WO1998038657A1

WO1998038657A1 - Electric transformer for traction, the primary winding consisting of tubular conductors through which cooling fluid flows

Info

Publication number: WO1998038657A1
Application number: PCT/IT1997/000170
Authority: WO
Inventors: Giuseppe Marchegiani
Original assignee: Sirten Srl
Priority date: 1997-02-26
Filing date: 1997-07-16
Publication date: 1998-09-03
Also published as: IT1290551B1; ITMI970420A1; AU3557997A

Abstract

Electric transformer (10) especially for traction purposes, with the primary winding (11) obtained from axial modules (12-15) formed of pairs of coils (20, 21) made by turns of a single layer of tubular conductors (30, 40) inside which cooling fluid circulates, connected electrically in series and hydraulically in parallel.

Description

Electric transformer for traction, the primary winding consisting of tubular conductors through which cooling fluid flows

The invention concerns electric transformers especially for rail traction.

One of the most important problems in rail traction is the weight and bulk of components.

Where feed is by alternating current single-phase voltage is 15-25 kV and is supplied through an insulated overhead cable, here called a "catenary", with one wire grounded to the rails.

One of the heaviest and most bulky components is the transformer which reduces catenary voltage to 800-1000 V for the secondary windings.

The secondary windings supply traction and auxiliary equipment at even lower voltages.

The transformer consists as usual of a magnetic core and of windings formed of insulated wiring. For purposes of insulation and cooling these windings are enclosed in a tank full of oil.

The tank with oil weighs about one tonne and can represent as much as half the weight of the magnetic core and windings.

Purpose of this present invention is to eliminate the tank and a large quantity of the oil.

Subject of the invention is an electric transformer especially for purposes of traction, in which the primary winding consists of turns of a tubular conductor, inside which cooling fluid circulates, divided into a number of modules connected electrically in series and hydraulically in parallel. Cooling fluid may be oil, deionized water or some other. The modules of the windings consist of substantially equal pairs of coils each wound spirally in a single layer in the form of a circular discoid crown so as to be equal from the electromagnetic standpoint, superimposed and electrically and hydraulically connected internally to the coil terminals, both electric and hydraulic, on their external circumferences. The superimposed modules are mounted with the electric terminal of the first module grounded, in particular to the rails for rail traction, and with the terminal of the last module connected to the user apparatus, in particular to the overhead cable for rail traction.

The modules are hydraulically connected in parallel by a first and second group of tubes of insulating material and of constant diameter, leading to two manifolds for inflow and outflow of fluid respectively.

Each module is advantageously connected to the module, above or below, by a T-joint each one connected to a tube for fluid inflow and outflow, so that a single inflow tube and a single outflow tube ensure circulation of the fluid to two adjacent modules. The manifolds for inflow and outflow of fluid are preferably placed at the position of the first module, electrically grounded, so that the various subsequent modules are connected to said manifolds by tubes that do not cross one another and remain substntially parallel, placed at the surface of the cylinderical body formed by the windings, their length increasing as they connect up the modules farthest from the first one. The various superimposed modules therefore present a voltage to earth and a distance from it that increase in the same proportion. The whole winding is immersed in a body of resin from which emerge, substantially on the same side, the grounding terminal, the terminal of maximum voltage and the terminals of the maniforlds for inflow and outflow of cooling fluid.

In a preferred type of execution the terminal is for 10-25kV with a grounded terminal. In one variation the pairs of coils, with tubular conductors inside which the cooling fluid circulates, are interposed between two pairs of coils with solid conductors, all coils being electrically connected in series. If the primary winding is followed by an axial one the output of maximum voltage is placed between the two windings, while the two grounding terminals are placed at the two ends of the cylinder formed by the two windings.

The secondary windings can be placed inside or outside the primary winding. The invention offers evident advantages.

Not only is the tank eliminated but there is also a drastic reduction in the amount of oil so much so that transformers made according to the present invention can be called "reduced oil transformers". Weight of the oil contained in the tubular windings, of both high and low voltage, is about 5% of that needed in the tank of a conventional transformer.

This is a great advantage not only from the aspects of weight and bulk but also from that of safety, oil being an inflammable material. As the voltage towards ground of the various modules increases together with the length of the insulating tubes connecting them to cooling fluid, these tubes can always carry the required voltage. For example if, compared with the first connecting tube subjected to nought voltage, the last one can carry 25 kV, its length will be suitable for that voltage. There can obviously be ten modules like those illustrated, but there can also be a different number.

As the tubes connecting the modules to the manifolds for inflow and outflow of fluid are so laid that they do not cross one over another, on a generator of the cylinder formed by the windings, the sum of said tubes makes only a negligible increase to the cylinder's diameter.

Characteristics and purposes of the invention will be made still clearer by the following examples of its execution illustrated by diagrammatically drawn figures Fig. 1 Transformer with a primary winding formed of modules, each consisting of a pair of coils with tubular conductors, a cross section.

Fig. 2 Detail of a pair of coils, plan view.

Fig. 3 Transformer showing the cooling system, plan view. Fig. 4 As above, side view.

Fig. 5 Transformer with a winding formed of modules each of which consists of three pairs of superimposed coils, two pairs with solid conductors and an intermediate pair with tubular conductors.

Fig. 6 The transformer in Fig. 1 , a conventional drawing. Fig. 7 The transformer in Fig. 5, a conventional drawing.

Fig. 8 Transformer with two primary windings, a conventional drawing of a cross section.

The transformer 10 subject of the invention, comprises the 25 kV primary winding 1 1 , consisting of a number of piled up modules 12, 13, 14, n,- 15 each formed of a pair, a first coil 20 and a second coil 21 , these being respectively an upper one and a lower one.

Each coil consists of a flat spirally wound tubular conductor 25 forming a circular discoid crown.

The two coils 20 and 21 of each module are superimposed, they match from the electromagnetic standpoint, and are coupled in series both electrically and hydraulically, as seen by the bridge 26, so that the two hydraulic terminals 35, 45 and electric 52, 56 of each module both lie on its external circumference.

The winding is served by a tubular manifold 30 for inflow of oil and by a tubular manifold 40 for outflow of oil.

The first coil 20 of the first module 12 is hydraulically connected, by the insulating tube 31 , to the inflow manifold 30, and is electrically grounded, by the wire 51 , to the rails 50.

The second coil 21 of said first module 12 is hydraulically connected, through the T-joint 46 and insulating tube 41 , both to the first coil 20 of the second module 13 and to the outflow manifold 40, and is electrically connected by the bridge 53 to said first coil 20. The second coil 21 of the second module 13 is hydraulically connected, through the T-joint 36 and insulating tube 32 both to the first coil 20 of the third module 14 and to the inflow manifold 30, and is electrically connected by the bridge 54 to said first coil 20 of the module 14, and so on until the last T-joint 47 and insulating tube 43 are reached.

The terminal 56 of the second coil 21 of the last module 15 is hydraulically connected, through the tube 33, to the inflow manifold 30, and is electrically connected to the catenary by wire 57-58. The various connecting tubes of insulating material, like the inflows 31-33 between the complexes 12-14, n, 15 and the inflow manifold 30 and similarly the various connecting tubes of insulating material, like the outflows 41 -43 and the outflow manifold 40, lie on the surface of the cylinder formed by the winding without one crossing over another so that the total tubes 31-33 and 41-43 make only a slight increase in the diameter of the cylinder (Figs. 3 and 4).

As the figures clearly show, the system adopted to create the windings causes oil or other cooling fluid to flow in and out, at points in the winding where the voltage is gradually increasing, through tubes whose lengths also gradually increase. The first complex close to the manifolds, as already explained, has a grounded terminal that represents the start of the winding. Voltage of the second terminal will be V/n, n being the number of complexes. This is possible as voltage to ground of the various superimposed com- plexes and distance to ground increase in the same proportion.

It is therefore clear that as voltage towards ground of the various complexes gradually increases, the length of the insulating tubes for connection to the manifolds also increases. This means that the tubes can always carry the voltage to which they are subjected, namely the voltage between the terminal in each complex 12- 15 and the grounded manifold.

As the Figures show, voltage between the terminals of each complex is 2.5 kV. The last tubes 33, 43 carry a voltage of 25 kV but they are also those of maximum length and are therefore suited to this voltage. There are ten complexes in the figure but there can obviously be a different number. The whole of the winding 1 1 is immersed in a body of resin 9 shown by a dotted line in the figures.

From this body of resin emerge the grounded terminal 50, the 25 kV cable 57, 58 and the terminals of tubes to the inflow 38 and outflow 48 manifolds for the oil. The secondary windings of the transformer are placed inside or outside the primary winding and can also be immersed in resin. Fig. 5 illustrates a variation of the transformer 60 comprising the winding 61 obtained from a series of modules 62, 63, 64, n, 65 each formed of three pairs of coils. The central pair of coils 20' 21 ' is formed of tubular conductors for circulation of cooling fluid and substantially possesses the same characteristics as the pairs of coils 20, 21 forming part of the winding 1 1 seen in Fig.1. Said pair of coils 20' 21 ' lies interposed between two pairs of coils 70 and 71 formed of the normal type of solid conductor, these of course being cooled by the coil placed between them.

Connections among modules are made by electric bridges 53, 54, n , 55. All the other structural and connecting means are similar to those described in Fig. 1 . They are therefore given the same numbers and descriptions of them are not repeated. There will be a considerable difference in heat between the coils wound with solid conductors and the intermediate pair wound with tubular conductors, but this is not damaging as the temperature of the coil wound with a tubular conductor is relatively low on account of the oil circulating inside it. The pairs wound with solid conductors are of course suitably insulated for their working temperatures. Compared with the system first described, the thermal flow of this variant is higher between the circulating tubes and the oil, but to compensate for that less oil is required and at lower pressure.

There are fewer pairs with tubular connductors than in the type described in Fig. 1 but, as will be clear from Fig. 5, each pair requires two tubes for connection to the inflow 30 and outflow 40 oil manifolds.

The number of such tubes will therefore be twice the number of modules.

Figures 6 to 8 illustrate windings the same or similar to those already described, represented in what may be called a conventional manner. For example Figures 6 and 7 show the same type of winding as in

Figures 1 and 5.

Figure 8 illustrates a transformer 10' with two primary windings 11 and 11 ' placed in line.

The terminal of maximum voltage 56 is at the centre and is connected to the utilizing apparatus by the cable 57-58 while the two grounded terminals 50, 50' are placed one at each end.

Claims

1. Electric transformer (10, 10', 60), used especially for traction work, characterized in that the primary winding (1 1 , 11 ', 61) consists of turns of tubular conductors (25) inside which cooling fluid flows, and is divided into a number of modules (12-15, 62-65) connected electrically in series and hydraulically in parallel.

2. Transformer (10, 10', 60) as in claim 1 , characterized in that the cooling fluid is oil.

3. Transformer (10, 10', 60) as in claim 1 , characterized in that the cooling fluid is deionized water.

4. Transformer (10, 10', 60) as in claim 1 , charcterized in that the various modules (12-15, 62-65) forming the windings (11 , 11 ', 61) are coils (20, 21 , 20', 21 ', 70, 71) wound spirally in the form of a discoid circular crown.

5. Transformer (10) as in claim 1 , characterized in that the modules (12-15) of the winding (1 1) are pairs of substantially equal coils (20, 21), each wound spirally in a single layer to form a discoid circular crown so that they match from the electromagnetic standpoint, and are superimposed and internally connected, both electrically and hydraulically, with the electric (52, 56) and hydraulic (35, 45) terminals on their external circumference.

6. Transformer (10) as in claim 1 , characterized in that the modules (12-15) are mounted superimposed, with the electric terminal (52) of the first module (12) grounded (50) especially to the rails for railway traction, and with the terminal (56) of the last module (15) connected to the user apparatus, especially to the overhead cable for said form of traction.

7. Transformer (10) as in claim 1 , characterized in that the modules (12-15) are hydraulically connected in parallel by a first (31 -33) and a second group of tubes (41-43) of insulating material, of a constant diameter, connecting with two manifolds (30, 40) respectively for inflow (30) and outflow (4) of cooling fluid.

8. Transformer (10) as in claim 7, characterized in that each module (12-15) is connected to an upper module or a lower module by a T-joint (36, 46, 47) each joined to a tube for outflow (41-43) or inflow (31 -33) of the fluid, so that a single tube (31 - 33) for inflow of fluid and a single tube (41 -43) for outflow of fluid ensure ciriculation of fluid to two adjacent modules (12, 13), (14, n,), ( n, 15).

9. Transformer (10) as in claim 7, characterized in that the inflow (30) and outflow (40) manifolds for the fluid are placed at the position of the first module (12) electrically (41) grounded (50) so that the subsequent modules (13-15) are connected to said manifolds by tubes (31 -33, 41 -43), that do not cross over each other but remain substantially parallel, placed on the surface of the cylinder formed by the winding (11), their length gradually increasing as they connect up with the modules farthest from the first one, so that voltage to ground of the superimposed modules and their distance from ground increase in the same proportion.

10. Transformer (10) as in claim 1 , characterized in that the whole of the windings (1 1 , 1 1 ', 61) is immersed in a body of resin (9) from which emerge, substantially from the same side, the grounding terminal (50), the maximum voltage terminal (58) and the terminals (38, 48) of the inflow (30) and outflow (40) manifolds for the cooling fluid.

11. Transformer (10) as in claim 1 , characterized in that it is a 10-25kV transformer with a terminal (52) to ground (50).

12. Transformer (60) as in claim 5, characterized in that the pairs of coils (20' 21 ' with tubular conductors carrying cooling fluid , are interposed between two pairs of coils (70, 71) with solid conductors, all coils (20', 21 ' 70, 71) being electrically connect- ed in series.

13. Transformer (10') as in claim 1 , characterized in that the primary winding (1 1 ) is followed by another axial winding (11 ') with the electric output terminal (58) laid between the two windings (11 , 11 ') while the two grounding terminals (50, 50') are placed at the two ends of the cylinder formed by the two windings (1 1 , 11 ').

14. Transformer as in claim 1 , characterized in that the secondary windings (11 ') are placed inside the primary winding.

15. Transformer as in claim 1 , characterized in that the secondary windings are placed outside the primary winding.