Current-detection coil for a current transformer

The invention relates to a current detection coil for a Power converter according to the Rogowski principle with an electric Insulating annular body as a carrier for a winding, wherein The cross-sectional shape of the annular body on the outer circumference and on the circumference Inner circumference has a flattened area.

A current detection coil of this type is through the GB magazine EPE Journal, Vol. 3, No. 1, March 1993, pp. 51 To 59 became known. As forms of annular bodies There simple solid toroids or flexible and cut open Coil body. Furthermore, the use Circular cut plastic rings with rectangular Cross section recommended for attachment to A ladder and then into the ring mold to return.

Although all of the aforementioned embodiments of current detection coils With different annular bodies Formation of a Rogowski current transformer with good transfer behavior Is to be achieved with the standard Manufacture the difficulty that practically every manufactured Has other transfer characteristics and therefore Individual adjustments or electronic correction circuits Must be used to ensure even Results. The dependence of the transmission behavior Of Rogowski current detectors of Slight deviations of their geometrical nature Opposite the ideal form is known and has already led to the Proposal, as a winding beam straight ground To use ceramic bars (DE-Zeitschrift "Technische Mitteilungen AEG-Telefunken "60 (1970) 7, pages 444 to 448). However, since a current detection coil according to the Rogowski principle Must surround a conductor on a closed path, Requires the use of straight ceramic rods Composition of a closed current detection coil Four partial coils. This results in considerable disturbances Field course due to the right angle of the Sections. In order to raise this influence, the Joints are made free by a shield. The The desired precision of the Rogowski current transformer is therefore A considerable expenditure on the production of the current detection coils connected.

SUMMARY OF THE INVENTION The object of the invention is, A construction for a current detection coil of a Rogowski current transformer To create, which is characterized by a minimal The distribution of their properties, Current current measurements as well as for tripping Is.

According to the invention, this object is achieved in that: The remaining areas of the cross-sectional shape are approximately semicircular , In that the annular body is made of a metal strip Fiber reinforced thermosetting plastic and is used as a Solid solid body in a separable form Wherein the annular body is burr-free And has no undercuts and that the Winding by means of a ring core winding machine Is.

The annular body provided according to the invention is a very large one Stable part, which has a high thermal resistance and At the same time a low thermal expansion factor Respectively. These properties mean that the shape The winding changes only minimally when the current detection coil For example on the main flow paths of a Low-voltage circuit breaker is installed where strong Mechanical vibrations and temperatures up to above 100 ° C. This stability is borne only by the Inner and outer circumference Ring body, which is used to measure the resistance moment to a Mechanical deformation. The burr - free production of the Ring body contributes to the desired uniformity and quality Of the winding in that the winding wire runs over the whole Circumference of the annular body is fully supported and therefore not displaced Or deformed.

For use in low-voltage circuit breakers in the Medium to higher rated current range is suitable, for example An annular body having an outer diameter of about 80 To 100 mm, single layer with copper wire of about 0.05 Thicknesses of up to 0.1 mm.

If current detection coils according to the invention are used in multi-pole Low-voltage circuit breakers, so Can be the accuracy of the measurement in the adjacent phases By the small distances of the respective conductors will. This influence depends on the quality of the Winding of the current detection coils. Within the scope of the invention Can be the interfering influences of adjacent conductors Can be limited by the fact that, according to a method for producing the current detection coil according to claim 3, the feed of the ring core winding machine Constant and dimensioned in such a way that, Given the number of turns between the beginning and the end of the A gap of not more than 0,5% of the circumference of the Ring body.

The burr-free manufacture of the annular body of the current detection coil Can be achieved within the scope of the invention by a Device according to Claim 4, in which the partial joint of the Shape in the flattened area of ​​the cross-sectional shape of the Ring body. By this measure, a Wash the partial joint through the sprayed material and thus one Burr formation. Subsequent operations to the Removal of any burrs that may have occurred Either dispensable or limited to one Minimal effort.

The invention is described in more detail below with reference to the embodiment shown in FIGS Illustrated in more detail.

FIGS. 1 and 2 show an annular body as a carrier of a Current detection coil in plan view and in section.

FIG. 3 shows, in section, a part of a production line Of an annular body according to FIGS. 1 and 2 Injection mold.

An example of the arrangement of a current detection coil Show FIGS. 4 and 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 2, an annular body is shown, which as Carrier of a winding for a Rogowski principle Operating current transformer. The annular body 1 has a On the outer circumference and on the inner circumference The remaining contour being approximately semicircular Is. For producing the annular body 1, In FIG. 3, the partial joint 3 of which is shown in FIG Outer flattened area 4 and the inner flattened area Section 5 of the cross-sectional shape. The plastic syringe Of the annular body 1 is preferably provided with an annular groove Short glass fibers filled thermosetting resin mixture Polyester base. This gives annular bodies 1 with good dimensional stability, Strength against deformation as well as very low Thermal expansion under the influence of the forces occurring during operation Temperatures.

The beginning and the end of the force acting on the annular body 1 by means of the A winding 8 to be applied to a ring core winding machine Shown in FIG. As you can see, there is only one Very small gap 9 between the winding start and the winding end. For a given number of turns, this is achieved by constant And appropriately dimensioned feed of the used for the production Ring core winding machine. Through the whole of the Ring 1 equal distance of the turns and the As a percentage of the circumference of the ring body 1, is very high Small gap 9 can be mistakes as they are caused by a mutual Displacement of the magnetic fields of adjacent phases in A low-voltage circuit breaker can occur, only Minimally. As a result, the completed current detection coil is completed Able to measure a current range Which starts at a few A and reaches about 150 kA enough. In particular, the lower measuring limit is not only measured By the characteristics of the current detection coil, but Also by the characteristics of an electronic evaluation circuit To which the current detection coil Is to be connected. Therefore, starting at about 50 A with a Reliable current measurement.

Due to the position of the partial joint 3 in the regions 4 and 5 of the Ring body 1 (FIG. 2), there is only a slight inclination to the Burr formation during production. Should nevertheless ridge arise, It is advisable to replace it with a subsequent one Machining before using a ring core winding machine The provided winding is applied to the annular body 1 becomes. Should be the entire range of occurring currents Are detected by a single winding, the Winding have a large number of windings. Accordingly It is necessary to use a winding wire with very Small diameter. An annular body of, for example 100 mm outer diameter and a cross - section of About 8x12 mm can be used with about three thousand windings Copper wire of 0.07 mm thick.

A completed current detection coil 6 can be arranged in this manner As shown in FIGS. 4 and 5. These Has a housing open on one side 7, which has a central window 10 for the passage of a Shaped conductor of a circuit breaker. The annular elements, which are formed using the annular body 1 according to FIGS And 2 is located in FIG An annular space 11 of the housing 7, Potting compound 12 is attached and covered. The same potting compound 12 serves to establish an additional inductive Stomendler 13 including the potting compound 12 in the FIG. 5 is omitted. The current transformer 13 can, for example, Serve to provide an auxiliary energy which, Operation of a circuit to be connected to the current detection coil 6 Electronic evaluation circuit is required. Further An electronic trip unit can be operated by means of the current transformer 13 operate.