CN102044923B - Neutral point grounding structure and method of delta junction winding - Google Patents

Abstract

The invention discloses a neutral point grounding structure of a delta connection winding and a method thereof, the delta connection winding is provided with a first phase winding, a second phase winding and a third phase winding, wherein a grounding winding with the number of turns 1/3 times that of the phase winding is added in at least one phase winding, the grounding winding comprises a first end grounded and a second end connected to a tap position with the number of turns 1/3 times that of one of the adjacent phase windings so as to generate a neutral point, and the voltage phase of the grounding winding is opposite to the voltage phase of the phase winding of the phase to which the grounding winding belongs. Through the neutral point grounding structure and the method thereof, when three phases are balanced, the voltages of any phase line to the neutral point are the same, and the problem derived from the fact that the three phases have different voltages to the ground due to the traditional triangular knot winding grounding method is solved.

Description

Neutral point grounding structure and method of delta junction winding

【Technical field】

The invention relates to a wire-connected winding structure and its method, in particular to a triangular-wire-connected winding structure with a neutral point and its method.

【Background technique】

倍。The connection methods of the three-phase winding are divided into triangle connection and Y-shaped connection. The insulation withstand voltage level of the Y-shaped tie-wire winding is low, but its disadvantage is that it provides a flow path for zero-phase-sequence current, third harmonics, and harmonics with multiples of three, which is detrimental to system power supply efficiency and quality. Although the triangular junction winding does not have the above-mentioned problems of harmonic and zero-phase sequence current flow, its insulation withstand voltage level must be higher, so that it can be used in the same voltage level as the Y-shaped junction winding with a lower insulation withstand voltage level. system. Delta-connected windings are also called delta-connected windings. Generally speaking, there are two grounding methods for traditional delta-connected windings. One is the line-grounded method, also known as One is the corner-grounded method, and the other is the mid-phase grounded method. Figure 1 shows the wire grounding method of the delta junction wire winding in the prior art. In the wire grounding method, one corner (corner) is grounded. The figure shows that the c-phase line is pulled out and grounded, so the corner connected to the corner is grounded. The phase line (phase line) to the ground voltage is the ground potential, and the voltage across the other two phase lines to the ground is the line voltage (line voltage). Figure 2 shows the mid-phase grounding method of the delta-connected winding in the prior art. In the mid-phase grounding method, the mid-tap of a certain phase winding is generally grounded. The figure shows that the a-phase line The midpoint tap of the phase winding between the phase line and the c-phase line is grounded, so the voltage across two phase lines to ground is only 1/2 of the line voltage, and the voltage across the other phase line to ground is 1/2 of the line voltage

times.

It can be seen from the above that the traditional grounding method of delta-connected windings will lead to inconsistencies in the three-phase line-to-ground voltages, and there are considerable differences, which also lead to many problems, including: motor control powered by delta-connected windings In the circuit, the phase line connected to the coil of the contactor is obviously affected by the position of the grounding point of the traditional grounding method, and it is easy to cause harm due to negligence.

【Content of invention】

The purpose of the present invention is to provide a neutral point grounding structure and method for delta-connected windings, which can improve the problem of inconsistency of three-phase line-to-ground voltages caused by traditional delta-connected winding grounding methods, and can improve the efficiency of delta-connected windings. The applicable withstand voltage level makes the triangular knot wire winding have its own advantages, and also has the advantages of the Y shape knot wire winding.

To achieve the above object, the present invention provides a neutral point grounding structure of a delta-connected winding, the delta-connected winding has first, second and third phase windings, wherein each phase winding has several turns respectively, In the three-phase winding, at least one phase winding is added with a ground winding whose number of turns is 1/3 times the number of turns of the phase winding, wherein the ground winding includes a first end for grounding, and a second end for connecting to an adjacent 1/3 times the number of turns of one of the phase winding taps to generate a neutral point, the voltage of the ground winding is opposite to the voltage of the phase winding of the phase to which the ground winding belongs. That means the phase difference between the two voltages is 180 degrees.

The present invention also provides a neutral point grounding structure of a delta-connected winding. The delta-connected winding has first, second and third phase windings, and each phase winding has several turns respectively. In the first 1. At least one phase winding in the second and third phase windings adds a grounding winding group, the grounding winding group is formed by parallel connection of at least two grounding windings whose turns are 1/3 times the number of turns of the phase winding respectively, and the grounding winding The group consists of a first terminal for grounding and a second terminal for connection to a 1/3 times the number of turns tap of one of the adjacent phase windings to create a neutral point, the voltage of the grounded winding group being the same as that of the grounded winding The voltage of the phase winding of the phase to which the group belongs is opposite. That means the phase difference between the two voltages is 180 degrees.

The present invention also provides a neutral point grounding method for a delta-connected winding, the delta-connected winding has first, second and third phase windings, and each phase winding has several turns, the method includes the following Steps: adding a grounding winding whose number of turns is 1/3 times the number of turns of the phase winding in at least one phase winding of the three-phase winding; grounding the first end of the grounding winding; and connecting the second end of the grounding winding To a tap of 1/3 times the number of turns of one of the adjacent two phase windings to generate a neutral point, wherein the voltage of the ground winding is opposite to that of the phase winding of the phase to which the ground winding belongs. That means the phase difference between the two voltages is 180 degrees.

Compared with the prior art, the neutral point grounding structure and method of the delta-connected winding of the present invention can provide a neutral point so that the voltage differences at the terminals of the three-phase windings are all the same. When the three phases are balanced, any phase line The voltage to the neutral point is the same, so it can solve the shortcomings of the three-phase ground voltage caused by the traditional delta-connected winding grounding method, and can improve the applicable withstand voltage level of the delta-connected winding, so that the delta-connected winding has its own advantages In addition, it also has the advantages of Y-shaped wire winding.

【Description of drawings】

Fig. 1 depicts the wire grounding method of the delta junction wire winding in the prior art;

Fig. 2 illustrates the phase-in-phase grounding method of the delta-connected winding in the prior art;

Fig. 3 shows the schematic diagram of the neutral point grounding structure of the delta-connected winding of the present invention being used for a phase winding;

Fig. 4 shows the actual wiring diagram of the neutral point grounding structure of Fig. 3 used in a phase winding;

Fig. 5 depicts the corresponding vector diagram of Fig. 3;

Fig. 6 depicts a schematic diagram of the neutral point grounding structure of the delta-connected winding of the present invention being used for two-phase windings at the same time;

Fig. 7 is a schematic diagram showing that the neutral point grounding structure of the delta-connected winding of the present invention is simultaneously used for three-phase windings;

Fig. 8 shows the schematic diagram of the neutral point grounding structure of the delta-connected winding of the present invention with six sets of grounding windings;

Fig. 9 depicts the corresponding vector diagram of Fig. 8;

Figure 10 shows a schematic diagram of using a grounded winding group for a phase winding; and

FIG. 11 is a flow chart of the neutral point grounding method for the delta-connected winding of the present invention.

【Detailed ways】

Fig. 3 shows the schematic diagram of the neutral point grounding structure of the delta-connected winding of the present invention used in a phase winding, please refer to Fig. 4 at the same time, Fig. 4 shows the actual wiring of the neutral point grounding structure in Fig. 3 for a phase winding The actual wiring diagram is a wiring diagram of a transformer. Wherein the primary side includes the first phase winding 20 of the primary side, the second phase winding 22 of the primary side and the third phase winding 24 of the primary side, and the _H1 and _H2 connectors of each phase winding can be connected to three phase power supply (not shown). The three-phase windings on the secondary side corresponding to the primary side are the first phase winding 30 , the second phase winding 32 and the third phase winding 34 . The three-phase windings are connected in a delta connection, that is, the _X3 joint of the first phase winding 30 is connected to the X1 joint of the second phase winding 32, and the _X3 joint of the second phase winding ₃₂ is connected to the third phase winding 34. The _X1 connection of the third phase winding 34 is connected to _{the X1} connection of the first phase winding 30 . Each phase winding on the secondary side has N turns respectively. In the neutral point grounding structure of the present invention, at least one of the three-phase windings on the secondary side is selected to add a grounding winding. In this embodiment, a grounding winding 36 is selected to be added to the third phase winding 34. In order to make the illustration clearer, the In the figure, the ground winding 36 and the third phase winding 34 are drawn parallel to each other, which means that the ground winding 36 is added to the third phase winding 34, and the following embodiments will also be represented in this way, and will not be repeated. The ground winding 36 includes a first end and a second end. Among them, the first end is connected to the ground point, that is, the neutral point n, and the second end is connected to the tap of 1/3 times the number of turns of one of the phase windings of the two adjacent phases. The so-called tap is 1/3 of the secondary phase winding. It is generated by drawing an end point at a multiple of turns. In this embodiment, the second end of the ground winding 36 added by the third phase winding 34 is connected to the taps of 1/3N turns of the first phase winding 30, wherein the voltage of the ground winding 36 is related to the voltage of the ground winding 36. The voltage of the phase winding (third phase winding 34 ) of the phase is opposite. Since the ground winding 36 is added to the third phase winding 34 , it means that the phase winding of the phase to which the ground winding 36 belongs is the third phase winding 34 . In this embodiment, when the voltage of the third phase winding 34 is V _ca , the voltage of the ground winding 36 must be V _ac so that the voltages of the phase lines a, b, c to the neutral point n are all the same . The opposite meaning of the above voltage means that the phase difference of the two voltages is 180 degrees.

即相电压为

因此改善了传统三角形结线绕组接地方法导致三相线对地电压不一致的问题。也因相电压从V降低为因此设备的绝缘耐压等级需求降低，代表提高了三角形结线绕组适用的绝缘耐压等级。As shown in Figure 4, the voltage between the lines is V, and the voltages of the phase lines a, b, and c to the neutral point n are consistent as

That is, the phase voltage is

Therefore, the problem of the inconsistency of the three-phase line-to-ground voltage caused by the traditional delta-connected winding grounding method is improved. Also due to the reduction of the phase voltage from V to Therefore, the requirements for the insulation withstand voltage level of the equipment are reduced, which means that the insulation withstand voltage level applicable to the delta junction winding is improved.

FIG. 5 shows a corresponding vector diagram of FIG. 3 . When the three-phase voltage of this grounding structure is balanced, any phase line a, b, c connected to each phase winding has the same voltage to the neutral point n, so it can solve the three-phase ground voltage caused by the traditional delta-connected winding grounding method differences and the resulting problems. In particular, drawing the 1/3V _ac vector and the voltage vector V _ca of the third phase winding 34 parallel to each other means that a ground winding 36 is added to the third phase winding 34 and connected to the first phase At the tap of 1/3 times the number of turns of the winding 30 (that is, at 1/3V _ab ), the vector arrows of 1/3V _ac and V _ca are opposite, which means that the phase difference between the two voltages is 180 degrees.

In order to consider the reliability of grounding, grounding windings can be added above the two-phase windings at the same time. FIG. 6 is a schematic diagram showing that the neutral point grounding structure of the delta-connected winding of the present invention is simultaneously used in two-phase windings. In this embodiment, the third phase winding 34 and the first phase winding 30 are selected to add ground windings 38 and 40 respectively. The first end of the ground winding 38 is connected to the ground point, and the second end is connected to the tap of 1/3 times the number of turns of the first phase winding 30 , that is, 1/3N turns. The first end of the ground winding 40 is connected to the ground point, which is the neutral point n, that is, connected to the first end of the ground winding 38, and the second end of the ground winding 40 is connected to 1 of the second phase winding 32. /3 times the number of turns at the tap. At the same time, grounding windings 38 and 40 are added to the two-phase windings, and the voltage is matched. When the three-phase voltages are balanced, any phase line a, b, c connected to each phase winding has the same voltage to the neutral point n. The collocation of the voltages is illustrated in Figure 3 and will not be repeated here.

FIG. 7 is a schematic diagram showing that the neutral point grounding structure of the delta-connected winding of the present invention is simultaneously used in three-phase windings. In this embodiment, ground windings 42 , 44 and 46 are respectively added to the three-phase windings. The first ends of the three ground windings 42, 44 and 46 are connected to a ground point, the so-called neutral point n. The second end of the ground winding 42 is connected to the tap of 1/3 times the number of turns of the first phase winding 30, the second end of the ground winding 44 is connected to the tap of 1/3 times the number of turns of the second phase winding 32, the ground winding The second end of 46 is connected to the tap of 1/3 times the number of turns of the third phase winding 34 . At the same time, grounding windings 42, 44, and 46 are added to the three-phase windings, and the voltage is matched. When the three-phase voltages are balanced, any phase line a, b, c connected to each phase winding has the same voltage to the neutral point n . The collocation of the voltages is illustrated in Figure 3 and will not be repeated here.

FIG. 8 is a schematic diagram of the neutral point grounding structure of the delta-connected winding of the present invention with six sets of grounding windings. The present invention can have at most 6 groups of grounding windings at the same time, which are marked as 48, 50, 52, 54, 56 and 58 respectively. The connection method of the ground windings 48 , 50 and 52 is the same as that in FIG. 7 , and the first terminals of the three are connected to the ground point at the same time, which is the neutral point n. The second end of the ground winding 48 is connected to the tap of 1/3 times the number of turns of the first phase winding 30, the second end of the ground winding 50 is connected to the tap of 1/3 times the number of turns of the second phase winding 32, the ground winding The second end of 52 is connected to the tap of 1/3 times the number of turns of the third phase winding. It should be noted that the tap position of 1/3 times the number of turns here refers to counting from the end point of X ₁ to the end point of X ₃ (see Figure 4). Similarly, grounding windings 54, 56, and 58 can also be added at 1/3 from the _X3 end point to the _X1 end point, and the first ends of the three are also connected to the neutral point n, while the second end of the grounding winding 54 end is connected to the tap of 1/3 times the number of turns of the first phase winding 30, the second end of the ground winding 56 is connected to the tap of 1/3 times the number of turns of the second phase winding 32, and the second end of the ground winding 58 is connected to To the tap of 1/3 times the number of turns of the third phase winding 34.

It should be noted that, in the embodiment of FIG. 3 , the second end of the ground winding added by the third phase winding 34 can also be connected to the tap of 2/3 times the number of turns of the second phase winding 32 group of another adjacent phase. (ie the ground winding 56), the 2/3 times the number of turns tap is calculated from the _X1 terminal to the _X3 terminal, that is, it represents 1/3 of the calculation from the _X3 terminal to the _X1 terminal. Similarly, when the voltage of the third phase winding 34 is V _ca , the voltage of the ground winding must be V _ac , that is, the phase difference between the two voltages must be 180 degrees.

The grounding windings of the present invention can be grounded from one group to at most six groups at the same time, that is, any one to five of the six groups of grounding in FIG. 8 can be removed, and at least one group of grounding windings can be retained.

Figure 9 shows the corresponding vector diagram of Figure 8. At the same time, six groups of grounding windings are added to the three-phase windings. When the three-phase voltage is balanced, any phase line a, b, c of each phase winding is connected to the neutral point n voltage are the same.

The above-mentioned ground winding in FIG. 3 can also be replaced by a ground winding group. Please refer to FIG. 10 , which shows a schematic diagram of using a ground winding group for a phase winding in the present invention. The phase windings 30, 32, and 34 are connected in the form of a delta connection, and the grounding winding group 70 is formed by parallel connection of two grounding windings 60 and 62 whose turns are 1/3 times the number of turns of the third phase winding 34, including the first end for grounding, and the second end is used to be connected to the tap of 1/3 times the number of turns of one of the adjacent phase windings, in this embodiment it is connected to the tap of 1/3 times the number of turns of the first phase winding 30 , to generate a neutral point n. Of course, it can also be connected to the tap of 2/3 times the number of turns from the X ₁ end to the X ₃ end of the second phase winding, which means 1/3 of the X ₃ end to the X ₁ end, similar to the one in Figure 8 ground winding 56 . The voltage of the ground winding group 70 is opposite to the voltage of the third phase winding 34 of the phase to which the ground winding group 70 belongs. That is, when the voltage of the third phase winding 34 is V _ca , the voltage of the ground winding group 70 must be V _ac , so that the voltages of the phase lines a, b, c connected to each phase winding to the neutral point n are uniform. same. The above meaning that the voltages are opposite means that the phases of the voltages differ by 180 degrees.

The ground winding group can also be implemented in any two phases or three phases of the three-phase windings as shown in Fig. 6 to Fig. 7 . Up to six sets of grounding winding groups can be grounded at the same time, as shown in Figure 8. The grounding winding groups can also be grounded from one group to a maximum of six groups at the same time, that is, any one to five groups of the six groups in FIG. 8 can be removed, and at least one grounding winding group can be retained.

The ground winding group is not limited to the parallel connection of the two ground windings mentioned in this embodiment, and multiple groups of ground windings can also be connected in parallel to achieve a neutral point structure.

When the neutral point n is drawn out and grounded as in the above embodiments, the delta-connected winding is a three-phase four-wire type. It is also possible not to lead out the neutral point n, then the delta junction winding is a three-phase three-wire type.

Fig. 11 shows the flow chart of the neutral point grounding method of the delta-connected winding of the present invention, the delta-connected winding has first, second and third phase windings, and each phase winding has several turns respectively, the method includes Follow these steps:

In step S10, at least one phase winding is selected among the first, second and third phase windings to add a ground winding, and the number of turns of the ground winding is 1/3 times the number of turns of the phase winding;

In step S20, grounding the first end of the grounding winding; and

In step S30, the second end of the ground winding is connected to a tap of 1/3 times the number of turns of one of the adjacent phase windings to generate a neutral point, wherein the voltage of the ground winding is the same as that of the phase winding of the phase to which the ground winding belongs. The voltage is reversed.

The neutral point grounding structure and method of the delta-connected winding of the present invention can be applied to phase windings of double windings or multi-windings.

The main advantages of the present invention include: (a) when the three phases are balanced, any phase line has the same voltage to the neutral point, which improves the problem that the traditional delta-connected winding grounding method causes the voltage inconsistency between the three-phase lines to the ground; (b) increases After grounding the winding, the applicable withstand voltage level of the delta-connected winding is increased, so that the delta-connected winding has its own advantages, and also has the advantages of the Y-shaped connected winding.

Claims (10)

1. A neutral point grounding structure of a delta-connected winding, the delta-connected winding has first, second and third phase windings, and each phase winding has several turns respectively, characterized in that: in the In at least one phase winding of the first, second and third phase windings, a grounding winding whose number of turns is 1/3 times the number of turns of the phase winding is added, wherein the grounding winding includes a first end for grounding, and a second The terminal is used to connect to the tap of 1/3 times the number of turns of one of the adjacent phase windings to generate a neutral point, and the voltage phase of the grounded winding is 180 degrees different from the voltage phase of the phase winding to which the grounded winding belongs. 2. The neutral point grounding structure according to claim 1, wherein the phase windings are double windings or multiple windings. 3. The neutral point grounding structure as claimed in claim 1, wherein the tap is generated by drawing an end point from the phase winding. 4. The neutral point grounding structure as claimed in claim 1, characterized in that: the neutral point is led out by a wire, so that the triangular junction wire winding is formed into a three-phase four-wire type; or the neutral point does not have a wire lead out , so that the triangular knot-wire winding becomes a three-phase three-wire type. 5. A neutral point grounding structure of a delta-connected winding, the delta-connected winding has first, second and third phase windings, and each phase winding has a number of turns respectively, characterized in that: in the A grounding winding group is added to at least one of the first, second and third phase windings, and the grounding winding group is formed by parallel connection of at least two grounding windings whose turns are 1/3 times the number of turns of the phase winding respectively. The ground winding group includes a first terminal for grounding, and a second terminal for connecting to a tap of 1/3 times the number of turns of one of the adjacent phase windings to generate a neutral point, the voltage of the ground winding group The phase is 180 degrees different from the voltage phase of the phase winding of the phase to which the grounded winding group belongs. 6 . The neutral point grounding structure as claimed in claim 5 , wherein the phase winding is double winding or multi-winding, and the tap is generated by leading out an end point from the phase winding. 7 . 7. The neutral point grounding structure as claimed in claim 5, characterized in that: the neutral point is led out by a wire, so that the triangular junction wire winding is formed into a three-phase four-wire type; or the neutral point does not have a wire lead out , so that the triangular knot-wire winding becomes a three-phase three-wire type. 8. A neutral point grounding method for a delta-connected winding, the delta-connected winding has first, second and third phase windings, each phase winding has several turns respectively, it is characterized in that: the method Contains the following steps: In at least one phase winding of the first, second and third phase windings, a grounding winding whose number of turns is 1/3 times the number of turns of the phase winding is added; grounding a first end of the ground winding; and Connecting a second end of the ground winding to a 1/3 times the number of turns tap of one of the adjacent phase windings to create a neutral point, wherein the voltage phase of the ground winding is the same as the phase winding of the phase to which the ground winding belongs The voltage phase difference of 180 degrees. 9 . The neutral point grounding method according to claim 8 , wherein the phase winding is double winding or multi-winding, and the tap is generated by drawing an end point from the phase winding. 10 . 10. The neutral point grounding method according to claim 8, characterized in that: the neutral point is led out by a wire, so that the triangular junction wire winding becomes a three-phase four-wire type; or the neutral point does not have a wire lead out , so that the triangular knot-wire winding becomes a three-phase three-wire type.

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