DD254461A1 - FUSE FOR ELECTRIC POWER CAPACITORS - Google Patents

Abstract

The invention relates to a fuse for self-healing power capacitors for high operating voltages and high operating currents, the z. B. be used in power electronics. The invention is a technical solution to be specified, which ensures that after the response of the fuse secure isolation of the separation distance is achieved. According to the invention this is achieved in that the connection between the connecting wire containing the predetermined breaking point and the winding via an elastic connection piece takes place.

Description

Object of the invention

It is an object of the invention to provide a fuse for electrical capacitors, which ensures a simple means of reliable isolation of the separation distance, even at high operating voltages.

Explanation of the essence of the invention

The object of the invention is to provide a technical solution of a fuse for electric power capacitors, which can be easily implemented and ensures that after switching off the active part of the capacitor is safely disconnected from the mains.

According to the invention this is achieved in that the connection of the lead wire, which contains a predetermined breaking point, with the capacitor winding via an elastic Anschlußstück which is dimensioned so that it can bend elastically at a force corresponding to the Abreißkraft by a certain amount ,

embodiment

In one embodiment, the solution according to the invention will be explained with reference to a drawing. The accompanying figures represent:

Fig. 1: capacitor with fuse, overall view in section

Fig. 2: junction winding / connector / lead wire with breaking point in normal operating condition Fig. 3: junction winding / connector / lead wire at overpressure in the capacitor before tearing off the fuse

Fig. 1 shows a built-in a housing 1, constructed of two parallel windings 2 capacitor. The connecting wire 3 has a predetermined breaking point 4. The connecting wires 3 and 5 are guided through oil-tight connections 6 through the lid 7. The connection of the lead wire 3 to the coils 2 via the connecting piece 8. The winding 2 are locked by a bead 9 in the housing.

When an overpressure occurs in the condenser interior, the lid 7 begins to buckle. On the connecting wires 3; 5 acts a tensile force, which causes a deflection of the elastic connecting piece 8. The force required for the deflection increases with the deflection. Upon reaching the breaking force breaks the breaking point 4 and the connector 8 springs back and provides a safe Isolierstrecke ago.

In the capacitor produced in this way is dispensed with the otherwise very rigid clamping of the predetermined breaking point containing lead wire 3. A rigid connection causes, especially in large-volume capacitors already at very low pressure shutdown occurs. However, as practice shows, this is not necessary and not desirable in every case. With a rigid structure is further noted that break even by improper work on the terminals 6 or by a brief warming of the capacitor above the allowable Abreißsicherungen and the capacitor is unusable without the active part of the capacitor has a damage.

With the structure according to the invention it is achieved that the shutdown takes place only at a higher internal pressure. Low overpressures are compensated. When switching off a sufficiently large insulating distance is created. During assembly no bias must be made. The desired deflection can be easily achieved by varying the width or thickness of the fitting 8 or the distance of the lead wire 3 from the inner wall of the core tube. For oil-filled capacitors, deflections "a" of 1 to 3 mm are generally sufficient if it is ensured that the impregnating oil can penetrate into the insulating section.

Claims (3)

claims: 1. fuse for power capacitors, which consist of one or more wound on stable core tubes circular windings and have a responsive to overpressure fuse, characterized in that the provided with a predetermined breaking point connecting wire via an elastic connecting piece, which is up to a force that the tearing force corresponds to the predetermined breaking point, can elastically deflect by a certain amount, is connected to the winding. 2. Fuse for power capacitors according to claim 1, characterized in that the deflection is adjusted for a given break-off force by varying the thickness or width of the connecting piece or the distance of the connecting wire containing the predetermined breaking point of the core tube inner wall. 3. fuse for power capacitors according to claim 1 and 2, characterized in that the amount for the deflection is preferably 1 to 3 mm when reaching the tearing force. For this 1 page drawings Field of application of the invention The invention relates to a fuse for power capacitors, which are suitable for high operating voltages and high operating currents. Such power capacitors are z. B. used as erase, support or smoothing capacitors in power electronics. Characteristic of the known state of the art It is known to provide self-healing capacitors with an overpressure protection that separates the capacitor at electrical overload or at the end of the life of the network, so that a bursting of the housing is prevented. To trigger the fuse used by the gas formation due to Selbstheildurchschlägen or by heat generation internal pressure. This overpressure is used in cylindrical capacitors either for the opening of a compressed bead or for buckling of the bottom or lid, in prismatic capacitors mostly to the curvature of the lateral surfaces. In general, tightly tensioned tear-off wires are separated at a predetermined breaking point, so that the flow of current is interrupted. Examples of such predetermined breaking points are i.a. in DE-PS 1289584, DE-PS 2220022 or DE-OS 3047876. The disadvantage here is that, in particular for capacitors for higher nominal voltages, the production of a sufficiently large Isolierstrecke at the point of interruption is associated with problems. In the case of considerable defects in the interior of the condenser or in the case of very heavy overload, a steep pressure increase can usually be achieved in a short time, which causes an irreversible curvature of the cover or bottom or a clear opening of the compressed bead, whereby a sufficiently large insulating distance is produced. With slow aging or relatively low overload, coupled with slow pressure rise inside the capacitor, however, is often recorded that a sufficient Isolierstrecke is achieved. For capacitors of larger dimensions, where usually the bottom or lid curvature is used for shutdown, the curvature is often still in the range of elastic deformation, so that it z. B. decreases in the internal pressure due to minor leaks to the decline of the curvature associated with flashovers and arcs in the condenser interior. Also, the capacitors often do not pass the prescribed tests of the internal breaker. The test regulations generally require that after switching off a certain test voltage between the terminals withstand without rollover. A technical solution for creating a sufficiently large isolation gap after shutdown is e.g. DD-WP 223288. It is used a trigger mechanism, which has a braced spring element and a knife-like separator. The mechanism is actuated by a trigger, which is triggered by the curvature of the housing wall. This technical solution requires a high production cost and is only applicable to large capacitor units. In DE-OS 2926558 a technical solution for capacitors of small design is given. The connection to the outer terminals via spring plates, which are in pressure contact with the inner leads. This solution is not applicable to high-current capacitors, with large contact resistances occurring at the contact point. In pulse discharges of the capacitors arcs may occur at the transition points. A specified in DE-GM 8114739 solution, however, is suitable for higher currents and pulse discharges. The isolation of the separation distance is achieved in that a special plate-shaped spring element is used, which receives a bias voltage during assembly of the capacitor. The disadvantage of this technical solution, however, is that the generation of the bias in the assembly process is technically complicated. The mechanically sensitive predetermined breaking point is heavily stressed during assembly. The conditions are industrially difficult to reproduce.