

[0014] Optionally, the voltage regulation range of the first tapping terminal or the second tapping terminal is ±5% or ±2×2.5%.

[0015] Optionally, the number of turns ΔN of the voltage regulating grid-side coil is obtained by Equation 1:

[0016] ΔN = [N2 - N1] (1)

[0017] where N1 is the number of turns of the grid-side coil corresponding to the first gear, and N2 is the number of turns of the grid-side coil corresponding to the second gear;

[0018] The N1 and N2 are obtained by Equations 2.1 and 2.2 respectively:

[0019]

[0020]

[0021] where U 网 is the fixed phase voltage on the grid side, e t1 is the turn electromotive force corresponding to the first voltage, and e t2 is the turn electromotive force corresponding to the second voltage.

[0022] Optionally, the values of e t1 and e t2 are obtained by Formulas 3.1 and 3.2:

[0023]

[0024]

[0025] where U1 is the first phase voltage on the valve side, U2 is the second phase voltage on the valve side, and n is the number of turns of the second valve-side coil.

[0026] Optionally, the number of turns of the first valve-side coil is 26, and the number of turns of the second valve-side coil is 45.

[0027] The technical solution provided by the present invention has the following advantages compared with the prior art:

[0028] 1) The gear adjustment is convenient and flexible: it can not only conveniently achieve the voltage interchange between 485V and 590V at the valve side output, but also meet the gear adjustment requirements of the primary side network voltage tapping range;

[0029] 2) It is convenient for maintenance and management: the copper foil on the valve side does not change in structure during the entire voltage conversion, the main structure of the transformer does not change, the position of the external connection wires of the network side coil does not change, and there are no redundant structural parts, which is convenient for on-site operation, maintenance and management;

[0030] 3) The cost is reduced: during the turns conversion process, it is only necessary to ensure that the core magnetic density is not saturated in the linear working area. Compared with the method of increasing copper foil on the valve side for voltage conversion, the cost is significantly reduced.

[0031] 4) The performance of the transformer is stable: There is no obvious difference between this type of structure coil and the traditional traction rectifier transformer coil in terms of turns selection, structural design, current density, magnetic density selection, etc., which can ensure that characteristic parameters such as the no-load line voltage unbalance rate, half-through impedance unbalance rate, and voltage transformation ratio of the two coils on the valve side meet the relevant requirements of national standards;

[0032] 5) The performance of the transformer is stable: The turns and structures of the axially double-split parallel network side coils are completely the same, and there will be no circulating current during the operation of the transformer, improving the reliability of the transformer operation;

[0033] 6) The structure of the rectifier transformer is compact: it can be integrated and used in a DC traction substation box. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the valve side coil of a variable-flux voltage-regulating rectifier transformer for electric vehicles described in an embodiment of the present invention;

[0035] Figure 2 It is a schematic diagram of the network side coil of a variable-flux voltage-regulating rectifier transformer for electric vehicles described in an embodiment of the present invention;

[0036] Figure 3 It is a schematic diagram of a variable-flux voltage-regulating rectifier transformer for electric vehicles described in an embodiment of the present invention;

[0037] Figure 4 It is a schematic diagram of the adjustment panel of a variable-flux voltage-regulating rectifier transformer for electric vehicles under the first voltage described in an embodiment of the present invention;

[0038] Figure 5 It is a schematic diagram of the adjustment panel of a variable-flux voltage-regulating rectifier transformer for electric vehicles under the second voltage described in an embodiment of the present invention;

[0039] Figure 6 This is the voltage regulation schematic diagram of a variable flux voltage regulation and rectification transformer for trams in an embodiment of the present invention.

[0040] As shown in the figure:

[0041] 10 - valve side coil; 101 - first valve side coil; 102 - second valve side coil; 20 - line side coil; 201 - first line side coil; 202 - second line side coil; 301 - tap board; 3011 - incoming line terminal; 3012 - first voltage outgoing terminal; 3013 - second voltage outgoing terminal; 3014 - first tap terminal; 3015 - second tap terminal; 302 - diagonal stay wire. Specific embodiments

[0042] For ease of understanding, the variable flux voltage regulation and rectification transformer for trams will be described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0043] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation and positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0044] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0045] As Figure 1-2 shown, the variable flux voltage regulation and rectification transformer for trams includes a three-phase coil with a double-split four-coil structure. The three-phase coil is divided into a valve side coil 10 and a line side coil 20 corresponding to the valve side coil 10. The valve side coil 10 is split into two parts: three star-connected first valve side coils 101 and three delta-connected second valve side coils 102. The line side coil 20 is split into three delta-connected first line side coils 201 and three delta-connected second line side coils 202. In each phase coil, the first line side coil 201 and the second line side coil 202 are connected in parallel;

[0046] Reference Figure 2 As shown, the first line-side coil 201 or the second line-side coil 202 is provided with a first gear corresponding to the first voltage of the network valve and a second gear corresponding to the second voltage of the network valve. The first voltage is higher than the second voltage. Different turn electromotive forces of the line-side coil 20 are obtained by changing the gear of the line-side coil 20.

[0047] According to the transformer characteristics, the turn electromotive force of the line-side coil 20 is equal to the turn electromotive force of the valve-side coil 10. That is to say, on the premise that the input voltage remains unchanged, by changing the number of turns of the line-side coil 20 connected to the circuit, the turn electromotive force of the line-side coil 20 can be changed, and the turn electromotive force of the valve-side coil 10 will also change accordingly. And the number of turns of the valve-side coil 10 connected remains unchanged, then the output voltage of the valve-side coil 10 will change in direct proportion to the turn electromotive forces on both sides, thus achieving the purpose of realizing the transformation of the secondary output voltage of the transformer. That is to say, as long as the number of turns of the line-side coil 20 connected is controlled well, the output voltage of the valve-side coil 10 can be controlled.

[0048] It should be noted that during the process of changing the two turn electromotive forces, the magnetic flux density of the transformer also changes accordingly, and under the two voltage regulation methods, the magnetic flux density cannot be saturated. The transformation of the valve-side voltage is realized through the electromagnetic induction change composed of the line-side coil 20 and the iron core. Since the coil in the present invention is a double-split four-coil structure, on the basis of realizing the variable magnetic flux voltage regulation method on the line side, the number of turns of the two parallel coils should be set separately to avoid the occurrence of circulating current between the upper and lower coils due to different numbers of turns. With the change of the turn electromotive force, the magnetic flux of the rectifier transformer will change. In other words, the transformation of the valve-side voltage is realized through the electromagnetic induction change composed of the line-side coil 20 and the iron core. Therefore, this voltage regulation method is called variable magnetic flux voltage regulation.

[0049] Specifically, the calculation of its number of turns is as follows:

[0050] First, determine the turn electromotive force e corresponding to the first voltage t1 and the turn electromotive force e corresponding to the second voltage t2 ,

[0051] e t1 and e t2 values are obtained through Formulas 3.1 and 3.2:

[0052]

[0053]

[0054] Among them, U1 is the first-phase voltage of the valve side, U2 is the second-phase voltage of the valve side, and n is the number of turns of the valve-side coil 10.

[0055] Then, when the valve-side coil 10 remains unchanged, find the number of turns N1 and N2 of the line-side coil 20 under the first voltage and the second voltage respectively.

[0056] N1 and N2 are obtained through Formulas 2.1 and 2.2 respectively:

[0057]

[0058]

[0059] where U 网 is the fixed-phase voltage on the grid side. It should be noted that since the grid-side coil 20 is a parallel connection of two coils, the number of turns here is the number of turns on one coil.

[0060] Finally, when determining the adjusted voltage, the number of turns ΔN of the adjustment coil is

[0061] The number of turns ΔN of the voltage-regulating coil is obtained through Formula 1:

[0062] ΔN = [N2 - N1] (1)

[0063] Thus, the number of turns of the coil that needs to be adjusted when switching the voltage can be determined. And, according to the position corresponding to the number of turns of the voltage-regulating coil in the grid-side coil 20, tap terminals are set to facilitate the adjustment of the voltage.

[0064] In a specific embodiment of the present invention, the number of turns of the first valve-side coil 101 is 26, and the number of turns of the second valve-side coil 102 is 45. Since the turn ratio of the valve-side △-connected coil to the Y-connected coil is 1:√3, but the number of turns of the coil must be an integer, there must be an no-load voltage difference between the valve-side coils 101 and 102. According to the national standard, the no-load voltage difference between the valve-side coils 101 and 102 shall not exceed 0.3%. Therefore, in the present invention, the number of turns of the valve-side △-connected coil is 45 turns, and the number of turns of the Y-connected coil is 26 turns. The no-load voltage difference between the valve-side coils 101 and 102 is (26×√3 - 45) / 45×100% = 0.075%, which is much less than 0.3% and far less than the national standard requirements.

[0065] Such as Figure 3As shown, in the present invention, the gear is adjusted through a voltage regulating panel. The voltage regulating panel includes a wiring board, an incoming line terminal 3011 led out from the grid-side coil 20 and arranged on the wiring board, a first voltage outgoing line terminal 3012, a second voltage outgoing line terminal 3013, and a tapping board 301 connecting the terminals; when the tapping board 301 connects the first voltage outgoing line terminal 3012 and the second voltage outgoing line terminal 3013, the voltage regulating coil between the first voltage outgoing line terminal 3012 and the second voltage outgoing line terminal 3013 is short-circuited, and the power is taken out from the first voltage outgoing line terminal 3012, which is the first gear. When the connection between the first voltage outgoing line terminal 3012 and the second voltage outgoing line terminal 3013 is disconnected, the voltage regulating coil between the first voltage outgoing line terminal 3012 and the second voltage outgoing line terminal 3013 is connected, and the power is taken out from the second voltage outgoing line terminal 3013, which is the second gear.

[0066] In the present invention, the valve-side coil 10 does not change in structure during the entire voltage conversion, the main structure of the transformer does not change, the position of the external connection line of the grid-side coil 20 does not change, and there are no redundant structural parts, which is convenient for on-site operation, maintenance and management.

[0067] As Figure 3-5 shown, the voltage regulating panel further includes a plurality of first tapping terminals 3014 for regulating the voltage of the first gear and a plurality of second tapping terminals 3015 for regulating the voltage of the second gear. The first tapping terminals 3014 are led out from the first tapping gear coil between the incoming line terminal 3011 and the first voltage outgoing line terminal 3012, and the second tapping terminals 3015 are led out from the second tapping gear coil in the voltage regulating coil.

[0068] Short-circuit the voltage regulating coil and disconnect the second tapping terminal 3015, and then connect the corresponding first tapping terminal 3014 through the tapping board 301 to regulate the voltage of the first gear; connect the voltage regulating coil and adjust the first tapping gear to the maximum, and then connect the corresponding second tapping terminal 3015 through the tapping board 301 to regulate the voltage of the second gear.

[0069] The voltage regulation range of the first tapping terminal 3014 or the second tapping terminal 3015 is ±5% or ±2×2.5%.

[0070] Specifically, in a specific embodiment of the present invention, the first voltage is 590V and the second voltage is 485V. Referring to Figure 4-6 shown, the high-voltage ABC three-phase structures of the grid-side coil 20 are completely the same, and only one phase is selected for illustration:

[0071] Referring to Figure 4 and Figure 6, 2 - 5 are the first incoming line voltage regulating terminals 3014, 6 - 9 are the second incoming line terminals 3015, X1’ is the first voltage outgoing terminal 3012, X1” is the second voltage outgoing terminal 3013, and both A1 and A2 are the incoming line terminals 3011 of the rectifier transformer.

[0072] When the required voltage is 590V, the part of the access circuit required is A1 - X”, and it is connected using the diagonal wire 302. Among them, for X1” - X1’, the outgoing terminals corresponding to X1” and X1’ on the voltage regulating panel are short - circuited using a tapping copper plate, so that this part of the winding is withdrawn from the line - side coil 20. Since the line - side coil 20 is composed of two completely symmetrical coils in parallel, the same wiring can be done for the other coil.

[0073] According to the ±5% regulation requirement stipulated by the national standard, the voltage can be finely adjusted by adjusting the number of turns of the second incoming line terminal 3011. Since when the output voltage is 590V, the coil connected is A1 - X1’, the first tapping terminal 3014 can be adjusted to adjust the voltage.

[0074] Specifically, referring to Figure 6 As shown, when 6 - 7 in the first tapping terminal 3014 is short - circuited, the coil between the two terminals is short - circuited and thus withdrawn from the line - side coil 20, and the line - side coil 20 reduces by n1 turns; when 7 - 8 in the first tapping terminal 3014 is short - circuited, the coil between the two terminals is short - circuited and thus withdrawn from the line - side coil 20, and the line - side coil 20 reduces by n2 turns; when 8 - 9 in the first tapping terminal 3014 is short - circuited, the coil between the two terminals is short - circuited and thus withdrawn from the line - side coil 20, and the line - side coil 20 reduces by n3 turns, and n1 > n2 > n3. When the input voltage remains unchanged, the turn - electromotive forces of the three are successively reduced, that is, the regulation within the range of ±5% of the target voltage can be achieved. It should be noted that the positions of several first tapping terminals 3014 are calculated in advance, and different short - circuiting methods can obtain different voltages, not limited to the above - mentioned three - stage voltage regulation. The number of terminals can also be increased continuously to meet the requirement of ±2×2.5% of the line - side tapping positions, making it more convenient for users to use.

[0075] Referring to Figure 5 and Figure 6 As shown, when the user needs to adjust the output voltage to 485V, the number of turns of the valve - side coil 10 remains unchanged, the turn - electromotive force of the valve - side will become smaller, so the turn - electromotive force of the line - side will also become smaller. Since the line - side input voltage level remains unchanged, more turns need to be connected to the circuit to meet the requirement of the reduced output valve - side voltage.

[0076] Here, X1'-X1" needs to be connected to the transformer circuit, so X1' and X1" are in a disconnected state. The tap position of the original 590V is adjusted to the maximum tap position, that is, all the coils between A1-X1' and A2-X2' are connected in series. That is to say, the tap plate 301 here is placed at the connection position of coils 7-8.

[0077] Similarly, when the output voltage is 485V, its tap position adjustment terminal is 2-5. The voltage can be adjusted in the same way as above to meet the adjustment requirement of ±5%. Terminals can also be continuously added to achieve the requirement of ±2×2.5% for the grid-side tap position.

[0078] In summary, the present invention can not only conveniently realize the voltage interchange between 485V and 590V on the valve side, but also meet the tap-changing requirements of the primary-side grid voltage tapping range. Compared with other rectifier transformers for adjusting the voltage level, the cost is reduced. During the turns transformation process, it is only necessary to ensure that the core magnetic density is not saturated, and it can be in the linear working region. Compared with the method of increasing copper foil on the valve side for voltage transformation, the cost is significantly reduced. The performance of the transformer is stable: There is no obvious difference between the coils of this structure and the coils of traditional traction rectifier transformers in terms of turn selection, structure design, current density, magnetic density selection, etc., which can ensure that the characteristic parameters such as the no-load line voltage unbalance rate, half-through impedance unbalance rate, and voltage ratio of the two coils on the valve side meet the relevant requirements of national standards; and the turns and structures of the axially double-split parallel high-voltage coils are completely the same, and no circulating current will occur during the operation of the transformer, improving the reliability of the transformer operation; the product structure of the rectifier transformer is compact and can be integrated for use in a DC traction substation box.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A variable-flux voltage-regulating and rectifying transformer for electric vehicles, characterized in that, Comprising: A three-phase coil with a double-split four-coil structure, the three-phase coil being divided into a valve-side coil and a line-side coil corresponding to the valve-side coil. The valve-side coil is split into two parts, namely three star-connected first valve-side coils and three delta-connected second valve-side coils. The line-side coil is split into three delta-connected first line-side coils and three delta-connected second line-side coils. In each phase coil, the first line-side coil and the second line-side coil are connected in parallel; the first line-side coil or the second line-side coil is provided with a first gear corresponding to the first line-valve voltage and a second gear corresponding to the second line-valve voltage. The first voltage is higher than the second voltage. Different turn electromotive forces of the line-side coil are obtained by changing the gear of the line-side coil; the gear is adjusted through a voltage regulating panel. The voltage regulating panel includes a wiring board, an incoming line terminal led out from the line-side coil and arranged on the wiring board, a first voltage outgoing line terminal, a second voltage outgoing line terminal, and a tapping board connecting the terminals; when the tapping board connects the first voltage outgoing line terminal and the second voltage outgoing line terminal, the voltage regulating coil between the first voltage outgoing line terminal and the second voltage outgoing line terminal is short-circuited, and the power is taken out from the first voltage outgoing line terminal, which is the first gear; when the connection between the first voltage outgoing line terminal and the second voltage outgoing line terminal is disconnected, the voltage regulating coil between the first voltage outgoing line terminal and the second voltage outgoing line terminal is connected in, and the power is taken out from the second voltage outgoing line terminal as the second gear.

2. The variable-flux voltage regulating and rectifying transformer for tram according to claim 1, wherein Comprising: The voltage regulating panel further includes a plurality of first tapping terminals for regulating the voltage of the first gear and a plurality of second tapping terminals for regulating the voltage of the second gear. The first tapping terminals are led out from a first tapping gear coil between the incoming line terminal and the first voltage outgoing line terminal, and the second tapping terminals are led out from a second tapping gear coil in the voltage regulating coil.

3. A variable-flux voltage-regulating and rectifying transformer for tramcars according to claim 1, characterized in that, Comprising: Short-circuit the voltage regulating coil and disconnect the second tapping terminals, and then connect the corresponding first tapping terminals through the tapping board to regulate the voltage of the first gear; connect in the voltage regulating coil and adjust the first tapping gear to the maximum, and then connect the corresponding second tapping terminals through the tapping board to regulate the voltage of the second gear.

4. The variable-flux voltage regulating and rectifying transformer for tram according to claim 3, wherein Comprising: The voltage regulation range of the first tapping terminal or the second tapping terminal is ±5% or ±2×2.5%.

5. A variable-flux voltage regulating and rectifying transformer for a tram, characterized in that, Comprising: The number of turns ΔN of the voltage regulating line-side coil is obtained by formula 1: ΔN = [N2 - N1] (1) Where N1 is the number of turns of the line-side coil corresponding to the first gear, and N2 is the number of turns of the line-side coil corresponding to the second gear; The N1 and N2 are respectively obtained by formula 2.1 and 2.2: Among them, U 网 is the fixed-phase voltage on the grid side, e t1 is the turn electromotive force corresponding to the first voltage, e t2 is the turn electromotive force corresponding to the second voltage.

6. The variable-flux voltage-regulating and rectifying transformer for tram according to claim 5, characterized in that, Comprising: The said e t1 and e t2 values are obtained through Formulas 3.1 and 3.2: Wherein, U1 is the first-phase voltage of the valve side, U2 is the second-phase voltage of the valve side, and n is the number of turns of the second valve-side coil.

7. The variable-flux voltage-regulating and rectifying transformer for tram according to claim 1, characterized in that Comprising: The number of turns of the first valve-side coil is 26, and the number of turns of the second valve-side coil is 45.

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