RU176289U1 - ELECTRIC POLE OF THE CIRCUIT BREAKER - Google Patents

Abstract

The utility model relates to electrical engineering, namely to the electrical poles of circuit breakers with current transformers in the main circuit. The technical result consists in reducing the dimensions of the pole and reducing the influence of external magnetic fields on the measurement error of short circuit currents. A pole of a circuit breaker is proposed, comprising a housing, an upper terminal with contacts, a lower terminal connected by flexible connections with lamellas on which movable contacts are mounted, a rotary bracket with lamellas interacting with a switch mechanism, a current transformer in the form of a rectangular core with coils mounted on the lower conclusion. The current transformer is made with a variable cross section of the magnetic circuit. From the side of the angular connections of the current lead, the core has a twice as large cross section. In addition, local shielding was applied with massive burnt pads of open sections of the magnetic circuit and the ends of the coil. Ease of assembly of the core with overlays and mounting of the transformer in the pole is ensured. 6 ill.

Description

The proposed utility model relates to electrical engineering, namely to the poles of low-voltage circuit breakers for high currents with current transformers in the main circuit of the switch.

Known power multi-pole circuit breakers for currents 630-6300 A, containing in each pole a current transformer for measuring overload currents and short circuit currents, which serves as a sensor for the electronic control circuit of the circuit breaker in emergency conditions [1-4]. Currently, despite the use of current sensors on other operating principles (resistive shunt, Rogowski coil, Hall sensor, magneto-optical sensor), electromagnetic current transformers [5], designed for operation in transient conditions, have their preferred applications, defined by such qualities transformers, such as simplicity, high reliability, high power output, resistance to special effects [6]. The use and improvement of current transformers at the poles of circuit breakers in combination with the increased capabilities of electronic overcurrent releases has led to the expansion of the functionality of circuit breakers in terms of expanding ranges of disconnected currents and time delays with various functional dependences of time delays on the value of the current being switched off, as well as in terms of improving accuracy disconnecting currents. The conditions were created for constructing selective consumer protection systems, both in current and in terms of tripping by using selective circuit breakers combined in a single circuit in accordance with their ability to coordinate disconnected currents. The main problem of using current transformers in the poles of circuit breakers is to ensure the corresponding measurement error of short-circuit currents, on the one hand, and to ensure the minimum size of the circuit-breaker pole, on the other hand. Thus, according to the standard [7], circuit breakers specially designed to provide selectivity under short-circuit conditions with respect to other short-circuit protection devices must have a rated short-time withstand current of at least 12 rated currents at rated circuit breaker currents of up to 2500 A and at least 30 kA , at rated currents over 2500 A. Current transformers, as a minimum, must work in these current ranges and carry out measurements with a given error. Placing the transformer in the pole of the switch should not significantly increase the dimensions of the pole and should exclude the influence of magnetic fields from the main circuit of the switch on the measurement error of short-circuit currents. Methods for ensuring the required error in measuring currents, including in transient modes, have been sufficiently studied and covered in sources [6, 8]. However, the influence of external magnetic fields on the measurement error from different sections of the current lead of the main circuit of the pole (for different current lead configurations and different positions of the current transformer relative to the current lead sections) is determined mainly experimentally on mock-up product samples, due to the complexity of compiling mathematical models taking into account many factors , as well as low accuracy of calculations [8]. It is especially important to reduce the influence of external magnetic fields on the configuration of the own circuit of the pole, which is designed with minimal dimensions in height and depth of the switch to obtain the competitive advantages of the circuit breaker. To reduce the dimensions of the pole, the developer has to change the rectilinear conductor into a combination of L-shaped and U-shaped turns, creating, as you know, magnetic fields, which, when the current transformer is located close to it, can degrade the accuracy of measurements of short-circuit currents and lead to false tripping of the circuit breaker. A radical way to reduce the influence of powerful magnetic fields is to completely shield the source of the field (current path, bus) or to completely shield the protected object (current transformer) [9]. In most cases, the limited space of the pole of the circuit breaker and the impossibility of increasing it is a key factor in the impossibility of complete shielding of both the current lead and the current transformer. The limited layout space of the pole also makes it difficult to maintain tolerances between the current transformer and the current lead. This inevitably leads to an increase in the influence of the shape of the pole conductor on the accuracy of the transformer measuring the primary current, especially at high multiples of short circuit currents. The listed problems are to a greater or lesser extent characteristic of all the analogues cited in the sources [2-4].

The prototype of the claimed utility model in technical essence is the pole of the switch according to the patent [2]. The prototype, (see Fig. 2, 8, 11 and 14 in the description of the patent [2]), contains the upper terminal 44 (Fig. 2) with stationary workers 32 and arcing 156 (Fig. 8) contacts, the lower terminal 53, connected by flexible connections 118 with lamellae 114, 148 (Fig. 11), on which movable workers 34 and arrester 116 contacts are mounted. The pole also has a swivel bracket 132, which carries spring-loaded slats 114, 148 and interacts with the switch mechanism, a current transformer 264 (Fig. 2, 14) mounted on the bus 46 of the lower terminal 53 and made in the form of a rectangular core 269 with coils 54, placed on the long sides of the core. With a decrease in the height of the pole due to the approach of the lower terminal 53 to the current transformer 264, the magnetic field pickup will increase from the angular connection of the terminal 53 with the bus 46 passing through the core 269, which will lead to errors in the measurement of short circuit currents. With an increase in the multiplicity of short-circuit currents with an unchanged design, the pickups from the mentioned angular connection will also increase, which will limit the expansion of the range of current settings. This is due to the selected core configuration of the transformer. Thus, the prototype is limited in its ability to reduce the height of the pole and the ability to provide a given error in measuring current when increasing disconnected short-circuit currents.

The proposed utility model has the following objectives:

- reducing the height and depth of the pole of the switch while maintaining the current transformer of a given accuracy of measuring currents in the main circuit of the pole;

- reducing the influence of external magnetic fields on the measurement error of short circuit currents and eliminating false positives of the circuit breaker;

- simplification of the assembly and installation of the current transformer in the pole of the switch.

The goals are achieved by the fact that in the pole of the circuit breaker containing the housing, the upper terminal with fixed working and arcing contacts, the lower terminal connected by U-shaped flexible connections with lamellas, on which the movable working and arcing contacts are mounted, a rotary bracket carrying on a spring-loaded lamellas and a current transformer made in the form of a rectangular core with coils placed on the long sides of the core and interacting with the switch mechanism, ted on the lower terminal of the first short side of the upper narrow side output and the second short side - at the bottom narrow side of the output transformer core is in the form of a laminated magnetic circuit with variable section. The rectangular core is made in such a way that its first short side above the terminal opposite the flexible connections is at least twice as wide (section) as the width (section) of the second short side below the terminal. In addition, the core is equipped with two wide and two narrow overlays of lined ferromagnetic material having areas corresponding to the areas of the first and second short sides of the core. The pads are mounted in pairs on both sides of the core so that the end surfaces of the pads and the core coincide. Moreover, the thickness of the pads is chosen not less than the size of the protruding part of the coils. The inner end surfaces of the pads are adjacent to the protruding ends of the coils. In this case, the pads are fixed on both sides of the core with four cheeks and screws made of soft magnetic material, and two cheeks located on the side of the pole housing have consoles with holes protruding beyond the dimensions of the core.

The implementation of the core with an enlarged cross section of its first short side above the lower terminal opposite the L-shaped connection with U-shaped flexible connections is at least two times larger than the cross section of the second short side under the terminal, which reduced the degree of saturation of the magnetic circuit from the effects of induced short-term magnetic fields arising from the passage of short-circuit currents along an indirect linear main circuit having L-shaped U-shaped sections. The supply of the short sides of the core with two wide and two narrow overlays of burdened ferromagnetic material, having areas corresponding to the areas of the first and second short sides of the core, creates local screens that protect the transformer from the penetration of external powerful magnetic fields coming both from its own pole circuit and from circuits of adjacent poles during the passage of short circuit currents. Since the pads are mounted in pairs on both sides of the core so that the end surfaces of the pads and the core coincide, and the thickness of the pads is chosen not less than the size of the protruding part of the coils and the inner end surfaces of the pads are adjacent to the protruding ends of the coils, the pads partially shield the transformer coils. This design reduces the influence of external magnetic fields on the measurement errors of short-circuit currents while increasing the multiplicity of disconnected short-circuit currents, thereby eliminating false tripping of the circuit breaker. Reducing the influence of external magnetic fields on the measurement errors of currents due to an increase in the cross section of the magnetic circuit from the side of penetration of this field and due to partial shielding with massive lined overlays, reduces the distance between the current transformer and the radiating sections of the current lead, which reduces the functional dimensions of the electric pole and, ultimately , height and depth of the circuit breaker. To simplify the assembly of the transformer, both the lined core and lined linings are fastened together by a single set of fasteners, consisting of four cheeks and screws of soft magnetic material, and to simplify the installation of the transformer in the pole of the switch, two cheeks located on the side of the pole body have consoles with holes protruding for the dimensions of the core.

The proposed utility model can be used as a small-sized electric pole with an electromagnetic current transformer in mass production as part of multi-pole low-voltage circuit breakers for large rated currents of 630-6300 A with a large multiplicity of disconnected short-circuit currents. Due to the proposed design of a rectangular core with an enlarged cross section of one of its short sides and supplying the short sides of the core with two pairs of thick laminated pads, the influence of external fields on the measurement error of currents is reduced, which, on the one hand, allows to reduce the dimensions of the circuit breaker, and on the other, to increase multiplicity of disconnected currents without false trips of the switch.

The analysis of the prior art by the applicant, including a search by patents and scientific and technical sources of information and identification of sources containing information about analogues of the claimed utility model, allowed to establish that the applicant did not find a prototype characterized by features identical to all the essential features of the claimed utility model. The determination from the list of identified analogues of the prototype as the closest in terms of the set of essential features of the analogue made it possible to identify the set of significant distinguishing features in relation to the applicant’s perceived technical result in the claimed design set forth in the utility model formula.

Therefore, the claimed utility model meets the condition of "novelty."

The design of the claimed utility model is depicted in FIG. 1-6. In FIG. 1 shows a side view of the electrical pole of a circuit breaker. In FIG. Figure 2 shows the same side view of the pole, but with the arrows showing the direction of the current along the current path of the pole. The housing and the pole bracket are conventionally not shown here. The letters denote the critical, in terms of electromagnetic interference to the transformer, distances to the current lead. In FIG. Figure 3 is a view A from the rear of the pole with a conditionally not shown housing. FIG. 4, 5, 6 give an idea of the design of the core of the current transformer on an enlarged scale. In FIG. 4 is a plan view of the core; FIG. Figure 5 shows a section B-B with a conventionally spaced lined core, lined plates and cheeks made of solid material. FIG. 6 shows in a perspective view the composition of the transformer core, the shape of the core plates, the shape of the plates of the overlays and cheeks and gives an idea of the assembly order of the core. The transformer coils are not conventionally shown here.

The electric pole of the circuit breaker (see Fig. 1 - 3) contains mounted on the housing 1, the upper terminal 2 with fixed workers 3 and arcing 4 contacts, the lower terminal 5, connected via U-shaped flexible connections 6 with lamellas 7, 8, on of which movable workers 9 and arrester 10 contacts are installed, a swivel bracket 11 carrying spring-loaded slats 7, 8 and interacting with a switch mechanism (mechanism not shown). The current transformer 12 is made in the form of a rectangular core 13 (see in Fig. 3) with coils 14-17 placed on the long sides 18, 19 (see in Fig. 4) of the core 13. The current transformer 12 is mounted on the lower terminal 5 so that the first short side 20 of the core 13 is located above the upper narrow side 21 of the output 5, and the second short side 22 under the lower narrow side 23 of the output 5. The core 13 of the transformer is made in the form of a burnt magnetic circuit with a variable cross-section. The rectangular core 13 (see Fig. 4) is made in such a way that its first short 20 side above terminal 5 (see Fig. 3) opposite the joints with U-shaped flexible connections 6 has at least at least twice as large the width (section) than the width (section) of the second short side 22 under the terminal 5 (see Fig. 5). In addition, the core is equipped with two wide 24, 25 and two narrow 26, 27 overlays of lined ferromagnetic material, having areas corresponding to the areas of the first 20 and second 22 short sides of the core 13. The overlays 24, 25 and 26, 27 are mounted in pairs on both sides core so that the end surfaces 28, 29 and 30, 31 of the pads 24, 25 and 26, 27 coincide with the end surfaces 32, 33 of the core. Moreover, the thickness t of all the pads 24-27 is chosen not less than the size h (see in Fig. 2) of the protruding part of the coils 14-17. The inner end surfaces 34-37 of the pads 24-27 are adjacent to the protruding ends 38-41 of the coils 14-17. While the pads 24-27 are fixed on both sides of the core 13 with four cheeks 42-45 and screws 46 made of soft magnetic material, and two cheeks 43, 45 located on the side of the pole housing 1 have consoles 47, 48 and 49, 50 with an opening 51 protruding beyond the dimensions of the core. Each core layer 13 is assembled from plates 52, 53 of FIG. 6, and wide overlays 24, 25 from plates 54, narrow overlays 26, 27 from plates 55.

The electric pole of the circuit breaker operates as follows. When rated currents flow through the pole from terminal 2 to terminal 5 (the current path I through the current path is indicated by arrows, see Fig. 2), the contacts of the pole 3, 9 and 4, 10 are closed. The current transformer, with the primary winding in the form of a bus of the lower terminal 5, in the secondary winding, consisting of coils 14-17, has a current proportional to the rated current of the circuit. The current of the secondary winding of the transformer serves as the control for the electronic circuit of the maximum release (in the drawings, the release and the mechanism of free trip are not shown). When a short-circuit current occurs in a circuit protected by a pole, the value of which exceeds a predetermined limit value of the trip current (set by the setting of the maximum release), a secondary current of the corresponding magnitude appears in the current transformer winding, which activates an automatic trip mechanism using an electronic release, which automatically opens pins 3, 9 and 4, 10 poles. With large current multiplicities (large ratios of short circuit current to rated pole current) due to the limited functional dimensions of the pole (height V _f , depth G _f , see Fig. 1) and the configuration of the pole conductor having L-shaped and U- shaped connections, the magnitude of the error measured by the primary current transformer begins to be influenced by electromagnetic fields emanating from problem angular joints, determined approximately by the sizes B, D, E, D, G relative to the axis of the core 13 of the transformer 12 (see Fig. 2). When the measurement error exceeds the limits set by the standard, false trips of the switch pole begin, which makes it necessary to reduce the multiplicity of the disconnected currents, i.e., to worsen the technical characteristics of the product. It was experimentally established that the most effective measures to reduce the influence of external fields on the measurement errors of the primary currents are to increase the core section 13 from the side of the L-shaped joints at least twice, i.e. increasing the width of the upper short side 20 as compared with the width of the lower side 22. Also helps to reduce measurement errors by local shielding of open core sections on its narrow sides 20, 22 and the ends of the coils 14-17 by massive lamellas of iron 24-27 in the form of plates 54, 55. Theoretically, it is not possible to determine the size of the increase in the width of the short side 20 of the core 13, as well as the thickness of the plates 24-27 due to the complex configuration of the current lead and the need to take into account a large number external factors, including the frequency spectrum of the radiating field in transient conditions. Therefore, at given nominal currents and short circuit currents, the sizes are selected experimentally during research tests. Reducing the measurement error of short-circuit currents in the proposed pole using the proposed tools allows to reduce the critical distances B, D, E, D, G, and therefore reduce the functional dimensions (height B _f and depth G _f ) of the pole, which ultimately allows to reduce and dimensions of the circuit breaker. The implementation of the core 13 in the form of a magnetic circuit with different cross sections of its short sides 20, 22, local shielding using pads 24-27 reduce the influence of external magnetic fields on the measurement error of short circuit currents and eliminate false tripping of the circuit breaker. The combined fastening of the plates 52, 53 of the core and the plates 54, 55 of the plates 24-27 using single cheeks 42-45 and screws 46 simplifies the assembly of the transformer 12. And the implementation of the cheeks 43, with consoles 47-50 extending beyond the dimensions of the core, simplifies the installation of the transformer on the housing 1 pole.

Thus, the implementation of the electric pole of a circuit breaker with an electromagnetic current transformer in the claimed form with the described distinguishing features, namely:

- with the core 13 of the transformer 12 in the form of a magnetic circuit with a variable cross section laden from the plates 52, 53;

- with an increased, not less than two times the width of the first short side 20 of the core compared with the width of the second short side 22;

- with two lined wide 24, 25 and two narrow 26, 27 plates of plates 54, 55 mounted on the core in the described relationship and relative position in relation to other elements of the transformer and the pole;

- with common linings 42-45 for fixing the core, linings and mounting the transformer,

allowed to achieve the goals of the claimed utility model.

The described design of the utility model and the description of its operation indicate the compliance of the claimed utility model with the following set of conditions:

- the device embodying the claimed model, when implemented, is intended for use in multipolar circuit breakers for large, up to 6300 A, currents and relates to electrical engineering, namely to the electric poles of circuit breakers;

- for the claimed design in the form as described in the stated utility model formula, the possibility of its implementation using the means described in the application is confirmed;

- a device embodying the claimed utility model, when implemented, is capable of ensuring the achievement of the technical result perceived by the applicant.

Prototypes of the inventive electric pole were manufactured and tested with positive results in the composition of multi-pole circuit breakers for high currents.

Therefore, the claimed utility model meets the condition of "industrial applicability".

Information sources

1. Description of the patent CN 205248211 U, H01H 71/02, publ. 05/18/2016.

2. Description of the patent US 4891618, H01H 77/10, publ. 01/02/1990.

3. AWB 1230-1605. Instruction “Operation and maintenance of low-voltage circuit breakers IZM”, p. 21, fig. 22. (IZM circuit breakers for currents up to 6300 A. Instrument catalog MOELLER. 2005).

4. ABB SACE catalog. Emax. Low-voltage circuit breakers for rated currents 800-6300 A. Design features, p. 1/8.

5. Description of the patent for the invention SU 771738, H01F 38/30, publ. 10/15/1980.

6. Romaniuk F.A., Tishechkin A.A., Rumyantsev V.Yu., Novash I.V., Bobko N.N., Glinsky E.V. "The effect of saturation of current transformers on the operation of current protection." The journal "Energy". Proceedings of higher educational institutions and energy associations of the CIS, issue No. 1, 2010, p. 5-9.

7. GOST R 50030.2-2010 Low-voltage distribution and control equipment, part 2. Circuit breakers. Date of introduction 01.01.2012.

8. Afanasyev V.V., Adonyev N.M., Kibel V.M., Orphan I.M., Stogniy B.S. Current transformers. Energoatomizdat, Leningrad Branch, 1989.

9. Wolf Homm. "Elimination of the influence of magnetic fields in electric meters with pulse transformers." Components and Technologies Magazine, No. 3, 2013, p. 142-148.

Claims (1)

The electric pole of the circuit breaker, comprising a housing, an upper terminal with fixed working and arcing contacts, a lower terminal connected by U-shaped flexible connections with lamellas, on which movable working and arcing contacts are installed, a rotary bracket carrying spring-loaded lamellas and interacting with by a switch mechanism, a current transformer made in the form of a rectangular core with coils placed on the long sides of the core, and mounted on the lower terminal e the first short side above the upper narrow side of the output, and the second short side under the lower narrow side of the output, characterized in that the core of the transformer is made in the form of a charged magnetic core with a variable cross-section so that the first short side of the core above the output opposite the connections with flexible connections has at least at least twice the width than the width of the second short side under the output, in addition, the core is equipped with two wide and two narrow lining of lined fer of magnetic material having areas correspondingly equal to the areas of the first and second short sides of the core and mounted on both sides of the core so that the end surfaces of the plates and the core coincide, and the thickness of the plates is chosen not less than the size of the protruding part of the coils, and the inner end surfaces of the plates adjoin protruding ends of the coils, while the pads are fixed on both sides of the core with four cheeks and screws made of soft magnetic material, and two cheeks located with side of the pole housing are console with holes extending beyond the core dimensions.

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