CN201081805Y - V-V type compact power transformer for electric traction - Google Patents

Abstract

A power transformer (100) for electric traction comprises a box body (3) and a single magnetic core (10) positioned inside the box body (3), wherein, the single magnetic core comprises a central branch circuit (11) and two collateral branch circuits (12 and 13). A first phase (20) comprises a primary side winding (22) and a secondary side winding (21) which are wound on one branch circuit; a second phase (30) comprises a primary side winding (32) and a secondary side winding (31) which are wound on the other branch circuit.

Description

V-V Compact Power Transformer for Electric Traction

technical field

The utility model relates to a compact power transformer used for electric traction. More specifically, the present invention relates to a V-V connection type compact power transformer, which is especially suitable for electrified railway traction systems. These systems are described below by reference to them, without intending to limit their possible applications in any way.

Background technique

Voltage and current conversion equipment is well known and used in the power industry to deliver power from a generator unit to a load or end user.

Transferring power in an efficient manner requires high voltage levels in order to reduce the current flowing through the lines and thus minimize power losses associated with energy transfer. Therefore, this power transfer is more efficient at high voltages, however, consumers require lower voltage levels such as medium voltage networks due to safety reasons. Electric machines are therefore needed to efficiently convert high voltage power into medium or low voltage power, such machines are known as transformers.

In electric traction applications, especially in railway traction systems, a single-phase AC power system is often required, whereas AC transmission systems are almost always three-phase.

There are different technical options for three-phase input power voltage and single-phase output voltage transformers, depending on the connection of the windings associated with the two voltage systems involved.

In most cases, the so-called V-V connection system has been used in these types of applications in the past to good effect. More specifically, the purpose of using V-V link transformers for traction is to provide medium voltage power (in single phase mode) to railway equipment, which is taken from the three phase high voltage power lines. In its typical design, this type of connection uses two separate and distinct single-phase power transformers with winding connections as follows:

The terminals of the primary winding of each single-phase transformer are connected to two phases of the three-phase power system. Therefore, one of the respective terminals of the two windings will be connected to a common phase, while the other terminal is connected to a different phase;

The secondary windings of each single-phase transformer are connected in series, and the junction of the two windings is normally grounded. Therefore, there is a single-phase AC voltage between the other terminals of these two secondary windings for supplying power to the railway equipment.

The V-V connection provides single-phase power from a three-phase power network, causing only slight imbalances in the three-phase power network. It is also common for one or both windings to include taps to adjust the output voltage. Finally, it is worth reminding that due to the operating conditions of railway equipment, the design of traction transformers has to take into account more severe working conditions than usual power transformers, because traction transformers have to withstand strong, short-term overloads and caused by frequent current surges. high electrodynamic stress on the windings etc.

Although currently used power transformers provide a good solution, they still have certain disadvantages that deserve improvement. In particular, one major disadvantage of the known solution is that it uses two separate single-phase transformers and therefore two separate electromagnetic circuits. Accordingly, these two circuits must be included in two different sealed boxes or in a single sealed box. In both cases, the end result is a bulky solution, especially in terms of size and weight. This directly leads to other disadvantages due to transportation and installation problems and costs, as well as potential maintenance and reliability problems due to the use of twice as many components.

Utility model content

Therefore, the main purpose of the present invention is to provide a new power transformer for electric traction, which overcomes the above-mentioned drawbacks and which, in particular, is more compact, reliable and cheaper than the solutions of the prior art.

This and other objects which will become apparent hereinafter are achieved by a power transformer for electric traction, characterized in that it comprises:

box;

a single magnetic core, which is located inside the box and includes three legs, one of which is located in the center and two legs are located on both sides of the central leg;

a first phase comprising a primary winding and a secondary winding, said winding being wound on one of said three branches;

A second phase comprising a primary winding and a secondary winding, the winding being wound on the other of the three branches.

In a particularly preferred embodiment, the primary and secondary windings of the first phase are wound on the first side branch, and the primary and secondary windings of the second phase are wound on the second side branch.

Description of drawings

Still further features and advantages will become apparent from the description of some preferred but not exclusive embodiments according to the invention, which are illustrated by way of non-limiting example only with the accompanying drawings, in which:

Fig. 1 schematically shows the layout of windings and electromagnetic circuits of a power transformer according to the present invention;

Figure 2 shows a side view of the compact transformer shown in Figure 1 of the V-V connection type ready to be connected to a power system;

Figure 3 illustrates the power transformer of Figure 2 viewed from the rear;

Figure 4 is a top view of the power transformer of Figures 2 and 3;

Figure 5 schematically shows a wiring diagram of the power transformer connections.

Detailed ways

In the following description, the same reference numerals will be used to designate the same or equivalent parts in different drawings.

With reference to the figures cited above, the power transformer for electric traction according to the present invention is fully represented in Figures 2-4 by reference numeral 100, and it comprises: a box 3 containing the working parts of the transformer, such as electromagnetic circuits, windings And its connection, and according to customer requirements, on-load or off-load tap changer. Said box 3 may also include the parts necessary to move the transformer, such as wheels and corbels to transport and lift it, and to place it in its final position. An oil storage and preservation tank 5 is also provided, generally indicated as an oil conservator, to contain the necessary oil to compensate for any changes in the volume of oil contained within the main tank 3, which changes may be caused, for example, by changes in temperature And cause. In Fig. 3 there is also shown a cooling component 6 which is necessary to keep the oil temperature within acceptable levels and to dissipate any internal power dissipation of the transformer. In the illustrated embodiment, the cooling device 6 consists of a radiator and an electric fan. In Fig. 3 there is also illustrated an off-load tap changer wheel 7 and a control cabinet 8 from which the user of the machine can connect to the transformer protection and control equipment. On-load tap changers are also available.

Advantageously, in the power transformer 100 according to the invention, the electromagnetic circuit comprises a single magnetic core, located inside the box 3 , indicated by reference numeral 10 in FIG. 1 . As shown, a single magnetic core 10 includes three branches or branches 11 , 12 , 13 , of which one branch 11 is placed in the center and two branches 12 , 13 are placed on either side of the central branch 11 . The branches 11 , 12 , 13 are connected to each other by a yoke 14 . The first phase 20 comprises a primary winding 22 , eg a high voltage winding, and a secondary winding 21 , eg a medium voltage winding, both wound on one of the three branches 11 or 12 or 13 . The second phase 30 comprises a primary winding 32 , eg a high voltage winding, and a secondary winding 31 , eg a medium voltage winding, both wound on the other branch 11 or 12 or 13 .

As defined by international standards and practices, the definition of high voltage here means a voltage level above 1kV, while the definition of medium voltage is usually used to indicate such a high voltage range, that is, above 1kV, up to 72kV or even up to 100kV subrange of voltage levels.

According to the preferred embodiment shown in Fig. 1, the primary winding 22 and the secondary winding 21 of the first phase 20 are wound on the first side branch, such as the side branch 12; and the primary winding 32 and the secondary winding 32 of the second phase 30 The side winding 31 is wound on the second side branch 13 . The central branch 11 constitutes a return path for the magnetic flux circulating through the side branches 12 , 13 . In other words, in operation, in one side branch 12 of the transformer, a magnetic flux corresponding to the phase-to-phase voltage is generated; this flux has a certain modulus and phase. On the other side branch 13, a magnetic flux with the same modulus is also generated, since this branch is also connected to the phase-to-phase voltage, and a balanced voltage system and a phase shift of 120 degrees are generally assumed. By properly choosing the connection and direction of the windings, the vector addition of the two fluxes flowing through the central branch 11 has the same modulus and a phase shift of 240 degrees. Thus, the same amount of magnetic flux flows through the three branches 11 , 12 , 13 . In the side branches 12, 13 it is produced by the windings and in the central branch due to their vector sum.

The windings 22, 32, 21 and 31 in the side columns 12 and 13 can be adjusted according to the insulation distance, current density, etc. Associated traditional standards to design. Its design can be conceived taking into account the special characteristics associated with traction transformers, such as heavy overloads, frequent surges, etc. involving severe power dynamic demands.

As better illustrated in FIG. 2 , the power transformer 100 comprises a first set of bushings 4 adapted to operatively connect a first phase 20 and a second phase 30 to a power line, ie schematically indicated by reference numeral 1 in FIG. 1 . The outgoing high-voltage three-phase power lines are interconnected. Furthermore, the transformer 100 comprises a second set of bushings 40 adapted to operatively interconnect the first phase 20 and the second phase 30 with at least one electrical device (not shown in the figure), in particular with a medium voltage power system stand up.

The first set of bushings 4 comprises: a first high voltage bushing 4C connected to the primary winding 22 of the first phase 20 ; a second high voltage bushing 4A connected to the primary winding 32 of the second phase 30 ; And a third high voltage bushing 4B connected to both the primary winding 22 of the first phase 20 and the primary winding 32 of the second phase 30 . The high voltages 4A, 4B, 4C are connected to the three-phase power line 1 and may for example be constructed by high voltage bushings of the capacitive type.

Correspondingly, the second set of bushings 40 comprises: a first bushing 40A and a second bushing 40B connected to the secondary winding 21 of the first phase; and a third bushing 40C and a fourth bushing 40D, Both are connected to the secondary winding 31 of the second phase 30 . One of the bushings 40A or 40B connected to the secondary winding of the first phase 20, as the first bushing 40A is connected to ground; likewise, the third bushing 40C connected to the secondary winding 31 of the second phase 30 and one of the fourth bushings 40D, such as the third bushing 40C, is connected to ground.

Such bushings 40A- 40D can be formed, for example, by capacitive ceramic bushings.

Thus, the primary or high voltage windings 22 and 23 are connected in a V-V configuration, while the secondary or medium voltage windings 21 and 31 are connected in series. Obviously, many other connection configurations are possible, especially for the secondary winding, depending on the application and/or specific needs.

Figure 5 shows the connection layout for the different windings forming a V-V connected transformer. The two single-phase high voltage windings 22 in this example are provided with adjustment taps 23 and a current transformer 24 on the medium voltage output side can be seen for supplying measuring and protection equipment in the substation where the transformer is installed.

In practice, it was found that the power transformer according to the invention fully achieves the intended purpose with several advantages over the prior art. In fact, as mentioned above, the present power transformer 100 has a very compact design in which all windings are V-V connected and in a single electromagnetic circuit with a single monolithic three-leg magnetic core. Due to this compact configuration, the V-V connected two-phase power transformer has an optimal design in terms of its weight and size, and represents a major improvement over new transformers of the V-V connected type (or a replacement for currently installed equipment), since it is more efficient than the available Existing technical solutions for this type of connection are cheaper. Therefore, the investment required for manufacturing, purchasing and the space required for the location of the transformer are optimized. As an example of this implementation, for a 32MVA power transformer with a primary voltage of 110kV, the size of the machine can be reduced to about 6m in length, about 5.7m in width and about 5.1m in height. The total weight can also be reduced to about 75 tons, and this can lead to further advantages in terms of transport costs, since, for example, the transport weight of the heaviest part up to 120 tons is considered suitable for road transport, and above this level The weight needs to be transported by rail.

As indicated above, the power transformer according to the invention is suitable for application in electric traction, and in particular for electrified railway power systems. Therefore, the utility model also relates to a power system, especially an electrified railway traction power system, including:

- power lines, i.e. high voltage power lines 1;

One or more electrical devices suitable to be supplied by said power line, comprising for example a one-phase medium voltage power system; characterized in that it comprises a power transformer 100 as described above, operatively connected to said power line and to said one or between multiple electrical devices.

The power transformer thus conceived is susceptible to modifications and variants, all of which fall within the scope of the inventive concept; all details can furthermore be replaced with technically equivalent elements. For example, bushings may be manufactured in different configurations, or may be placed in different positions or make different electrical connections. In practice, the materials used may be any according to requirements and the state of the art, as long as they are compatible with the particular application and dimensions.

Claims (10)

1. A power transformer for electric traction, characterized in that it comprises: - box (3); - a single magnetic core (10) located inside said box (3) and comprising three branches (11, 12, 13), of which one branch (11) is in the center and two branches (12, 13) Located on both sides of the central branch (11); - a first phase (20) comprising a primary winding (22) and a secondary winding (21) wound on one of said three branches (11, 12, 13); - A second phase (30) comprising a primary winding (32) and a secondary winding (31) wound on the other of said three branches (11, 12, 13). 2. The power transformer according to claim 1, characterized in that the primary winding (22) and the secondary winding (21) of the first phase (20) are wound on the side branches (12, 13) The first (12, 13) is on. 3. The power transformer according to claim 2, characterized in that the primary winding (32) and the secondary winding (31) of the second phase (30) are wound on the side branches (12, 13) On the second (13, 12). 4. A power transformer according to any one of claims 1-3, characterized in that the central branch (11) constitutes a return path for the magnetic flux circulating through the side branches (12, 13). 5. A power transformer according to any one of claims 1-3, characterized in that it comprises a first set of bushings (4) for operatively interconnecting said first phase and said second phase with a power line link up. 6. A power transformer according to any one of claims 1-3, characterized by comprising a second set of bushings (40) for operatively connecting said first phase and said second phase to at least one Electrical devices are interconnected. 7. The power transformer according to claim 5, characterized in that said first set of bushings comprises: a first high voltage bushing connected to the primary winding of said first phase; a second high voltage bushing , which is connected to the primary winding of the second phase; and a third high voltage bushing, which is connected to both the primary winding of the first phase and the primary winding of the second phase. 8. The power transformer of claim 6, wherein said second set of bushings comprises: a first bushing and a second bushing connected to said secondary winding of said first phase; and a third bushing and a fourth bushing connected to said secondary winding (31) of said second phase. 9. The power transformer of claim 6, wherein one of said first and second bushings connected to the secondary winding of said first phase is connected to ground; and connected to said second One of said third and fourth bushings of the secondary winding of the phase is connected to ground. 10. An electrical system for electric traction comprising: -power line; - One or more electrical devices adapted to be powered by said power line, characterized in comprising a power transformer according to claim 1 operatively connected between said power line and said one or more electrical devices.

Images