JPH0569287B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a stable winding type three-phase to two-phase conversion transformer that is used in a three-phase power transmission system with a directly grounded neutral point, and in particular has an improved two-phase side. [Technical background of the invention and its problems] A three-phase to two-phase conversion transformer 1 called a modified Utsudo bridge connection as shown in Fig. 13 is used as a feeding transformer for supplying power to high-speed electric cars. and a step-up transformer 2 are used. In the three-phase to two-phase conversion transformer 1, the primary winding has a star connection and receives power at a voltage _E1 , and the secondary winding has a double triangular connection in which V-phases are connected in parallel. The voltage between one set of output terminals ac of this secondary winding is
If E ₂ , the voltage between the other set of output terminals b′d′ is
E ₂ /√3, and the phase difference between the voltages between terminals ac and terminals b'd' is 90 degrees. Step-up transformer 2 has a voltage between input terminals b′d′ E ₂ /√
This is an autotransformer that boosts E 3 and generates voltage E ₂ between output terminals b and d. In this modified Utsudo bridge connection transformer system,
Since the primary side neutral point 0 can be directly grounded, there is an advantage that power can be directly received from the ultra-high voltage power transmission system, and 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, there are disadvantages in that the size is large, the manufacturing cost is high, and a large installation space and large construction costs are required. Next, the reduction of the insulation class on the secondary side will be explained. Fig. 14 shows a power supply 4 connected to the primary side of a single-phase two-winding feeding transformer 3, which is equivalent to a single seat of a modified Utsudo bridge-connected transformer, and a power supply 4 connected to the secondary side via a shear breaker 5. A conventional autotransformer feeding system (AT system) is shown in which autotransformers 6A, 6B, and 6C are connected to supply power to an electric car 7. In this system, the secondary side of the feeding transformer 3 is non-grounded, so when the autotransformers 6A, 6B, and 6C are not connected, that is, when the shield breaker 5 is open, Considering that a ground fault may occur on the secondary side, the electric vehicle voltage
The insulation class corresponds to the secondary voltage _E2 , which is twice E _T. Figure 15 shows a recently developed new AT system, in which the feeding transformer 8 is connected to the electric vehicle voltage.
It is a single-phase three-winding transformer with two sets of secondary windings with E ₂ /2 equal to _T , and the first (substation)
The autotransformer 6, which is an AT, is omitted. That is, the power source 4 of voltage E ₁ is connected to the primary winding 9, the secondary windings 10T and 10F are connected in series, and the connection point N is connected to the rail 21 and grounded via the discharger 22. and the terminals T at both ends,
F, autotransformers 6B and 6C are connected to F via a disconnector 5.
2 is a circuit diagram for connecting the electric vehicle 7 and supplying power to the electric vehicle 7. FIG. 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 shield breaker 5 is open, the connection point N is connected to the rail and grounded via the discharger, so the insulation class on the secondary side is equal to the electric car voltage E _T , That is, a value corresponding to the voltage E ₂ /2 of one side of the secondary winding is sufficient, which can be half of that of the conventional system. Moreover, since the secondary winding is an auto-winding connection that is grounded at the connection point N, it also has the function of the auto-transformer 6A called 1st AT, so the auto-transformer 6A as shown in FIG. It can also be made unnecessary. [Object of the Invention] The object of the present invention is to provide a feeder 9 transformer to be adopted in the new AT system as explained above, and to provide a stable winding type three-phase to two-phase conversion transformer that is compact and can reduce manufacturing costs. It is about providing. [Summary of the Invention] The feeding transformer according to the present invention has its primary winding connected in a star shape, and can be used with its neutral point grounded.
The secondary winding has a number of turns of the second phase coil.
The number of windings is smaller than that of the phase and third phase coils, two star-shaped wires are formed that share the second phase, and the neutral point N is taken out from the middle of the second phase so that it can be grounded. The secondary winding is triangularly connected to pass the circulating current that flows to cancel out unbalanced ampere turns due to the secondary load current, and also serves as a stabilizing winding, which is required in the case of only star-shaped connections. [Embodiments of the Invention] The present invention will be described below with reference to an embodiment shown in FIG. In the transformer 11 of this embodiment, as shown in FIG. The winding 14 is a normal triangular connection with one terminal a grounded, and these windings are wound around an iron core (not shown), forming a type of three-winding transformer. The secondary winding is the first phase (U phase) and the third phase (W
2 coils each (13u ₁ ,
13u ₂ , 13w ₁ , 13w ₂ ) and the second phase (V phase)
It consists of two coils (13v ₁ , 13v ₂ ) with the number of turns (√3-1)N/2, and the second phase coils 13v ₁ , 13v ₂ are connected in series, and the connection point is connected to the neutral 1 of the first phase coil is connected to the lower terminal θ ₁ of the point N.
3u ₁ and 13w ₁ of the third phase coil, and connect 13u ₂ of the first phase coil and 13w of the third phase coil to its upper terminal θ ₂ .
w ₂ is connected to the second phase coils 13v ₁ and 13v ₂ so that the phase difference is 120 degrees, and the remaining terminals are designated as secondary terminals T _A , F _A , T _B , and F _B . As mentioned above, when the number of turns of each coil of the secondary winding is determined and the wires are connected, for example, a triangle is formed in Fig. 1.
For T _A , θ ₁ , and N, the lengths of the two sides (TA − _{θ 1} and θ ₁ and N) are known, and the included angle (TA ₋ θ ₁ − N) is 120 degrees, so the angle θ ₁ − N-T _A is 45 degrees, and terminals T _A , N,
The dotted line 15A connecting F _A is a straight line, and this is called the induced voltage at the A position. Similarly, the dotted line 15B connecting the terminals T _B , N, and F _B is also a straight line, and this is called the induced voltage at the B position. The induced voltage 15A at the A location and the induced voltage 15B at the B location are orthogonal to each other, and the length of the dotted line between the secondary terminal, for example, T _A and the neutral point N, is half the magnitude of the induced voltage 15A. is the number of turns

Corresponds to [formula]. Therefore, if the magnitude of the induced voltage is E ₂ /2 between T _A and N, then between T _A and θ ₁ is

[Formula] The distance between θ ₁ and N is E ₂ /2×√3−1/√6. The relationships between the other secondary terminals F _A , T _B , F _B and the neutral point N are exactly the same as the relationship between the secondary terminal T _A and the neutral point N. An example of the winding arrangement configuration of this transformer 11 is shown in FIG. That is, the tertiary winding 14 is wound around the core leg 16 on the inside and outside of the primary winding 12, and the first group of secondary windings 13u ₁ , 13v ₁ , 13w ₁ is further placed on the innermost side.
Then, on the outermost side, two groups of secondary windings 13u ₂ , 13v ₂ ,
_13w2 is wound on each side, which is called a sanderch arrangement, and the first and third phases have exactly the same configuration, but the second phase has coil 1 of the secondary winding.
Compared to other phases, the number of turns of 3v ₁ and 13v ₂ is (√3
-1)/2 times, and as will be described later, the conduction current is as large as √2 times, so its configuration is different from other phases. In Figure 1, the three-phase voltage is applied to the primary terminal UVW.
If E ₁ is applied, the induced voltage on the secondary side is T _A at A
-N-F _A single phase voltage of 15A and B location T _B -N-
A single-phase voltage 15B of F _B is obtained, and the single-phase voltages 15A and 15B of both sides have the same magnitude E ₂ ,
They have a phase difference of 90 degrees, and if they are configured so that their centers meet at the neutral point N and can be grounded, the voltage to ground of the secondary terminal will be E ₂ /2
Therefore, it can be applied to the circuit of the new AT method shown in Fig. 15. Next, with the configuration as in this embodiment, when the single-phase load is balanced on both A and B on the secondary side, 1
It will be explained that there is a three-phase balanced load for the next three-phase power supply. First, in order to simplify _the analysis of the current flowing through each part, the number of turns of each winding is set to the ratio shown in _FIG .
3w ₁ , 13w ₂

〔Effect of the invention〕

As explained above, according to the present invention, since the temporary side winding is star-shaped, the neutral point can be drawn out and directly grounded, so that it is possible to directly receive power even from an ultra-high voltage line with a large short circuit capacity. Also, the primary winding can be provided with stepped insulation or reduced insulation. And the secondary winding is
Since the neutral point can be extracted and grounded, it can be applied to new AT system circuits, and the insulation class on the secondary side can be halved. Moreover, since a special step-up transformer is not required, the structure is simple, compact and lightweight, reducing manufacturing costs, and the stable winding type three-phase to two-phase conversion transformer requires less installation space. can be provided.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram showing an embodiment of a stable winding type three-phase to two-phase conversion transformer according to the present invention, and Fig. 2 is a schematic configuration showing an example of the winding arrangement of the transformer shown in Fig. 1. Figure 3 is an explanatory diagram showing the turns ratio of each winding in the transformer shown in Figure 1, and Figures 4 to 6 are diagrams showing the transformer shown in Figure 1 with a load applied only to the A seat. Figure 7 is an explanatory diagram showing the current distribution when the transformer shown in Figure 1 is loaded only at the B seat. Figure 8 is an explanatory diagram showing the current distribution when the transformer shown in Figure 1 is loaded. An explanatory diagram showing the current distribution and the positive direction of each current when the same load is applied to the A and B locations at the same time, FIG. 9 is a vector diagram of the current in FIG. 8, and FIG. 10 is an illustration of another example of the present invention. A wiring diagram showing the secondary winding of the embodiment, Fig. 11 is a circuit diagram of an AT system to which the transformer of Fig. 10 is applied, and Fig. 12 shows the secondary winding and reactance of another embodiment of the present invention. An explanatory diagram showing the connection of a compensation series capacitor and a protective gap, Fig. 13 is a wiring diagram of a feeding transformer with a conventional modified Udo bridge connection, and Fig. 14 is a circuit configuration diagram of an AT method with a conventional modified Udo bridge connection. Figure 15 is a circuit diagram of an AT system using a new three-phase to two-phase conversion transformer. 1...Three-phase two-phase conversion transformer with modified mud bridge connection, 2...Step-up transformer with modified mud bridge connection, 3, 8...Feeding transformer, 5...Shield breaker, 6A, 6B , 6C...autotransformer, 7...
Electric car, 10T...Secondary winding connected to the contact wire side, 10F...Secondary winding connected to the feeder side, 11...Stable winding type three-phase to two-phase conversion transformer, 12... ...Primary winding, 13u ₁ , 13u ₂ , 13
v ₁ , 13v ₂ , 13w ₁ , 13w ₂ , 13v ₁₁ , 13
v ₁₂ , 13v ₂₁ , 13v ₂₂ ...each coil of the secondary winding,
14...Tertiary winding, 15A, 15B...A seat, B
Induced voltage at the seat, 16... Iron core leg, 17... Three-phase power supply, 18... Secondary side single-phase load, 19... Series capacitor, 20... Protective gap, 21... Rail, 22... Discharger .

Claims (1)

[Claims] 1. The primary winding has a star-shaped connection in which the number of turns is the same for all three phases, and the secondary winding has two coils each with the number of turns N for the first and third phases, The number of turns of the second phase (√
3-1) one coil of N, and one end of the first phase and third phase coils is connected to both ends of the second phase coil, and one end of the first phase coil and the third phase coil are connected to each other with a phase difference from the second phase.
120 degrees, the other end is used as a secondary terminal, two secondary side induced voltages of the same magnitude are connected so that their phase difference is 90 degrees, and the second A stable winding type three-phase to two-phase conversion transformer, characterized in that the neutral point lead is taken out from the middle of the phase coil, and the tertiary winding is a triangular connection with the same number of turns for all three phases. 2 The secondary winding has the number of turns of the first and third phases N.
and four coils each having a second phase with a number of turns (√3-1)N/2.
Each phase coil is connected in series so that the phase difference is 120 degrees, and both ends are used as secondary terminals, and the four secondary side induced voltages are the same size.
A stable winding type three-phase to two-phase conversion transformer according to claim 1, characterized in that these are connected so that their phase differences are 90 degrees.