JPS6346713A - Transformer for two phase/three phase conversion - Google Patents

Abstract

PURPOSE:To miniaturize the title transformer, and to reduce manufacturing cost by generating voltage having the same magnitude and phase difference at 90 deg. at every two pair between respective terminal in a seat A and a seat B on the secondary side when three-phase voltage is applied to the primary side. CONSTITUTION:When a three-phase power supply is applied to primary windings 16U, 16V, 16W, voltage having the same magnitude and phase difference 90 deg. is generated ay every two pair among respective terminal TA-NA1, NA2-NA1, TB-NB1, NB2-FB in a seat A and and a seat B on the secondary side. When the same load is connected to four secondary terminals, balancing three-phase currents are caused to flow through the three-phase power supply. Both the seat A and the seat B are given windings generating voltage E2/2 at every two pair, and two pairs of the windings 17u1 and 17w1, 172 and 17w2 in the seat A and two pairs of the windings 17u3 and 17w3, 17u4 and 17w4 in the seat B are connected respectively in series, and grounded through a discharge device 8 at nodes. Accordingly, the same voltage E2 as conventional devices is acquired among both each terminal of the seat A and the seat B, but an insulating level on the secondary side may by kept at a value corresponding to E2/2, and an auto-transformer can be unnecessitated.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is used in a three-phase power transmission system with a direct grounding of the neutral point, and is particularly directed to a three-phase to two-phase conversion transformer with improved two-phase side. Concerning vessels.

(Prior art) A feeding transformer for supplying power to high-speed electric cars includes a three-phase to two-phase conversion transformer 1 called a modified Woodbridge connection and a step-up transformer as shown in Fig. 12. 2 is used.

The three-phase to two-phase conversion transformer 1 has a primary winding with a star connection and receives power at a three-phase voltage E1, and a secondary winding with a double triangular connection in which V-phases are connected in parallel.

If the voltage between one set of output terminals ac of this secondary winding is E2, the voltage between the other set of output terminals bd is E, /JN
Therefore, the phase difference between the voltages between terminals ac and terminals b'd is 9
It is 0 degrees.

Step-up transformer 2 has voltage E2//3 between input terminals b'd'
This is an autotransformer that boosts the voltage and generates voltage E2 between output terminals bd.

In this modified Woodbridge connection transformer system.

Since the primary neutral point 0 can be directly grounded, power can be directly received from the ultra-high voltage power transmission system, and there is an advantage that the insulation of the primary winding can be significantly reduced. However, since a step-up transformer 2 is required in addition to the three-phase to two-phase conversion transformer 1, it is larger, the manufacturing price is higher, and the disadvantage is that it requires a large grounding area and a large amount of construction cost. There is.

Next, the reduction of the insulation class on the secondary side will be explained.

Figure 13 shows a power supply 4 connected to the primary side of a single-phase secondary winding heavy duty transformer 3, which is equivalent to a single seated transformer of the modified Woodbridge connection transformer system, and a breaker 5 connected to the secondary side. connect the autotransformers 6A, 6B, and 6C, and connect the autotransformers 6A, 6B, and
The neutral point of 6C is connected to the rail 7 and grounded via the discharger 8, indicating a conventional autotransformer power system (AT system) for supplying power to the electric car 9. In this system, the secondary side of the heavy duty transformer 3 is non-grounded, so when the autotransformers 6A, 6B, and 6C are not connected, that is, when the breaker 5 is open, the secondary side is grounded. In consideration of the occurrence of short circuits, the insulation class is set to correspond to the secondary voltage E2, which is twice the electric vehicle voltage ET.

Fig. 14 shows a recently developed new AT system, in which the heavy duty transformer 10 is a single-phase three-winding type having two sets of secondary windings with a voltage E2/2 equal to the electric vehicle voltage E7. The autotransformer 6A, which is a linear transformer and is the first AT in the substation, is omitted. That is, the primary winding]
1 is connected to a power source 4 with a voltage E1, and a secondary winding 12T,
12F neutral point side terminal N1. Series capacitor 13 to N2
are connected in series, a protective gap 14 is connected in parallel to the series capacitor 13, and the connection point N is connected to the rail 7 and grounded via the discharger 8, and the line side terminal T
, F are connected to autotransformers 6B and 6G via a breaker 5 to supply power to an electric vehicle 9. FIG.

Although the series capacitor 13 and the protective gap 14 are not necessarily necessary devices, the purpose of installing the series capacitor 13 is to compensate for the leakage reactance of the transformer winding, reduce the voltage fluctuation on the secondary side, and reduce the voltage fluctuation of the electric vehicle 9. This is to improve the operating characteristics, and the protective gap 14 prevents overcurrent such as short circuit current from occurring in the secondary winding 12T.

When the current starts to flow to 12F, the same current also flows to the series capacitor 13, and the voltage e0 at both terminals rises. When it exceeds a certain value, the gap is discharged and the series capacitor 13 is short-circuited. When the series capacitor 13 is short-circuited by the protective gap 14, the magnitude of overcurrent such as short-circuit current can be limited to a value determined by the impedance of the power supply and the transformer, so that the strength of short-circuits in the transformer winding etc. is not a problem. It has become.

In actual use, these circuits are prepared for both sides, configured so that the phase difference between their output voltages is 90 degrees, and if the loads on both sides are the same, the power from the three-phase power supply on the primary side is The current is such that three-phase balance is obtained. In this new AT system, even when the breaker 5 is open, the connection point N is connected to the rail 7 and grounded via the discharger 8, so the insulation class on the secondary side is equal to the electric car voltage ET. That is, a value corresponding to the voltage E2/2 of one side of the secondary winding may be sufficient, which can be half of that of the conventional system. Moreover, since the secondary winding is a single-turn connection connected at the connection point N, the first AT
Since it also has the function of the autotransformer 6A, the autotransformer 6A can be made unnecessary as shown in FIG.

(Problems to be Solved by the Invention) In a modified Woodbridge connection three-phase to two-phase conversion transformer as shown in FIG. Therefore, it cannot be applied to the new AT system, and the insulation class on the secondary side must be determined by the secondary voltage E2. Furthermore, an autotransformer 6A is required, which increases the size and manufacturing cost.

An object of the present invention is to provide a three-phase to two-phase conversion transformer that is compact and can be manufactured at a reduced manufacturing cost as a heavy-duty transformer employed in the new AT system described above.

[Structure of the invention]

(Means for Solving the Problems) The three-phase to two-phase conversion transformer according to the present invention has a primary winding connected in a star shape, and a secondary winding connected to the first phase with the number of turns N/6. The third phase winding was connected in a dogleg shape so that the phase difference was 60 degrees, and the second phase winding with the number of turns N/3 was connected so that the phase difference was 120 degrees. Prepare two sets of wires, use both ends as the secondary terminals of the B seat, and separate the first and third phase windings with the number of turns N / (2JT) so that the phase difference is 120 degrees. Prepare two sets connected in the shape of a diagonal.

Both ends have two terminals at the A position, and the tertiary winding is triangularly connected.

When a three-phase power supply is applied to the primary winding, two sets of voltages with the same magnitude and a phase difference of 90 degrees are generated between each terminal of the A and B terminals on the secondary side. When the same load is connected to the three-phase power supply, balanced three-phase current flows through the three-phase power supply.

(Function) Two sets of windings that generate a voltage Ez/2 are provided for both the A seat and the B seat, and the two sets of windings on the A seat and the two sets of windings on the B seat are connected in series, respectively. By grounding through the discharger at the connection point, the same voltage E2 as before can be obtained between the terminals of A and B, but the insulation class on the secondary side is E2/2.
A value equivalent to is fine. Further, since both of the secondary windings have a single-turn connection and also have the function of the first AT's auto-transformer, the need for an auto-transformer can be eliminated.

(Example) The present invention will be described below with reference to an embodiment shown in FIG.

The three-phase to two-phase conversion transformer 15 of this embodiment has U, V, and W phase primary windings 16U, 16V, and 16Wt! : Consists of a primary winding with a normal star-shaped connection, whose neutral point O can be grounded, and a secondary winding with a special connection described later.
These windings are wound on one or more iron cores (not shown).

The secondary windings are two windings each with the number of turns of the first phase (U phase) and third phase (W phase) being N/(24IT) 17u1.17
u2゜17w, , 17w, and two 17v3.17 windings with the second phase (V phase) having the number of turns N/3. and two windings 17u each with the first phase (U phase) and third phase (W phase) having a number of turns of N/6.

17u4.17w, , 17w, and 17u1, 17w1.17u, and 17shi2 as shown in Figure 1.
Connect them to each other in the shape of a letter A, and connect them to the secondary terminals TA-NA□,
NA□-FA, 17u and 17 connected in a dogleg shape
w1.17u4 and 17w4 and 17v each, and 17
v4 is connected to the secondary terminal TR-NB1. NB2-F
, and so on.

In the above-mentioned square-shaped connection, since the phase difference between one winding 17u and 17v or 17u2 and 17su2 is 120 degrees, the secondary terminals T^-NA and NA□-FA of A position are connected. The voltage generated between them has a value corresponding to the number of turns N/2.

On the other hand, the dogleg-shaped connection described above has two windings 17u3 and 1
7v or 17u4 and 17v4 are connected so that the phase difference is 60 degrees, so the B-located secondary terminal TB-N,
□.

The voltage generated between N B Z F 3 is N/6 + by adding the voltage generated by the second phase winding 17v3.17v4.
N/3 = the value corresponding to the number of turns of N/2, the magnitude is the same as the voltage generated between the secondary terminals of the A position, and the phase is 90
This means that they are off by a degree (orthogonal).

Next, if the configuration is as in this embodiment, A on the secondary side.

It will be explained that when the same single-phase load is balanced on both B seats, the primary side three-phase power supply becomes a three-phase balanced load.

First, in order to simplify the analysis of the current flowing through each part, the number of turns of each winding is set as shown in FIG. /4317v4 is set to 100, the line spacing on the primary side corresponds to 1, and the secondary side has terminals T^-FA+ TB connected in series on both A and B.
Each FB corresponds to 1.

In Figures 3 to 5, a three-phase power supply 19 is connected to the primary side, and A
This is the current distribution when the load 20 is placed only at the seat, and the current flowing through the load 20 is assumed to be 1. In FIG. 3, there is a load between the secondary terminals TA and NA1, and the secondary windings 17u1.
It is assumed that 1 of the secondary side load current flows through 17W, and the above primary current flows through each phase of 160W and 16W of the primary winding, but this relationship is It is determined from the condition that the ampere turns of each phase match in three phases.

In Fig. 4, when there is a load 20 between the secondary terminals NA and -FA, the relationship is the same as in Fig. 3, but what is important here is that this transformer under the conditions shown in Figs. They must be designed so that their leakage impedances are almost the same.

Figure 5 shows a case where both the conditions in Figures 3 and 4 are superimposed, and since the currents of the primary windings 16U and 16W are in phase, it is calculated as the sum of the currents, and the current IUA of the primary winding 1160 is The current 11+1A of the primary winding 16W is the same and is 1. 1
No current flows through the secondary winding 16V, and the secondary winding 17u1.1
The current flowing through 7w1 and 17112 + 17w is 1.

Figures 6 to 8 show the current distribution when the load 20 is applied only to the B position, but since the voltage generated at the B position is delayed by 90 degrees in phase with respect to the voltage generated at the A position, the current flowing also There is a phase difference of 90 degrees, which is indicated by adding -j. Also,
The subscript of each code and symbol is also displayed with B added instead of A.

In Figure 6, a load of 2o is placed between the secondary terminal 'r and N81.
, and a load current of −j1 flows through the load 20. This load current is connected in series with the winding 17u.

17V, , flows to 17w3. The primary winding cancels the ampere turn due to the load current of the secondary winding. In Figure 7, there is a load 20 between the secondary terminals NB2 and FB, and the relationship is similar to that in Figure 6. However, the important thing here is to make the leakage impedance of this transformer almost the same under the conditions shown in FIGS. 6 and 7, as in the case of the A seat.

Figure 8 shows a case where both the conditions in Figures 6 and 7 are superimposed, and the primary winding 16U, 1.6V, 16W (7) each current is in phase, so it is found by the calculated sum, and the primary The values of the current IU8 of the winding 16U and the current IWB of the primary winding 16W are current 1□B
becomes -j1.

Figure 9 shows the current distribution in each part when the same load 2o is connected to the A and B locations at the same time and is applied to the new AT method shown in Figure 14.The positive direction of each current is indicated by an arrow. It is displayed as .

This figure 9 shows the case where both the conditions of figure 5 and figure 8 are superimposed, so there is a 90 degree phase difference in the current in the primary winding.
It is determined by vector sum, and the vector diagram is shown in Figure 1O.

That is, the first phase current iu of the primary winding 16U is IUA
At IUB, the second phase current Iv of one large turn IjA16v
is IVA+IVB, and the third phase current iw of the primary winding 16W is calculated as -1sA IWB, respectively.

Therefore, as can be seen from Figures 9 and 10, A on the secondary side
When the same load is applied to the seat and B seat at the same time, the phase is 1 for each
It can be seen that the three phases are balanced by 20 degrees.

Also. When using the primary side with the neutral point grounded, the 5th
When a load is applied only to the A position in the figure, when a load is applied only to the B position in Figure 8, or when a load is applied to both A and B positions in Figure 9, the current flowing through each part is the primary of each phase. Since it is determined only by the coincidence of ampere turns between the winding and the secondary winding, the zero-sequence current flowing to the neutral point O can be made zero without any particular restriction on impedance between each winding. As a result, as in the conventional case, the primary neutral point O can be directly grounded and used, power can be directly received from the ultra-high voltage power transmission system, and the insulation of the primary winding can be significantly reduced.

Since the wiring of the present invention does not have a closed circuit connection in the primary and secondary windings, a stable triangular wiring is used to circulate the third harmonic component contained in the exciting current. Winding 1
8 is required. The stabilizing winding 18 also has the function of lowering the zero-sequence impedance, which is no different from the function of the stabilizing winding of a normal three-phase transformer. Further, if necessary, it is also possible to use the stabilizing winding 18 as a tertiary winding, connect a capacitor for power factor improvement, or take on an internal load.

Next, consider the utilization rate of the winding. From FIG. 2 and FIG. 9, the primary winding 16U, 16V, 16W (7) capacity is the sum of three. APJ, secondary winding 17u, + 17u2.17t
i0.17w2 B position secondary winding 17u3v 17u4
The two-phase winding capacity of t 17w3.17w4 is 0.667
(=ChoXlX4), secondary winding of B seat 17V, , 1
The two-phase winding capacity of 7v4 is 0.667 (=.

XlX2), the total capacity of the secondary winding is 2.488.

Therefore, if the total secondary load is 100%, the winding capacity is 100% for the primary winding and 124.4% for the secondary winding, and the equivalent capacity is 112.2%. Tertiary winding 18
When using as a stabilizing winding, this should be taken into account as the transformer's effective equivalent capacity, but the capacity of the stabilizing winding is determined by other factors, and it does not take a load. Since it is generally sufficiently small compared to the primary side capacity of the transformer, it is ignored here. Also, the tertiary winding 1
When 8 takes on a load for the purpose of in-house power supply, etc., the tertiary winding needs to have the capacity required for that purpose, but in this case, even with the conventional method, a larger capacity is required. Since this is necessary, only the equivalent capacitance of the primary and secondary windings will be compared here.

In the conventional modified Woodbridge connection transformer shown in FIG. Since the equivalent capacity of the transformers is 21.1% (=buuni"-mu5L and 3"-), the total equivalent capacity of both transformers is 121.2%. Therefore, the transformer 15 of this embodiment requires an equivalent capacity of 92.7%. Further, since there is no need to separately provide the step-up transformer 2, the ethane system can be made smaller and lighter, and its installation area can be reduced.

Regarding the insulation class of the secondary winding, check its neutral point side terminal NA□, NA2. Since NB, N82 is always connected to the rail 7 through the series capacitor 3 and grounded through the discharger 8, it is clear that the insulation class corresponding to half the conventional secondary voltage is sufficient, and the secondary circuit It is possible to reduce the insulation class of circuit breakers, disconnectors, lightning arresters, etc. used in

FIG. 11 shows a modification of the secondary winding. A-1~A-
4 shows an example of the secondary winding at A position, and B-1 to B-12 show B
An example of the secondary winding of the seat is shown, and the same electrical characteristics and effects as the embodiments of the present invention described above can be obtained by any combination of one set of winding of the A seat and one set of the winding of the B seat. be able to. In this case, the primary and tertiary windings are the same as described above.

[Effects of the Invention] As explained above, according to the present invention, the primary winding is star-shaped and its neutral point can be directly grounded, making it possible to receive power directly from the ultra-high voltage power transmission system. , the primary winding can be stage-insulated or reduced-insulated, and one end of the secondary winding can be grounded, so it can be applied to new AT system circuits, the insulation class on the secondary side can be halved, and special It is possible to provide a three-phase to two-phase conversion transformer that does not require a step-up transformer.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram showing one embodiment of a three-phase to two-phase conversion transformer according to the present invention, Fig. 2 is an explanatory diagram showing the turn ratio of each winding in the transformer shown in Fig. 1, and Fig. 3 Figure 5 is from Figure 1.
Figures 6 to 8 are explanatory diagrams showing the current distribution when a load is applied only to the A seat in the transformer shown in Figure 1. Figure 9 is an explanatory diagram showing the current distribution when the same load is applied to both A and B in the transformer shown in Figure 1. 9 is a current vector diagram, FIG. 11 is a connection diagram showing a modified example of the secondary winding of the present invention, FIG. 12 is a connection diagram of a conventional modified Woodbridge connection feeding transformer, and FIG. 13 14 is a circuit diagram of an AT system using a conventional modified Woodbridge connection, and FIG. 14 is a circuit diagram of a new AT system using a new three-phase to two-phase conversion transformer. 1.2... Modified Woodbridge connection three-phase two-phase conversion transformer, step-up transformer 3.10... Feeding transformer 4... Single-phase power supply 5.
... Breaker 6A, 6B, 6C ... Autotransformer 7.
...Rail 8...Discharger 9...Electric car
11, 16U, 16V, 16W...Primary winding 12T.
...Secondary winding 12F connected to the contact wire side...Secondary winding 13 connected to the feeder side...Series capacitor 14...Protection gap 15...Three-phase two-phase according to the present invention Conversion transformer 17u, , 17uz, 17u,
, 17LI4.17v1, 17V2.17V3.17V
4. Figure 1 Figure 3 Figure 7 Figure 9 Figure 10 Figure 11 Figure 12 Procedure correction mouth (voluntary) Showa year month day 6L12. -2

Claims (1)

[Claims] The primary winding is star-shaped with the same number of turns for all three phases.
For the secondary winding, prepare two windings with the number of turns of N/3 for the second phase and two windings each of the number of turns of N/6 for the first and third phases. The windings of the first phase, second phase, and third phase are Prepare two sets of windings of each phase connected in series, and two sets of windings each with the number of turns N/(2√3) for the first and third phases. It consists of two sets in which one winding and one 3rd phase winding are connected in series so that the phase difference is 120 degrees, and the tertiary winding is a triangular connection in which the number of turns is the same for all three phases. In a transformer for three-phase to two-phase conversion having a group of windings, both ends of the first and third phase windings of the secondary winding connected in series are used as the secondary terminals of the A position, and the When the windings of the 1st, 2nd, and 3rd phases are connected in series, both ends are the secondary terminals of the B position, and when a three-phase voltage is applied to the primary side, the secondary side A and B A transformer for three-phase to two-phase conversion, characterized in that two sets of voltages having the same magnitude and a phase position of 90 degrees are generated between each terminal of the position.