Transformer three-phase circuit and low noise energy-saving and environmentally friendly low temperature rise transformer

Abstract

The present invention discloses a three-phase transformer circuit and a transformer, wherein the circuit includes a phase a circuit, a phase b circuit and a phase c circuit including winding resistance and lead resistance, wherein the winding resistance includes resistance R3, resistance R4 and resistance R5, and the lead resistance includes resistance R2, resistance R6, resistance R1A, resistance R1B, resistance R1C and resistance R1D, wherein the resistance R1B leads the neutral point to ground from the middle; the three-phase circuit includes a connection circuit of phase resistances R0a, R0b and R0c; the three-phase circuit also includes a connection circuit of line resistances Rab, Rbc and Rac; the three-phase circuit is used to reduce the three-phase resistance unbalance rate. Through the technical solution provided by the present invention, the three-phase DC resistance unbalance rate of the transformer is reduced, the weight of the lead conductor is reduced, the transformer cost is reduced, the winding overvoltage and the circulating current generated between the winding phases are reduced, the circulating current loss between the windings is reduced, and the temperature rise of the windings is reduced, so as to achieve the effects of low noise, energy saving and consumption reduction and increase the life of the transformer.

Description

Technical Field

[0001] The invention relates to the technical field of transformers, and in particular to a transformer three-phase circuit and a low-noise, energy-saving, environmentally friendly and low-temperature-rise transformer. Background Art

[0002] See also Figure 1 In the prior art, the three-phase circuit of the transformer includes a'phase circuit, b'phase circuit and c'phase circuit, R3', R4' and R5' are winding resistances, R2', R6', R11' and R12' are lead resistances, wherein R11' leads the neutral point from the middle to ground. The phase resistance R0'a' of the a' phase circuit is R2', R3' and half R11' connected in series; the phase resistance R0'b' of the b' phase circuit is R4' and half R11' connected in series; the phase resistance R0'c' of the c' phase circuit is R6', R5', R12' and half R11' connected in series; the line resistance Ra'b' is R2', R3', R11', R4' connected in series; the line resistance Ra'c' is R2', R3', R11', R12', R5', R6' connected in series; the line resistance Rb'c' is R4', R12', R5', R6' connected in series. The existing three-phase circuit has a three-phase DC resistance imbalance rate that easily exceeds the limit specified by the national standard. The calculated line resistance difference and phase resistance difference are large, causing the neutral point of the transformer to shift and the voltage of the three-phase winding to be unbalanced. This voltage asymmetry will increase the winding overvoltage, cause the transformer noise to increase, and increase the circulating current between the phases of the transformer winding, increasing its own loss. At the same time, it will increase the temperature rise of the winding and reduce the service life of the transformer.

[0003] According to Article 6.2 of the national standard GB / T10228-2015 "Technical Parameters and Requirements for Dry-Type Power Transformers": For distribution transformers of 2500kVA and below, the DC resistance unbalance rate of the windings: no more than 4% for phases and no more than 2% for lines; GB / T 6451-2015 "Technical Parameters and Requirements for Oil-Immersed Power Transformers" 4.3.2 stipulates: The DC resistance unbalance rate of the windings: no more than 4% for phases and no more than 2% for lines.

[0004] For distribution transformers with a larger capacity of more than 1000kVA, the larger the capacity, the fewer turns of the low-voltage winding, the shorter the wire length and the larger the cross-sectional area, so the resistance value of the winding is smaller. At the same time, the larger the capacity, the longer the lead length, the greater the lead resistance, and the greater the ratio of lead resistance to total resistance. Therefore, the resistance of the lead has a greater impact on the three-phase resistance unbalance rate. According to the design of the lead structure of the traditional distribution transformer and the winding resistance and lead resistance circuit, in order to meet the requirements of the national standard limit, it is necessary to significantly increase the cross-sectional area of ​​the lead conductor and reduce the resistance value of the lead, which requires a large material cost. At the same time, due to the improvement of the performance of transformer materials and the manufacturing level, the capacity of the distribution transformer has greatly exceeded the limit of 2500kVA listed in the standard, so the situation where the resistance unbalance rate caused by the lead structure exceeds the limit specified in the national standard is more prominent. Summary of the invention

[0005] The present invention provides a transformer three-phase circuit and a low-noise energy-saving and environmentally friendly low-temperature rise transformer, aiming to reduce the three-phase resistance unbalance rate, reduce the problems caused by the three-phase resistance unbalance, reduce the cost and extend the life of the transformer.

[0006] To achieve the above object, the present invention provides a three-phase transformer circuit, the three-phase circuit comprising an a-phase circuit, a b-phase circuit and a c-phase circuit including winding resistance and lead resistance, the winding resistance comprising a resistor R3, a resistor R4 and a resistor R5, the lead resistance comprising a resistor R1A, a resistor R1B, a resistor R1C and a resistor R1D, the resistor R1B is connected from the middle to the neutral point and grounded; the phase resistance R0a of the a-phase circuit is R1A, R1C, R1D, and one-half R1B connected in series and then connected in parallel with one-half R1B, then Then it is connected in series with R3; the phase resistance R0c of the c-phase circuit is the series connection of R1C, R1A, and half of R1B and the series connection of R1D and half of R1B in parallel, and then connected in series with R5; the phase resistance R0b of the b-phase circuit is the series connection of R1C, R1D, and half of R1B and the series connection of R1A and half of R1B in parallel, and then connected in series with R4; the three-phase circuit also includes a connection circuit of line resistances Rab, Rbc and Rac; the three-phase circuit is used to reduce the imbalance rate of three-phase resistance.

[0007] Preferably, the line resistor Rab is R1B, R1D, and R1C connected in series, connected in parallel with R1A, and then connected in series with R3 and R4.

[0008] Preferably, the line resistor Rbc is R1A, R1B, and R1D connected in series, connected in parallel with R1C, and then connected in series with R4 and R5.

[0009] Preferably, the line resistance Rac is a series connection of R1A and R1C in parallel with a series connection of R1B and R1D, and then connected in series with R3 and R5.

[0010] Preferably, the a-phase circuit, the b-phase circuit and the c-phase circuit are in a star connection structure.

[0011] Preferably, the lead resistor further includes a resistor R2 and a resistor R6, wherein the resistor R2 is connected in series with the resistor R3, and the resistor R6 is connected in series with the resistor R5.

[0012] Preferably, the resistor R2 and the resistor R6 have the same size, and the resistor R3, the resistor R4 and the resistor R5 have the same size.

[0013] Preferably, the three-phase circuit is a three-phase winding DC circuit.

[0014] At the same time, the present invention provides a low-noise, energy-saving, environmentally friendly, low-temperature rise transformer, and the transformer includes the above-mentioned transformer three-phase circuit.

[0015] Compared with the prior art, the present invention provides a transformer three-phase circuit and a low-noise, energy-saving, environmentally friendly and low-temperature-rise transformer. By changing the design of the winding resistance and the lead resistance circuit, the three-phase DC resistance unbalance rate of the transformer is reduced, the weight of the lead conductor is reduced, the transformer cost is reduced, the three-phase winding voltage imbalance caused by the offset of the transformer neutral point is reduced, the transformer noise caused by the winding overvoltage is reduced, and the circulating current between the winding phases caused by the three-phase DC resistance imbalance is reduced. The circulating current loss between the windings and the temperature rise of the windings can be reduced, thereby achieving the effect of low noise, energy saving and consumption reduction and increasing the life of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A circuit diagram of a three-phase circuit of a transformer 1 in the prior art;

[0017] Figure 2 A circuit diagram of a three-phase transformer circuit provided in Embodiment 1 of the present invention;

[0018] Figure 3 A circuit diagram of a three-phase circuit of a transformer 2 in the prior art;

[0019] Figure 4 This is a circuit diagram of a transformer three-phase circuit provided in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] See also Figure 1 The three-phase circuit of the transformer 1 in the prior art includes a'phase circuit, b'phase circuit and c'phase circuit, R3', R4' and R5' are winding resistances, R2', R6', R11' and R12' are lead resistances, wherein R11' leads the neutral point from the middle to ground. The phase resistance R0'a' of the a' phase circuit is R2', R3' and half R11' connected in series; the phase resistance R0'b' of the b' phase circuit is R4' and half R11' connected in series; the phase resistance R0'c' of the c' phase circuit is R6', R5', R12' and half R11' connected in series; the line resistance Ra'b' is R2', R3', R11', R4' connected in series; the line resistance Ra'c' is R2', R3', R11', R12', R5', R6' connected in series; the line resistance Rb'c' is R4', R12', R5', R6' connected in series. Specifically, the resistance of resistor R2' is set to r2, the resistance of resistor R3' is set to r3, the resistance of resistor R4' is set to r4, the resistance of resistor R5' is set to r5, the resistance of resistor R6' is set to r6, the resistance of resistor R11' is set to r1, and the resistance of resistor R12' is set to r1, wherein r2=r6, r3=r4=r5=R.

[0022] Calculate the line resistance difference as:

[0023] Ra'b'=R2'+R3'+R11'+R4'=r2+R+r1+R=r2+2R+r1

[0024] Rb'c'=R6'+R5'+R12'+R4'=r2+R+r1+R=r2+2R+r1

[0025] Ra'c'=R2'+R3'+R11'+R12'+R5'+R6'=r2+R+r1+r1+R+r2=2R+2r1+2r2

[0026] Then the line resistance difference of Ra'c', Ra'b', and Rb'c' is:

[0027] Ra'c'-Ra'b'=r1+r2

[0028] Ra'b'-Rb'c'=0

[0029] Ra'c'-Rb'c'=r1+r2

[0030] The maximum difference in line resistance is: r1+r2

[0031] Calculate the phase resistance difference as:

[0032]

[0033]

[0034]

[0035] Then the phase resistance difference of R0'a', R0'b', and R0'c' is:

[0036] R0'c'-R0'b'=r1+r2

[0037] R0'c'-R0'a'=r1

[0038] R0'a'-R0'b'=r2

[0039] The maximum difference in phase resistance is: r1+r2

[0040] See also Figure 2 A three-phase transformer circuit is provided in a first embodiment of the present invention, wherein the three-phase circuit comprises an a-phase circuit, a b-phase circuit and a c-phase circuit including winding resistance and lead resistance, and the a-phase circuit, the b-phase circuit and the c-phase circuit are in a star connection structure; preferably, the three-phase circuit is a three-phase winding DC circuit.

[0041] The winding resistors include resistors R3, R4 and R5, and the lead resistors include resistors R2, R6, R1A, R1B, R1C and R1D, wherein the resistor R1B is connected from the middle to a neutral point for grounding; the phase resistor R0a of the a-phase circuit is a series connection of R1A, R1C, R1D and half R1B, which is then connected in parallel with half R1B, and then connected in series with R2 and R3; the phase resistor R0c of the c-phase circuit is a series connection of R1C, R1A and half R1B, which is connected in parallel with a series connection of R1D and half R1B, and then connected in series with R6 and R5; the phase resistor R0b of the b-phase circuit is a series connection of R1C, R1D and half R1B, which is connected in parallel with a series connection of R1A and half R1B, and then connected in series with R4.

[0042] The three-phase circuit also includes a connection circuit of line resistors Rab, Rbc and Rac; the line resistor Rab is R1B, R1D, and R1C connected in series and then connected in parallel with R1A, and then connected in series with R2, R3 and R4; the line resistor Rbc is R1A, R1B, and R1D connected in series and then connected in parallel with R1C, and then connected in series with R4, R5 and R6; the line resistor Rac is R1A and R1C connected in series and then connected in parallel with R1B and R1D, and then connected in series with R2, R3, R5 and R6.

[0043] Specifically in this embodiment, the resistance of resistor R2 is set to r2, the resistance of resistor R3 is set to r3, the resistance of resistor R4 is set to r4, the resistance of resistor R5 is set to r5, the resistance of resistor R6 is set to r6, the resistance of resistor R1A is set to 2r1, the resistance of resistor R1B is set to 2r1, the resistance of resistor R1C is set to 2r1, and the resistance of resistor R1D is set to 2r1, wherein r2=r6, r3=r4=r5=R.

[0044] Calculate the line resistance difference as:

[0045]

[0046]

[0047]

[0048]

[0049] The line resistance difference of Rac, Rab, and Rbc is:

[0050]

[0051]

[0052] Rab-Rbc=0 line resistance maximum difference is:

[0053] Calculate the phase resistance difference as:

[0054]

[0055]

[0056]

[0057]

[0058] Then the phase resistance difference of R0a, R0b, and R0c is:

[0059] R0c-R0a=r1

[0060] R0c-R0b=r2

[0061] R0b-R0a=r1-r2

[0062] The maximum difference in phase resistance is: r1

[0063] From the above calculation, it can be seen that the maximum difference in line resistance is reduced compared with the existing technology. The maximum difference in phase resistance is reduced by r2 compared with the prior art.

[0064] In actual production, before the improvement, resistors R11 and R12 are one-lead lower conductors, R2' and R6' are two-lead upper conductors, after the improvement, R2 and R6 are two-lead upper conductors, resistors R1A and R1C are the first lower conductor, resistors R1D and R1B are the second lower conductor, the length and cross-sectional area of ​​the first lower conductor and the second lower conductor are equal, and the length is the same as the length of the lower conductor before the improvement, but the cross-sectional area is half of the lower conductor before the improvement. In general, the length of the r1 lower conductor is close to twice the length of the r2 upper conductor. For ease of analysis and comparison, r1 = 2r2.

[0065] but:

[0066]

[0067]

[0068] From the above analysis, it can be seen that with the same amount of lead conductor, the unbalance rate of transformer phase and line resistance can be reduced by one third, that is to say, with the same resistance unbalance rate, one third of the conductor used for the lead can be saved. At the same time, the calculated line resistance difference and phase resistance difference become smaller, which reduces the neutral point offset of the transformer, and can reduce the three-phase winding voltage imbalance caused by the neutral point offset of the transformer, thereby reducing the transformer noise caused by winding overvoltage, and reducing the circulating current between the winding phases caused by the three-phase DC resistance unbalance, which can reduce the circulating current loss between the windings and reduce the temperature rise of the windings, achieving the effect of low noise, energy saving and consumption reduction and increasing the life of the transformer.

[0069] See also Figure 3The three-phase circuit of the transformer 2 in the prior art includes a' phase circuit, b' phase circuit and c' phase circuit, R3', R4' and R5' are winding resistances, R11' and R12' are lead resistances, wherein R11' leads the neutral point from the middle to ground. The phase resistance R0'a' of the a' phase circuit is R3' and one-half R11' connected in series; the phase resistance R0'b' of the b' phase circuit is R4' and one-half R11' connected in series; the phase resistance R0'c' of the c' phase circuit is R5', R12' and one-half R11' connected in series; the line resistance Ra'b' is R3', R11', R4' connected in series; the line resistance Ra'c' is R3', R11', R12', R5' connected in series; the line resistance Rb'c' is R4', R12', R5' connected in series. Specifically, the resistance of the resistor R3' is set to r3, the resistance of the resistor R4' is set to r4, the resistance of the resistor R5' is set to r5, the resistance of the resistor R11' is set to r1, and the resistance of the resistor R12' is set to r1, wherein r3=r4=r5=R.

[0070] Calculate the line resistance difference as:

[0071] Ra'b'=R3'+R11'+R4'=R+r1+R=2R+r1

[0072] Rb'c'=R5'+R12'+R4'=R+r1+R=2R+r1

[0073] Ra'c'=R3'+R11'+R12'+R5'=R+r1+r1+R=2R+2r1

[0074] Then the line resistance difference of Ra'c', Ra'b', and Rb'c' is:

[0075] Ra'c'-Ra'b'=r1

[0076] Ra'b'-Rb'c'=0

[0077] Ra'c'-Rb'c'=r1

[0078] The maximum difference in line resistance is: r1

[0079] Calculate the phase resistance difference as:

[0080]

[0081]

[0082]

[0083] Then the phase resistance difference of R0'a', R0'b', and R0'c' is:

[0084] R0'c'-R0'b'=r1

[0085] R0'c'-R0'a'=r1

[0086] R0'a'-R0'b'=0

[0087] The maximum difference in phase resistance is: r1

[0088] See also Figure 4 Embodiment 2 of the present invention provides a three-phase transformer circuit, wherein the three-phase circuit includes an a-phase circuit, a b-phase circuit and a c-phase circuit including winding resistance and lead resistance, and the a-phase circuit, the b-phase circuit and the c-phase circuit are in a star connection structure; preferably, the three-phase circuit is a three-phase winding DC circuit.

[0089] The winding resistors include resistors R3, R4 and R5, and the lead resistors include resistors R1A, R1B, R1C and R1D, wherein the resistor R1B is connected to ground with a neutral point drawn out from the middle; the phase resistor R0a of the a-phase circuit is a series connection of R1A, R1C, R1D and half R1B, which is then connected in parallel with half R1B, and then connected in series with R3; the phase resistor R0c of the c-phase circuit is a series connection of R1C, R1A and half R1B, which is then connected in parallel with R1D and half R1B, and then connected in series with R5; the phase resistor R0b of the b-phase circuit is a series connection of R1C, R1D and half R1B, which is then connected in parallel with R1A and half R1B, and then connected in series with R4.

[0090] The three-phase circuit also includes a connection circuit of line resistors Rab, Rbc and Rac; the line resistor Rab is R1B, R1D, and R1C connected in series and then connected in parallel with R1A, and then connected in series with R3 and R4; the line resistor Rbc is R1A, R1B, and R1D connected in series and then connected in parallel with R1C, and then connected in series with R4 and R5; the line resistor Rac is R1A and R1C connected in series and then connected in parallel with R1B and R1D, and then connected in series with R3 and R5.

[0091] Specifically in this embodiment, the resistance of resistor R3 is set to r3, the resistance of resistor R4 is set to r4, the resistance of resistor R5 is set to r5, the resistance of resistor R1A is set to 2r1, the resistance of resistor R1B is set to 2r1, the resistance of resistor R1C is set to 2r1, and the resistance of resistor R1D is set to 2r1, wherein r3=r4=r5=R.

[0092] Calculate the line resistance difference as:

[0093]

[0094]

[0095]

[0096]

[0097] The line resistance difference of Rac, Rab, and Rbc is:

[0098]

[0099]

[0100] Rab-Rbc=0 line resistance maximum difference is:

[0101] Calculate the phase resistance difference as:

[0102]

[0103]

[0104]

[0105]

[0106] Then the phase resistance difference of R0a, R0b, and R0c is:

[0107] R0c-R0a=r1

[0108] R0c-R0b=0

[0109] R0b-R0a=r1

[0110] The maximum difference in phase resistance is: r1

[0111] It can be seen from the above calculation that the maximum difference in line resistance of the second embodiment is reduced by 1.1% compared with the maximum difference in line resistance of the second transformer in the prior art.

[0112] Comparing the reduction value of the maximum line resistance difference of the second embodiment compared with the maximum line resistance difference of the second transformer in the prior art with the maximum line resistance difference of the second transformer in the prior art, we can obtain:

[0113]

[0114] From the above analysis, it can be seen that with the same amount of lead conductor, the transformer line resistance unbalance rate can be reduced by one half, that is to say, with the same line resistance unbalance rate, one half of the conductor used for the lead can be saved. At the same time, the calculated line resistance difference and phase resistance difference become smaller, which reduces the neutral point offset of the transformer, and can reduce the three-phase winding voltage imbalance caused by the transformer neutral point offset, thereby reducing the transformer noise caused by winding overvoltage, and at the same time can reduce the circulating current between the winding phases caused by the three-phase DC resistance unbalance, which can reduce the circulating current loss between the windings and reduce the temperature rise of the windings, achieving the effect of low noise, energy saving and consumption reduction and increasing the life of the transformer.

[0115] In addition, the present invention also provides a low-noise, energy-saving, environmentally friendly, low-temperature-rise transformer, which includes the above-mentioned transformer three-phase circuit.

[0116] Compared with the prior art, the present invention provides a transformer three-phase circuit and a low-noise, energy-saving, environmentally friendly, and low-temperature-rise transformer. By changing the design of the winding resistance and the lead resistance circuit, the three-phase DC resistance unbalance rate of the transformer is reduced, the weight of the lead conductor is reduced, the transformer cost is reduced, the three-phase winding voltage imbalance caused by the offset of the neutral point of the transformer is reduced, and the transformer noise caused by the winding overvoltage is reduced. At the same time, the circulating current between the winding phases caused by the three-phase DC resistance imbalance is reduced, the circulating current loss between the windings and the temperature rise of the windings can be reduced, and the effect of low noise, energy saving, and consumption reduction and increased transformer life is achieved.

[0117] The above description is only an implementation mode of the present invention. It should be pointed out that, for ordinary technicians in this field, improvements can be made without departing from the creative concept of the present invention, but these all belong to the protection scope of the present invention.

Claims

1. A three-phase transformer circuit, characterized in that: The three-phase circuit includes an a-phase circuit, a b-phase circuit and a c-phase circuit including winding resistances and lead resistances, wherein the winding resistances include resistances R3, R4 and R5, and the lead resistances include resistances R1A, R1B, R1C and R1D, wherein the resistance R1B is connected from the middle to the neutral point for grounding; the phase resistance R0a of the a-phase circuit is R1A, R1C, R1D, and one-half R1B connected in series, connected in parallel with one-half R1B, and then connected in series with R3; The phase resistance R0c of the c-phase circuit is a series connection of R1C, R1A, and half R1B, which is connected in parallel with a series connection of R1D and half R1B, and then connected in series with R5; the phase resistance R0b of the b-phase circuit is a series connection of R1C, R1D, and half R1B, which is connected in parallel with a series connection of R1A and half R1B, and then connected in series with R4; the three-phase circuit also includes a connection circuit of line resistances Rab, Rbc and Rac; the three-phase circuit is used to reduce the imbalance rate of the three-phase resistance.

2. The transformer three-phase circuit according to claim 1, characterized in that: The line resistor Rab is R1B, R1D, and R1C connected in series, connected in parallel with R1A, and then connected in series with R3 and R4.

3. The transformer three-phase circuit according to claim 1, characterized in that: The line resistor Rbc is R1A, R1B, and R1D connected in series, connected in parallel with R1C, and then connected in series with R4 and R5.

4. The transformer three-phase circuit according to claim 1, characterized in that: The line resistance Rac is a series connection of R1A and R1C in parallel with a series connection of R1B and R1D, and then connected in series with R3 and R5.

5. The transformer three-phase circuit according to claim 1, characterized in that: The a-phase circuit, the b-phase circuit and the c-phase circuit are in a star connection structure.

6. The transformer three-phase circuit according to claim 1, characterized in that: The lead resistor further includes a resistor R2 and a resistor R6, wherein the resistor R2 is connected in series with the resistor R3, and the resistor R6 is connected in series with the resistor R5.

7. The transformer three-phase circuit according to claim 6, characterized in that: The resistor R2 and the resistor R6 have the same size, and the resistor R3, the resistor R4 and the resistor R5 have the same size.

8. The transformer three-phase circuit according to claim 1, characterized in that: The three-phase circuit is a three-phase winding DC circuit.

9. A low-noise, energy-saving, environmentally friendly, low-temperature rise transformer, characterized in that: The transformer comprises a three-phase circuit using the transformer described in any one of claims 1 to 8.

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