Electrical device with dynamic winding pressing

Abstract

An electrical device for connection to a high-voltage system includes a magnetizable core, at least one winding which encloses a section of the core, a tank which is filled with insulating fluid and in which the core and each winding are disposed, and at least one pressing element, which is surrounded by insulating fluid, for generating a winding pressure. The pressing element is supported on the core and the winding. In order to adjust the winding pressure from the outside in a simple and cost-effective manner, the pressing element is provided as a drivable pressing element and is connected to an actuating unit. The actuating unit is configured to set the winding pressure which is generated by the pressing element.

Claims

1. An electrical device for connection to a high-voltage system, the electrical device comprising: a tank filled with insulating fluid; a magnetizable core disposed in said tank; at least one winding enclosing a section of said magnetizable core, said at least one winding being disposed in said tank; at least one drivable pressing element for generating a winding pressure, said at least one drivable pressing element being surrounded by insulating fluid and being supported on said magnetizable core and said at least one winding; said drivable pressing element forming a hydraulic chamber being filled with hydraulic fluid; said winding pressure being determined by a pressure of the hydraulic fluid in said hydraulic chamber; a compensation device coupled to said hydraulic chamber to compensate for temperature-related fluctuations in a volume of the hydraulic fluid; and an actuating unit being connected to said drivable pressing element and being configured to set said winding pressure generated by said drivable pressing element.

2. The electrical device according to claim 1, wherein: said drivable pressing element is an electrically drivable pressing element; an electrical connection line connects said electrically drivable pressing element to said actuating unit; and said actuating unit has an output end providing a predeterminable electrical voltage or a predeterminable electric current.

3. The electrical device according to claim 1, wherein said compensation device includes a moving part fluid-tightly delimiting said hydraulic chamber and a spring device supporting said moving part.

4. The electrical device according to claim 3, wherein said actuating unit is a mechanical actuating unit and is configured to set a spring pressure of said spring device.

5. The electrical device according to claim 3, wherein: said compensation device has a compensation cylinder in which said moving part and said spring device are disposed; a working cylinder is supported on said magnetizable core and said at least one winding and generates said winding pressure; and a hydraulic line connects said compensation cylinder to said working cylinder.

6. The electrical device according to claim 3, which further comprises: a working cylinder; said moving part being a piston movable in said working cylinder; said piston and said working cylinder together defining said hydraulic chamber; and said spring device supporting said piston on said magnetizable core or said at least one winding.

7. The electrical device according to claim 1, wherein the hydraulic fluid and the insulating fluid are identical.

8. The electrical device according to claim 1, wherein said actuating unit has a hydraulic pump coupled to said hydraulic chamber.

9. The electrical device according to claim 1, wherein said actuating unit is disposed outside said tank.

10. The electrical device according to claim 1, which further comprises at least one dimensionally stable spacer disposed between said magnetizable core and said at least one winding for providing a minimum winding pressure.

11. The electrical device according to claim 1, which further comprises a sensor for detecting said winding pressure, and a display element connected to said sensor for displaying said winding pressure.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) Further expedient refinements and advantages of the invention are the subject matter of the following description of exemplary embodiments of the invention with reference to the figures in the drawing, wherein identical reference symbols refer to identically acting components and in which

(2) FIG. 1 shows a schematic side view of a first exemplary embodiment of the electrical device according to the invention, and

(3) FIG. 2 shows a schematic lateral view of a further exemplary embodiment of the electrical device according to the invention.

DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows an exemplary embodiment of the electrical device 1 according to the invention which is designed as a transformer. The transformer 1 has a fluid-tight tank 2 in which a core 3 is arranged. The core 3 has a magnetizable section which is formed from steel sheets which bear against one another and forms limbs 4 which, in the exemplary embodiment shown, are each concentrically surrounded by three partial windings 5, 6 and 7. The core limbs 4 are connected to one another at their top end by a likewise magnetizable upper yoke 8, wherein the upper yoke 8 is compressed from both sides by a pressing frame 9. The non-magnetizable pressing frame 9 is designed in an L-shape as a constituent part of the core 3 in the exemplary embodiment shown and has a shoulder 10 which protrudes out of the plane of the drawing and which extends at a right angle to a contact-pressure limb 11 which extends parallel to the upper yoke 8. A winding ring 12 which can be displaced in the indicated longitudinal direction 13 and rests on the end sides of the windings 5, 6 and 7 is shown above the windings 5, 6, 7. Drivable pressing elements 14 which each have a working cylinder 15 in which a piston 16 is guided such that it can move in the longitudinal direction 13 are supported on the winding ring 12 at one end and the shoulder 10 at the other end. The working cylinder 15 and the piston 16 bound a hydraulic chamber 17 which is filled with a hydraulic fluid. The piston 16 bears against the inner wall of the working cylinder 15 in a fluid-tight manner with the aid of sealing means. Spring means 18 which are supported on the piston at one end and on the inner wall of the working cylinder 15 at the other end are provided on that side of the piston 16 which is averted from the hydraulic chamber 17.

(5) Two actuating units 19 which are connected to the spring means by means of a mechanical connection 20 are shown outside the tank 2. The actuating unit and the mechanical connection allow adjustment of the spring characteristic of the spring means 18. For example, the spring can be pretensioned to a greater extent by means of the mechanism 20, as a result of which the spring characteristic changes and, at the same time, the contact pressure of the winding ring 12 on the winding end sides or, in other words, the winding pressure is increased.

(6) When the insulating fluid within the tank 2 is heated, the hydraulic fluid in the hydraulic chamber 17 is also heated, wherein the hydraulic fluid expands. The piston 16 is pushed upward in the process. This leads to further compression of the spring means 18. In this case, the winding pressure increases, but to a considerably reduced extent in comparison to the refinement without springs. The increase in the winding pressure can be predetermined with the aid of the spring characteristic. In order to be able to maintain a minimum winding pressure if there is a defect in the hydraulic system, for example if there is a leak in the hydraulic chamber 17, dimensionally stable spacers 30 are arranged between the core, here the contact-pressure limb 11, and the winding ring 12. It goes without saying that the winding ring 12 is composed of a non-deformable material.

(7) FIG. 2 shows a schematic lateral view of a further exemplary embodiment of the transformer 1 according to the invention. The exemplary embodiment shown in FIG. 2 differs from the refinement shown in FIG. 1 schematically in terms of the configuration of the pressing elements 14. The pressing elements 14 are no longer directly supported on the winding ring 12. Instead, enclosures 21 which allow less expansive pressing elements to be used are provided. The pressing element 14 shown in FIG. 2 is a commercially available hydraulic cylinder which is called working cylinder 15 here. A portion of the hydraulic chamber 17 which is bounded there by a moving piston is formed in the working cylinder 15. The piston which is guided in a fluid-tight manner is equipped with a piston rod 22 which extends out of the working cylinder 15.

(8) A compensation vessel 23 which has a moving part 24 which is arranged in a compensation cylinder 26 and is guided in said compensation cylinder in a fluid-tight and movable manner is shown outside the tank 2. A hydraulic line 27 extends between the compensation cylinder 26 and the working cylinder 15. In this exemplary embodiment, the hydraulic chamber is bounded by the moving part 25, the piston, not illustrated in the figure, of the working cylinder 15 and the hydraulic line 27. Spring means 18 which serve to compensate for temperature-related fluctuations in the volume of the hydraulic fluid 17 are supported on that side of the moving part 25 which is averted from the hydraulic chamber. The piston rod 22 which protrudes out of the compensation cylinder 26 is not supported against any components and is therefore freely movable in the longitudinal direction 13. Furthermore, the compensation means 23 comprise a hydraulic pump 28 and a pressure display 29 which is connected to a pressure pickup, not illustrated in the figure and arranged in the hydraulic chamber, and displays the pressure prevailing in the hydraulic chamber. The hydraulic pump 28 is an actuating unit within the meaning of the invention and allows the winding pressure to be set in the desired manner. If, for example, the winding pressure is to be increased, the hydraulic pump 28 is switched on, so that the hydraulic pressure both in the compensation cylinder 26 and also in the working cylinder 15 increases. In accordance with said pressure increase, an increased force is introduced into the end sides of the windings 5, 6 and 7 by means of the piston rod 22, the enclosures 21 and the winding ring 12. This increases the winding pressure.

(9) A further variant of the apparatus according to the invention is illustrated in dashed lines in FIG. 2. In this refinement of the invention, the compensation element 23 is no longer arranged outside the tank 2, but rather within the fluid space of the tank 2. The compensation means 23 again comprise a compensation cylinder 26 with a moving part 25 which is guided in a movable manner in the compensation cylinder and bounds a hydraulic chamber in said compensation cylinder in a fluid-tight manner, said hydraulic chamber being formed by a portion of the compensation cylinder 26, the connecting line 27 and a portion of the working cylinder 15. A separate actuating unit, which serves to change the spring characteristic of the spring means 18, is not illustrated in the figure. Here, the compensation means 23 are arranged in the upper region of the tank 2, which has a hand hole, not illustrated in the figure, which can be opened from the outside, so that access to the compensation means 23 is possible. In this example, the actuating unit is integrated in the compensation cylinder 26 and can be adjusted from the outside through the hand hole.