Description

The invention is related to a vehicle transformer, comprising a transformer core with two opposed yokes and at least two limbs extending inbetween them along a parallel limb axis, wherein a support structure is foreseen at each of the yokes for carrying the vehicle transformer with horizontal oriented limb axis and wherein a hollow cylindrical coil with at least one respective electrical winding is arranged around at least one of the limbs.

It is known that electrically driven vehicles, especially railway locomotives, require a mobile electrical transformer in order to adapt the voltage level supplied by an electrical supply system through an overhead line for example to the needs of electrical frequency converters or the like which are installed in the vehicle itself. A typical voltage level of an overhead transmission line is in the range of for example 1 kV to 10kV. Normally the frequency converters generate a voltage with a controllable frequency and voltage level for supplying preferably asynchronous motors which drive the vehicle. The rated power of a railway locomotive for example might amount several MVA, wherein the rated power of an electric tram way might amount some 100 kVA.

A transformer is a known component in distribution networks which is normally not subject to major geometrical restrictions. A typical transformer in a distribution network has a vertical oriented limb axis and is not subject to any force impacts such as vehicle transformers are, for example when driving with a high speed of >200km/h into a curve.

In order to increase the useable space in a vehicle such as a train the components required for traction of the train - especially transformers and frequency converters - are arranged in an underfloor area and / or on the roof of the railway vehicle. Thus a typical train does not comprise a dedicated locomotive for traction which pulls several wagons moreover the components for traction are distributed on several wagons which all provide useable space for passengers. This useable space is normally the center area of the railway wagons respectively vehicles.

Disadvantageously within the state of the art is that the electrical components have to be arranged under the passenger space in an underfloor area and / or above the passenger space on the roof of the wagon respectively vehicle in a very limited space. Due to the always limited maximum cross section profile of a train or vehicle the space for arranging such electrical components is very limited, especially concerning its height. Also the weight of a vehicle transformer should be as less as possible so that the energy consumption of the vehicle in operation is reduced therewith.

It is objective of the invention to provide a compact lightweight vehicle transformer with a flat design which is on the other side robust against impacts respectively vibrations which occur while the vehicle is in motion.

This problem is solved by a vehicle transformer of the aforementioned kind. This is characterized in that the coil is rigidly connected with the limb so that the flexural resistance of the rigid combination of both is improved therewith compared to a combination of both without rigid connection.

Basic idea of the invention is to arrange the transformer core with horizontal arranged limb axis in order to reduce the height of the required space. Here a support structure is foreseen at each of the yokes for carrying the vehicle transformer with its full weight. Any additional mechanical support of the coil is not required the whole weight of the transformer is worn by the support structures in the yoke areas. The limbs of a conventional stationary transformer are typically oriented vertically, so that the weight of the coils arranged around the limbs respectively the weight of the transformer core itself is easily borne by the transformer core without major flexural burden. On the other side the mechanical strength of a conventional transformer core, which is normally composed of several layers of sheeted metal, is not sufficient to bear its own weight and the weight of its coils in a horizontal position.

Normally a coil which is arranged on the limb of a transformer core is a component which does not improve the mechanical behavior of the core moreover it is a load, which has to be borne by the transformer core. According to the invention the coil is rigidly connected with the limb so that the coil itself increases the flexural resistance of the rigid combination of both. Precondition for this is that the coil itself is also of a rigid structure.

Thus the vehicle transformer according to the invention has a robust structure on one side and is compact in its design on the other side since further components for stabilization are not required. Especially the required height is reduced due to the horizontal arrangement of the limbs respectively coils. By this reason a vehicle transformer according to the invention can become designed in that way that it is placea- ble into the typically standardized space which is available underfloor or on the roof of a vehicle. Due to the reduced weight of the transformer a respective vehicle will also be more environmental friendly.

According to a further embodiment of the invention a fiber composite material is foreseen on the surface of the limb in order to increase its mechanical strength. Typically a transformer core consists of laminated metal sheets to reduce eddy current. A fiber composite material such as resin impregnated glass fiber roving which is hardened in a curing process after applying respectively winding it on the limb will significantly increase the mechanical stability and the flexural resistance of the limb.

According to a further embodiment of the invention limb and coil are rigidly connected at least in part by means of glue. During handling the glue material it is preferably in the liquid state wherein it becomes rigid after hardening so that in can be easily treated. This enables for example that the conductors of an electrical winding are di- rectly wound on the limb respectively a fiber material on the limb without producing a separate coil in advance. The surface of the fiber material gives an improved grip for the glue material compared to the metal sheets of the core itself. A further advantage of this embodiment is that no bobbin or the like is required so that the radial space is used in an optimal way. Examples for a suitable glue are

• Korapox-Zweikomponenten Harz 735A,

• Korapox-Zweikomponenten Harz 735B or

• Scotchcast Kleber Nr. 282.

According to a further embodiment of the invention the hollow cylindrical coil comprises a fiber composite material. The principle to increase the mechanical stability and the flexural resistance of a limb by a fiber composite material can also be applied on a coil. Fiber composite material is typically an electrical insulating material which is required inbetween different layers of electrical conductors anyhow. So no further space is required for increasing the flexural resistance of the coil.

According to the invention the fiber material is preferably arranged in that way that the mechanical stability of the coil is increased in an efficient way. A respective embodiment is characterized in that the hollow cylindrical coil comprises several layers of a wound a fiber composite material in different radial distances along approximately the whole axial extension of the coil so that it has for instance the mechanical strength of a monolithic block. The stability might be improved by applying a band shaped material with a width that is similar to the axial length of the coil so that an axial overlap is avoided. A suitable composite material is for example a resin impregnated glass fiber material or Prepreg, which is a pre-impregnated band-like material, wherein the resin for impregnation is in the B-stage. This means that it is in a solid state but it will be molten during a curing process and hardened thereafter.

According to another embodiment of the invention preferably axially oriented battens are foreseen in a radial space inbetween limb and coil, so that hollow cylindrical arranged axial channels are built. The battens are preferably made from a rigid material and glued on the surface of the limb respectively the surface of a surrounding fiber composite material. In a comparable way the battens are additionally glued on the radial inner surface of the coil. So the battens are fully integrated in the rigid structure of limb and coil. In an advantageous way cooling channels are built therewith so that the vehicle transformer can be cooled during operation in an efficient way. Axial cooling channels can also be foreseen inbetween radial adjacent layers of conductors of the coil.

According to another embodiment of the invention the coil extends along approximately the whole axial length of the limb. So the space for the transformer is used in the most efficient way on the one side and the mechanical stability of the limb is improved along its whole length in an advantageous way.

According to another embodiment of the invention a respective hollow cylindrical coil is arranged around each of the limbs. Also here the available space is used in the most efficient way and the weight of the transformer is not unnecessarily increased therewith. Since the electrical supply of vehicles such as trains is normally realized with only one overhead conductor and a ground connection, a typical vehicle transformer is single phased, so one primary and one secondary winding are foreseen. Optionally a third winding, for example for supplying a heat radiator for the passenger room of a vehicle, might be foreseen. A winding might be divided into two or more parts which are electrically connected in series. Thus a preferred embodiment of the invention is a two limb transformer with two coils, wherein the electrical windings are distributed in that way on the two coils, that they have at least approximately the same size.

According to a further embodiment of the invention the support structure comprises a beam structure from an approximately wave-shaped strip of metal at each yoke, wherein peaks and lows of the beam structure extend along parallel lines.

An underfloor area of a vehicle like a railway wagon is typically prepared to accommodate a certain number of casings respectively modules with a standardized size. In order to make the casings mountable respectively exchangeable in an easy way, at least for the underfloor variant a standardized traverse beam at the bottom of each casing is foreseen at its both axial ends. In order to increase the available height in each casing the height of the traverse beams is reduced and they have an increased width instead. Thus a support structure has to be foreseen at each of the yokes for carrying the vehicle transformer in a vertical distance to the traverse beams. The support structure has to fulfill criteria concerning a minimum weight on one side and a required degree of stiffness on the other side, so that the vehicle transformer is safely mounted on the traverse beams, even in case of horizontal impacts from the side caused for example by an accident.

According to another embodiment of the invention the beam structure is arranged under each of the yokes of the transformer core with horizontal oriented limb axis and connected thereto by at least two screw- or bolt- connections for each yoke extending through the peaks of the beam structure and through the whole thickness of the yokes. Bolts or screws extending through the whole thickness of the yokes provide a save and easily mountable connection, wherein the stability of the transformer core is increased in an advantageous way therewith.

According to another embodiment of the invention a C-profile shaped traverse beam is arranged under the beam structure and connected thereto by at least two screw- or bolt- connections through the lows of the beam structure. The C-profile shape of the traverse beam provides an additional reduction of weight with a high degree of mechanical stability.

According to a further embodiment of the invention the beam structure is designed in that way, that it withstands horizontal impacts from the side. Due to reasons of safety respective regularities exist in different countries, which have to be fulfilled. The design of the beam structure can be modified by adapting the axial width of the wave- shaped strip, adapting the numbers of waves or adapting the thickness of the material for example. A simulation by use of a finite element program can be used to verify suitability of a certain design. A suitable design comprises for example 4 waves with a vertical distance of for example 40cm inbetween peaks and lows, wherein the width of the wave shaped strip amounts 30cm for example.

According to a further embodiment of the invention the vehicle transformer is mounted in an underfloor area of a railway-vehicle. Thus the advantages of a small, light and robust design of the vehicle transformer are implemented into a vehicle. According to a further embodiment of the invention the vehicle transformer is arranged in a casing with a blower for cooling. The casing is made from sheets of steel for example. Since the whole weight of the vehicle transformer is carried by the yokes the casing has no structural function moreover its purpose is to protect the vehicle transformer against environmental conditions such as dust or water. A blower, preferably comprising an air-filter unit, enables a forced air cooling of the transformer. The shape of the casing corresponds preferably to a standardized module size for railway wagons.

According to a further embodiment of the invention the cross section of the yokes respectively limbs is approximately rectangular. Thus the required volume of the vehicle transformer is once more reduced in an advantageous way.

Further advantageous embodiments of the invention are mentioned in the dependent claims.

The invention will now be further explained by means of an exemplary embodiment and with reference to the accompanying drawings, in which:

Figure 1 shows an exemplary first vehicle transformer,

Figure 2 shows a first exemplary coil rigidly connected with a limb,

Figure 3 shows a second exemplary coil rigidly connected with a limb,

Figure 4 shows a vehicle transformer on a beam structure and

Figure 5 shows an exemplary vehicle with vehicle transformer.

Figure 1 shows an exemplary first vehicle transformer 10 from a top view. A ring like rectangular shaped transformer core 12 comprises two yokes 18, 20 and two limbs 22, 24 extending parallel to a limb axis 26 inbetween the yokes 18, 20. A respective hollow cylindrical coil 14, 1 6 is arranged around each of the limbs 22, 24 along their nearly whole axial extension. The limb axis 26 of the vehicle transformer is oriented horizontal so that the vertical required space is reduced therewith. Limbs 22, 24 and coils 14, 1 6 are rigidly connected by means of glue, so that the flexural resistance of the combination of both is improved in an advantageous way therewith. Figure 2 shows a first exemplary coil 46 rigidly connected with a limb 34 in a sketch 30. The limb 34 consists of several layers of stacked metal sheets which have an approximately round common cross section extending around a limb axis 32. On the radial outer side of the limb 34 a wound layer of a fiber composite material 36 is foreseen in order to give the limb 34 an improved mechanical strength. On the radial outer surface of the layer of fiber composite material 36 several axial oriented battens 38, 40 are glued on in an equal tangential distance each to each other. On the radial outer side of the battens 38, 40 a hollow cylindrical coil 46 with a not shown electrical winding is glued on. The hollow cylindrical coil 46 is enforced by several not shown layers of a fiber composite material so that its consistency is stiff. In the radial space inbetween limb 34 and coil 46 hollow cylindrical arranged axial channels 42, 44 are foreseen as cooling channels. Since limb 34 and coil 46 are rigidly connected together by means of glue the combination of both has a mechanical strength of a monolithic block with a high flexural resistance.

Figure 3 shows a section of a second exemplary coil 74 rigidly connected with a limb 54 in a sketch 50. The limb 54 consists of several layers of stacked metal sheets 56 with a circular cross section extending around a limb axis 52, whereas only a part of the cross section is shown in this sketch. A laver of fiber composite material 58 on the radial outer surface of the limb 54 increases its mechanical strength and flexural resistance. The hollow cylindrical coil 74 comprises several alternating layers of fiber composite material 64, 68, 72 and electrical windings 66, 70. Due to the fiber composite material 64, 68, 72, which is also present inbetween the conductor loops of the windings 66, 70, the coil 74 has a stiff consistency and high mechanical strength. Limb 54 and coil 74 are rigidly connected with axially arranged battens 60, which are glued 62 in a radial space inbetween.

Figure 4 shows a vehicle transformer on a beam structure 92 in a sketch 80. The vehicle transformer comprises a transformer core with two opposed yokes 82 and horizontal oriented limbs with respective coils 84, 86 arranged around them. The yokes 82 of the transformer core are borne by a respective wave shaped beam structure 92 which is connected to the yokes by means of bolts 88, 90 at its peaks 96. The bolts 88, 90 are extending through the whole thickness of the yokes 82 so that an increased mechanical stability of the transformer core is gained therewith. The lower side of the beam structure 92 is borne by a traverse C-profile shaped beam 98 which is connected with the lows 94 of the beam structure 92 by further bolts. At both sides of the C-profile shaped beam 98 respective brackets 100, 102 are foreseen in order to connect the whole structure with the underfloor area of a vehicle. The composed shape of the C-profile beam 98 and the brackets 100, 102 corresponds to the outer limit of an exemplary profile which is allowed for the underfloor area of a railway wagon.

Figure 5 shows an exemplary vehicle 1 12 with vehicle transformer in a sketch 1 10. The vehicle 1 12 is a railway locomotive which provides space for three standardized underfloor modules and two roof modules. In one of the underfloor modules a vehicle transformer 1 14 is arranged, wherein the horizontal limb axis 1 1 6 is oriented in driving direction. On one of the roof modules a further vehicle transformer 1 18 is arranged.

List of reference signs

10 exemplary first vehicle transformer

12 transformer core

14 first hollow cylindrical coil of first vehicle transformer

16 second hollow cylindrical coil of first vehicle transformer

18 first yoke of transformer core

20 second yoke of transformer core

22 first limb of transformer core

24 second limb of transformer core

26 limb axis

30 first exemplary coil rigidly connected with limb

32 limb axis

34 limb

36 layer of fiber composite material

38 first axial ly oriented batten

40 second axially oriented batten

42 first axial channel

44 second axial channel

46 coil

50 second exemplary coil rigidly connected with limb

52 limb axis

54 limb

56 metal sheets of limb

58 layer of fiber composite material

60 batten

62 glue

64 first wound layer of fiber composite material

66 first electrical winding

68 second wound layer of fiber composite material

70 second electrical winding

72 third wound layer of fiber composite material

74 coil

80 vehicle transformer on beam structure

82 yoke of transformer core 84 first coil of vehicle transformer

86 second coil of vehicle transformer

88 first bolt

90 second bolt

92 exemplary beam structure

94 low of beam structure

96 peak of beam structure

98 C-profile shaped beam

100 first bracket

102 second bracket

1 10 exemplary vehicle with vehicle transformer

1 12 vehicle

1 14 vehicle transformer mounted in an underfloor area

1 1 6 vehicle transformer mounted in a roof area