Shunt terminal type cement resistor

Abstract

The application provides a parallel terminal type cement resistor, and relates to the technical field of resistors, which comprises at least two parallel arranged alumina ceramic core rods, and resistance alloy wires are wound on the surfaces of the core rods; each of the core rods is connected with the same pair of resistance end pieces at both ends to form a parallel circuit; and the core rods and connecting pieces are integrally packaged in a cement body. The application can be used to manufacture a high-impact energy resistor, realize parallel connection of resistance core rods, improve the high-current resistance of the resistor, and pass a larger current. The application adopts a three-core rod "H" layout, so that the current distribution uniformity reaches 95%, and single path overload is avoided.

Description

Technical Field

[0001] This invention belongs to the field of resistor technology, specifically relating to a parallel terminal type cement resistor. Background Technology

[0002] Current mainstream cement resistors use a single ceramic core rod structure (such as talc ceramic, cordierite, etc.). Due to the limitation of core rod size, common models (such as 5W) have a size of 20×10×10mm. 3 Power density < 0.25 W / cm³ 3 It has the following defects:

[0003] Poor thermal conductivity; prone to localized overheating and burnout under high current.

[0004] The limited space for individual windings results in low power density.

[0005] The high resistance of the terminal connections limits the overload capacity.

[0006] In conclusion, providing an optimized resistor structure capable of handling larger currents is a pressing issue that needs to be addressed. Summary of the Invention

[0007] To address the problems of resistors with single ceramic core rod structures, this invention researches and develops a parallel terminal type cement resistor. By using a parallel connection, it can withstand greater current surges.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a parallel terminal type cement resistor, characterized in that it comprises:

[0009] At least two parallel alumina ceramic core rods, with resistance alloy wire wound on their surfaces;

[0010] Each of the core rods is connected to the same pair of resistor terminals at both ends, forming a parallel circuit;

[0011] The mandrel and connector are encapsulated in a cement body.

[0012] Specifically, in some embodiments, each of the core rods is fixed at both ends by a conductive iron cap, and a wire is welded to the outside of the iron cap to the resistor end piece.

[0013] Specifically, in some embodiments, the cement body is provided with a ceramic shell.

[0014] Specifically, in some embodiments, the alumina core rod has a purity of ≥99%, a thermal conductivity of ≥20W / m·K, and a core rod spacing of 1.2-1.5 times the rod diameter.

[0015] Specifically, in some embodiments, the pressing pressure between the iron cap and the mandrel is ≥5MPa, the pressing interface is filled with high-temperature resistant conductive adhesive, the contact resistance is ≤1mΩ, and the pressing edge is provided with a chamfer with a radius ≥0.8mm.

[0016] Specifically, in some embodiments, boron nitride particles are added before the cement slurry is injected, and the slurry is ultrasonically dispersed for 10 to 20 minutes to ensure uniformity.

[0017] Specifically, in some embodiments, during the iron cap crimping, a temperature gradient is used to apply pressure from the mandrel end at 300°C to the conductor end at 25°C, with the crimping force gradually decreasing from 8MPa to 5MPa.

[0018] Specifically, in some embodiments, a third vertically intersecting alumina core rod is also included, forming an "I" shape with the original two core rods, and the three core rod wires are connected to the resistor terminal piece.

[0019] Another embodiment of the present invention also provides a method for preparing the resistor, characterized by comprising the steps of:

[0020] The alumina core rod was annealed at 700-900℃ for 1 hour.

[0021] Resistance alloy wire is wound at a tension of 0.3–0.8 N using a tension-controlled winding machine;

[0022] The iron caps are hydraulically pressed onto both ends of the mandrel, and the conductive adhesive is then cured.

[0023] The wires are welded to the resistor terminals using a pulsed laser.

[0024] Cement grout was injected under vibration conditions, and the mixture was cured at 80°C for 24 hours after molding.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention adopts a parallel connection to produce high impact energy, realizes the parallel connection of the resistive core rod to improve the resistance of high current resistors, and can pass a larger current.

[0027] (2) The present invention adopts a three-core rod “I” layout to achieve a current distribution uniformity of 95% and avoid single-path overload. Attached Figure Description

[0028] Figure 1 This is a perspective view of the parallel terminal type cement resistor of the present invention.

[0029] Figure 2 This is a schematic diagram of the resistor terminal structure of the parallel terminal type cement resistor of the present invention.

[0030] Figure 3This is a schematic diagram of the parallel connection structure of the resistor terminal and the core rod of the present invention.

[0031] Figure 4 This is a schematic diagram of the overall structure of the present invention.

[0032] In the diagram: 1-Resistor terminal; 2-Resistor alloy wire; 3-Core rod; 4-Ceramic shell. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. In the following embodiments, all raw materials are known commercially available products.

[0034] Combination Figure 1-4 This invention provides a parallel terminal type cement resistor, comprising at least two parallel alumina ceramic core rods with resistance alloy wire wound on their surfaces;

[0035] Each of the core rods is connected to the same pair of resistor terminals at both ends, forming a parallel circuit;

[0036] The mandrel and connector are encapsulated in a cement body.

[0037] Specifically, in conjunction with 1-2, this embodiment uses two parallel core rods 3, with both ends connected to the same set of resistor terminals 1, and a resistance alloy wire 2 is wound on the surface of the alumina ceramic core rod 3.

[0038] Furthermore, the two ends of the core rod 3 are fixed by pressing with conductive iron caps, and wires are welded to the outside of the iron caps to the resistor terminals. The pressing pressure between the iron caps and the core rod is ≥5MPa, the pressing interface is filled with high-temperature resistant conductive adhesive, the contact resistance is ≤1mΩ, and the pressing edge has a chamfer with a radius ≥0.8mm. Using the above scheme, stable contact resistance can be guaranteed, the iron caps do not loosen during 50G random vibration testing, and high tensile strength is achieved. The conductive adhesive (such as Ag-filled epoxy resin) can flow and fill the nanoscale gaps at the pressing interface, improving the uniformity of current distribution by 40%, avoiding local overheating, and effectively absorbing the stress generated by thermal expansion differences, reducing interface cracks by 90% after thermal cycling.

[0039] Furthermore, the alumina core rod has a purity ≥99%, a thermal conductivity ≥20 W / m·K, and a core rod spacing of 1.2-1.5 times the rod diameter. The bending strength of 99% pure alumina is 380-400 MPa (approximately 250 MPa for 95% purity), and the breakage rate during iron cap pressing decreases from 5% to 0.1%. This alumina core rod exhibits high lattice integrity and unobstructed heat conduction paths. The measured thermal conductivity reaches 25-35 W / m·K (compared to only 15 W / m·K for low-purity 95% Al2O3), resulting in a 40% faster transient thermal response and preventing thermal conductivity degradation after long-term use.

[0040] Furthermore, during the iron cap crimping, a temperature gradient is applied, with the mandrel end at 300°C and the conductor end at 25°C, gradually reducing the crimping force from 8 MPa to 5 MPa. The specific steps are as follows:

[0041] Preheating phase:

[0042] The mandrel end (crimping area) is induction heated to 300±10℃ (alumina has a thermal expansion coefficient of 8.5×10). -6 / ℃);

[0043] Keep the wire end (soldering area) at 25±5℃ (to avoid pre-melting of the solder).

[0044] Gradient pressurization phase:

[0045] Initial pressure: Apply 8MPa to the end of the mandrel using a multi-segment hydraulic press for 5 seconds to make the iron cap initially adhere to the high-temperature mandrel;

[0046] Pressure transition: linearly decreases to 5 MPa at the lead wire end within 10 seconds, forming a pressure gradient;

[0047] Pressure holding and curing: Maintain a pressure of 5 MPa for 60 seconds to cure the conductive adhesive (Ag epoxy resin).

[0048] Cooling phase:

[0049] Depressurize after natural cooling to 80°C to avoid stress concentration caused by sudden cooling.

[0050] By employing a gradient pressurization method, the expansion difference between the mandrel end and the cap end is only 0.4μm, almost eliminating the initial stress of cold pressing. High plasticity is maintained in the low-temperature region, preventing conductor crushing. The pressure gradient (8→5MPa) causes the stress distribution to decrease from the mandrel end to the conductor end, reducing the peak residual stress. This temperature-pressure dual-gradient design reduces the interfacial residual stress from 185MPa to 85MPa, significantly improving device lifespan.

[0051] Furthermore, during the cement encapsulation process, boron nitride particles need to be added before the cement slurry is injected, and ultrasonic dispersion for 10–20 minutes is used to ensure uniformity. A 95% alumina ceramic shell (1.5 mm thick) is then added to the cement body to enhance mechanical strength.

[0052] In another embodiment of the present invention, a third vertically intersecting alumina core rod is also included, which is arranged in an "I" shape with the original two core rods. The three core rods are connected to the resistor terminal piece. The addition of the vertical core rod, which is arranged in an "I" shape with the two core rods, and whose wires are connected to the terminal piece, significantly improves the uniformity of current distribution, reduces branch current deviation, and improves instantaneous current withstand performance. Under a 1200A / 50ms pulse, the maximum temperature is only 110℃.

[0053] Furthermore, embodiments of the present invention also provide a method for fabricating a resistor, comprising the following steps:

[0054] The alumina core rod was annealed at 700-900℃ for 1 hour.

[0055] Resistance alloy wire is wound at a tension of 0.3–0.8 N using a tension-controlled winding machine;

[0056] The iron caps are hydraulically pressed onto both ends of the mandrel, and the conductive adhesive is then cured.

[0057] The wires are welded to the resistor terminals using a pulsed laser.

[0058] Cement grout was injected under vibration conditions, and the mixture was cured at 80°C for 24 hours after molding.

[0059] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A cement resistor of the parallel terminal type, characterized by, include: At least two parallel alumina ceramic core rods, with resistance alloy wire wound on their surfaces; Each of the alumina ceramic core rods is connected to the same pair of resistor terminals at both ends to form a parallel circuit; The alumina ceramic core rod and the connector are integrally encapsulated in a cement body; Each alumina ceramic core rod is fixed at both ends by a conductive iron cap, and a wire is welded to the outside of the iron cap to the resistor end piece; The alumina ceramic core rod has a purity of ≥99%, a thermal conductivity of ≥20 W / m·K, and the spacing between the alumina ceramic core rods is 1.2-1.5 times the rod diameter. The pressing pressure between the iron cap and the alumina ceramic core rod is ≥5MPa, the pressing interface is filled with high temperature resistant conductive adhesive, the contact resistance is ≤1mΩ, and the pressing edge is provided with a chamfer with a radius ≥0.8mm. Before the cement is injected, boron nitride particles need to be added and ultrasonically dispersed for 10-20 minutes to ensure uniformity. When crimping the iron cap, a temperature gradient is used to apply pressure from the alumina ceramic core rod end 300℃ to the wire end 25℃, and the crimping force is gradually reduced from 8MPa to 5MPa. It also includes a third vertically intersecting alumina ceramic core rod, which forms an "I" shape with the original two core rods, and the three core rod wires are connected to the resistor terminals.

2. The cement resistor of claim 1, wherein The cement body is covered with a ceramic shell.

3. A method of manufacturing a resistor as claimed in claim 1 or 2, characterized in that, Including the following steps: The alumina ceramic core rod was annealed at 700~900℃ for 1 hour. Resistance alloy wire is wound with a tension control winding machine at a tension of 0.3~0.8N; The iron caps are hydraulically pressed onto both ends of the alumina ceramic core rod, and the conductive adhesive is then cured. The wires are welded to the resistor terminals using a pulsed laser. Cement grout was injected under vibration conditions, and the mixture was cured at 80°C for 24 hours after molding.

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