Extra-high voltage resistor with through hole lead structure suitable for oil immersion working condition

Abstract

The utility model discloses an extra-high voltage resistor with a through hole lead structure suitable for an oil immersion working condition, and belongs to the technical field of resistors. The resistor comprises a ceramic substrate, the thickness of the ceramic substrate is 2 mm, and circular lead through holes are symmetrically formed in the two ends of the ceramic substrate; a lead penetrates through the circular lead through hole, a nail head is arranged at the front end of the lead, and the nail head and the ceramic substrate form mechanical limiting fit; silver electrode layers are printed on the two end faces of the ceramic substrate and extend to the periphery of the circular lead through hole, and the lead and the silver electrode layers are welded and fixed; a snakelike resistance tape is printed on the surface of the ceramic substrate, and two ends of the snakelike resistance tape are conductively connected with the silver electrode layer; the surfaces of the snakelike resistance tape and the silver electrode layer are covered with an encapsulation film, and the encapsulation film is a benzyl toluene resistant organic material dielectric film coating. The resistor disclosed by the utility model is reasonable in structural design and can better adapt to an extra-high-voltage benzyl toluene oil immersion working condition.

Description

Technical Field

[0001] This utility model relates to the field of resistor technology, and more specifically, to an ultra-high voltage resistor with a through-hole lead structure suitable for oil immersion conditions. Background Technology

[0002] While existing chip-type glass-glazed UHV resistors boast compact structures and mature manufacturing processes, they still exhibit several shortcomings under long-term high-voltage and oil-immersion conditions. Firstly, existing chip-type glass-glazed UHV resistors generally utilize ceramic substrates approximately 1mm thick, resulting in insufficient dielectric strength. This makes them prone to punch-through breakdown or surface flashover under UHV oil-immersion electric fields (the oil immersion environment exacerbates the electric field concentration effect), limiting their application in UHV oil-immersion systems. Secondly, traditional end structures often employ planar electrodes or silver-plated end face welding methods. These result in small weld area and low mechanical strength, making them susceptible to detachment under vibration, temperature cycling, and oil erosion in UHV oil-immersion systems, leading to increased contact resistance and electrical failure. Furthermore, traditional electrodes are often rectangular / right-angled structures with unoptimized edge design, easily forming electric field concentration and further increasing the risk of end discharge. Additionally, the resistive film patterns of existing resistors are often uniformly pitched serpentine, resulting in concentrated electric field distribution and limited creepage distance. This fails to effectively disperse voltage gradients, making them prone to partial discharge under impact or pulse voltage conditions, and the oil immersion environment further amplifies this risk. Finally, traditional surface encapsulation materials (mostly ordinary inorganic films or resin coatings) are mostly used in air or resin encapsulation environments. They have poor chemical compatibility with benzyltoluene insulating oil commonly used in ultra-high voltage systems. During long-term operation, they are prone to swelling, oxidation, or ion migration, which leads to resistance drift and shortened lifespan. At the same time, traditional electrodes use ordinary conductive pastes, which are prone to delamination due to thermal shock in oil immersion high-temperature environments, affecting the stability of electrical connections.

[0003] In view of this, this utility model proposes an ultra-high voltage resistor with a through-hole lead structure suitable for oil immersion conditions. Utility Model Content

[0004] The purpose of this invention is to provide an ultra-high voltage resistor with a through-hole lead structure suitable for oil immersion conditions, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A high-voltage resistor with through-hole lead structure suitable for oil immersion conditions includes a ceramic substrate with a thickness of 2mm and circular lead through holes symmetrically arranged at both ends.

[0007] A lead wire is inserted into the circular lead wire through hole, and a nail head is provided at the front end of the lead wire. The nail head forms a mechanical limiting fit with the ceramic substrate.

[0008] Silver electrode layers are printed on both ends of the ceramic substrate, extending to the periphery of the circular lead through-hole, and the lead is welded and fixed to the silver electrode layer.

[0009] A serpentine resistance band is printed on the surface of the ceramic substrate, and the two ends of the serpentine resistance band are electrically connected to the silver electrode layer;

[0010] The surfaces of the serpentine resistor strip and the silver electrode layer are covered with an encapsulation film, which is an organic dielectric film coating resistant to benzyltoluene.

[0011] Preferably, the ceramic substrate is an alumina ceramic substrate, and its dielectric strength in an oil immersion environment is 10~12kV / mm.

[0012] Preferably, the nail head has a T-shaped or disc-shaped structure.

[0013] Preferably, the silver electrode layer is formed by high-temperature sintering of silver-palladium alloy conductive paste, and its edges are designed with rounded corners. The shape of the silver electrode layer is trapezoidal, rectangular, arc-shaped, serrated, or a combination of trapezoidal and arc-shaped.

[0014] Preferably, when the silver electrode layer is trapezoidal, its bottom edge faces the interior of the ceramic substrate, and its top edge is close to the circular lead hole.

[0015] Preferably, the width of the serpentine resistor strip is 0.5mm to 2mm, the spacing between adjacent rails is 1.5mm to 2.5mm, and the height of the rail is 16mm to 18mm.

[0016] Preferably, the encapsulating film is in the form of a glass glaze and has a thickness of 0.3 mm to 0.8 mm.

[0017] Preferably, the ceramic substrate surface is further provided with a resistance value mark, and the resistance value mark and the encapsulation film are located on different surfaces of the ceramic substrate or the encapsulation film covers the outside of the resistance value mark.

[0018] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0019] This utility model discloses a chip glass glaze ultra-high voltage resistor with trapezoidal electrodes and a benzyl toluene-resistant encapsulation layer. Its structural design is reasonable, and its parameters are clearly optimized, enabling it to better adapt to ultra-high voltage benzyl toluene oil immersion conditions. It offers the following advantages in terms of withstand voltage performance, mechanical reliability, and long-term stability:

[0020] 1. Insulation withstand voltage capability is significantly improved.

[0021] This invention employs a 2mm thick ceramic substrate, doubling the dielectric thickness compared to a conventional 1mm thick substrate, providing a higher breakthrough and breakdown margin under the same electric field strength. Simultaneously, combined with optimized geometric parameters of the serpentine resistor strip (preferably a rail width of 0.5–2mm, an adjacent rail spacing of 1.5–2.5mm, and a rail height of 16–18mm, along with a serpentine structure of seven peaks and six troughs), the equivalent conductive path and surface creepage distance are significantly extended within a limited chip area, resulting in a smoother voltage gradient distribution along the resistor strip. Single-variable test results show that within the above parameter range, the surface withstand voltage level of the sample is significantly higher than other parameter combinations, and no flashover or breakdown failure occurs, thus effectively improving the insulation safety margin of the resistor in ultra-high voltage oil-immersion environments.

[0022] 2. The electric and thermal fields are uniformly distributed, resulting in lower operating temperature rise and resistance drift.

[0023] This invention determined a reasonable ratio between the guide rail width, the spacing between adjacent guide rails, and the guide rail height through individual parameter optimization experiments. When the guide rail width is within the range of 0.5mm to 2mm, the conductor cross-sectional area and current density are reasonably matched, avoiding both local overheating and process defects caused by excessively narrow line widths, and path shortening and electric field concentration caused by excessively wide line widths. When the spacing between adjacent guide rails is within the range of 1.5mm to 2.5mm, the electric field lines are evenly distributed between adjacent conductive branches, avoiding both the problem of high field strength in narrow gaps and potential abrupt changes due to excessive spacing. When the guide rail height is within the range of 16mm to 18mm, the serpentine spread matches the effective area of ​​the substrate, and the path length and bending degree are moderate, which is conducive to the uniform distribution of potential and heat. The experimental results show that the sample with the above parameter combination has a low temperature rise, uniform heat distribution, and the resistance drift after 1000 hours of oil immersion aging remains within a small range, demonstrating good long-term stability.

[0024] 3. Reliable lead wire connection and high mechanical strength

[0025] This invention features circular lead-through holes at both ends of a ceramic substrate. A nail-headed lead is inserted through the holes and welded to a silver electrode. This design allows the lead to achieve electrical conductivity while simultaneously providing mechanical restraint through the engagement of the nail head and the through-hole, creating a dual-fixation structure of "welding + clamping." This structure effectively disperses mechanical and thermal stress at the lead, significantly improving the lead solder joints' resistance to pull-out and fatigue under oil immersion vibration and temperature cycling conditions. It also reduces the risk of poor contact and electrical failure caused by solder joint cracking and lead loosening, thereby enhancing the mechanical reliability of the device.

[0026] 4. Trapezoidal silver electrodes suppress end electric field concentration and improve the welding interface.

[0027] The silver electrode of this invention adopts a trapezoidal structure, with the short side facing inwards towards the resistance band and the long side close to the lead via. Compared with traditional rectangular or right-angled electrodes, the trapezoidal electrode has a gradually narrowing bevel at the edge, making the potential change during the transition of the electric field from the electrode region to the resistance band and encapsulation layer smoother. This helps to reduce the electric field concentration effect at the electrode edge and turning points, and suppresses surface discharge at the end. At the same time, the trapezoidal electrode has a larger welding area on the side near the via, resulting in a more complete interface between the solder and the electrode. This effectively disperses the current density and thermal stress at the solder joint, improving the reliability and resistance to electrochemical corrosion of the welded area.

[0028] 5. The benzyltoluene-resistant encapsulation structure significantly improves long-term stability under oil immersion conditions.

[0029] After the resistor is formed and sintered, this invention prints a benzyltoluene-resistant inorganic silicon-oxygen composite encapsulation film on the surface of the resistor strip and silver electrode, with a preferred thickness of 0.3–0.8 mm. This encapsulation layer forms a dense interface with the glass glaze resistor film and silver electrode, effectively blocking the penetration and erosion of benzyltoluene molecules and their oxidation byproducts into the resistor film and electrode, inhibiting chemical corrosion, swelling, and ion migration under high-temperature oil immersion conditions, and preventing the formation of leakage channels on the surface. Verification by long-term high-temperature aging tests in benzyltoluene oil shows that samples using this encapsulation structure exhibit minimal resistance drift, no obvious oxidation, cracks, or delamination on the surface, demonstrating good oil chemical stability and insulation reliability. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0031] Figure 2 This is a schematic diagram of the lead wire structure of this utility model.

[0032] The labels in the diagram are as follows: 1. Lead wire; 2. Ceramic substrate; 3. Encapsulation film; 4. Resistance value marking; 5. Serpentine resistor strip; 6. Silver electrode layer; 7. Circular lead through-hole; 11. Nail head. Detailed Implementation

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0034] Example:

[0035] Please see Figure 1-2A high-voltage resistor with a through-hole lead structure suitable for oil immersion applications includes a ceramic substrate 2 with a thickness of 2 mm, exhibiting higher mechanical strength and dielectric breakdown strength. Symmetrically arranged circular through-holes 7 at both ends allow for the insertion of leads 1 and the establishment of electrical and mechanical connections. The ceramic substrate 2 is an alumina ceramic substrate with a dielectric strength of 10~12 kV / mm in an oil immersion environment.

[0036] The ceramic substrate 2 has an increased insulation thickness compared to conventional chip resistor substrates, which significantly improves the dielectric breakdown voltage and surface creepage distance. Alumina ceramics have a dielectric strength of 10~12kV / mm in an oil-immersed environment; increasing the thickness by 1mm provides an additional 10~12kV breakdown margin, effectively preventing dielectric punch-through failure in ultra-high voltage systems. The thicker ceramic substrate also provides greater heat capacity and heat dissipation capability, balancing local heat distribution, suppressing temperature rise and resistance drift caused by transient pulses or overloads, and improving operational stability.

[0037] A lead wire 1 is inserted into the circular lead wire through hole 7. The front end of the lead wire 1 is provided with a nail head 11, which forms a mechanical limiting fit with the ceramic substrate 2. The nail head 11 has a T-shaped or disc-shaped structure.

[0038] The nail head 11 passes through the circular lead hole 7 on the ceramic substrate 2 and is welded to the silver electrode layer 6, forming a dual fixing structure of mechanical limiting and welding between the nail head 11 and the ceramic substrate 2. When the product encounters extreme working environments such as oil immersion, the entire UHV resistor is exposed to the air due to seepage and loss. At this time, the solder part on the electrode surface of the working UHV resistor will melt or even disappear due to the heat generated by the UHV. Under this structure, the lead 1 can still be connected to the silver electrode layer 6 normally, which extends the service life of the UHV resistor to a certain extent, and at the same time saves time for subsequent maintenance, reducing the potential danger and maintenance cost to the UHV circuit.

[0039] The circular lead-through hole 7 structure allows the nail-head lead 1 to pass through and be fixed at both ends, forming an integrated design of mechanical locking and electrical connection, effectively preventing the solder joint from falling off under oil immersion vibration and thermal expansion and contraction. At the same time, the lead 1 increases the conductive contact area at the end, making the current distribution more uniform, reducing the electric field concentration effect at the end, and minimizing the risk of localized electrical breakdown. Compared with the traditional "end-face electrode + flat lead" design, this structure has higher tensile strength and more stable oil immersion sealing.

[0040] Silver electrode layers 6 are printed on both ends of the ceramic substrate 2. The silver electrode layers 6 extend to the periphery of the circular lead through-hole 7. The lead 1 is welded and fixed to the silver electrode layers 6. The silver electrode layers 6 are formed by high-temperature sintering of silver-palladium alloy conductive paste. The edges are designed with rounded corners. The shape of the silver electrode layers 6 is trapezoidal, rectangular, arc-shaped, sawtooth-shaped, or a combination of trapezoidal and arc-shaped.

[0041] The silver electrode layer 6 is constructed using a silver-palladium alloy conductive paste, which is sintered at high temperature to form a dense conductive layer. This electrode offers the following advantages in ultra-high voltage resistors: High conductivity and low contact resistance: The silver electrode layer 6 ensures stable low-ohmic contact even under high voltage and high current density, reducing heat dissipation. Strong oil corrosion resistance: The surface of the silver electrode layer 6 and the encapsulation layer together form a dense interface, preventing the penetration of active components (such as aromatic free radicals) from benzyl toluene oil, thus avoiding metal migration and electrochemical corrosion. Optimized edge shape: The electrode edges feature a rounded transition design, reducing the risk of tip discharge under high voltage and ensuring the continuity and uniformity of the electric field distribution. High adhesion structure: When welding nail-head leads, the electrode thickness and formulation can withstand thermal shock of ≥250℃ without delamination, ensuring structural stability in long-term oil immersion environments.

[0042] A serpentine resistor strip 5 is printed on the surface of the ceramic substrate 2, and the two ends of the serpentine resistor strip 5 are electrically connected to the silver electrode layer 6.

[0043] The surfaces of the serpentine resistor strip 5 and the silver electrode layer 6 are covered with an encapsulation film 3, which is an organic material dielectric film coating resistant to benzyltoluene; the encapsulation film 3 is in the state of glass glaze and its thickness is 0.3mm to 0.8mm.

[0044] In this application, the width of the serpentine resistor strip 5 is 0.5mm to 2mm, the spacing between adjacent rails is 1.5mm to 2.5mm, and the height of the rail is 16mm to 18mm.

[0045] In this application, the surface of the ceramic substrate 2 is also provided with a resistance value mark 4, and the resistance value mark 4 and the encapsulation film 3 are respectively located on different surfaces of the ceramic substrate 2 or the encapsulation film 3 covers the outside of the resistance value mark 4.

[0046] In this application, when the silver electrode layer 6 is trapezoidal, its bottom edge faces the interior of the ceramic substrate 2, and its top edge is close to the circular lead hole 7.

[0047] The application of trapezoidal electrodes in ultra-high voltage (UHV) plate glass enamel resistors offers the following significant advantages: More uniform electric field distribution and suppression of end discharge: Traditional rectangular or right-angled electrodes easily form electric field concentration areas at their edges, especially in UHV operation or oil-immersed environments, easily inducing local surface discharge. Trapezoidal electrodes have smaller edge angles, resulting in a smoother transition of electric field lines at the electrode ends, reducing electric field spikes and significantly improving the local electric field uniformity and end insulation withstand voltage performance of the resistor. Enhanced adhesion and thermal stress release in the soldering area: The trapezoidal electrode is wider on the outer side and narrower on the inner side, allowing the lead solder joints to be distributed over a larger area, resulting in a more thorough bonding between the solder and the electrode. This structure can disperse mechanical and thermal stresses under thermal cycling or vibration conditions, reducing solder fatigue cracks and improving the mechanical stability and conductivity reliability of the lead connections. This is particularly important for UHV systems that are exposed to benzyl toluene oil for extended periods and experience significant temperature variations. Improved corrosion resistance of electrodes in oil immersion environments: The gradient structure of the trapezoidal electrode facilitates complete coverage of the encapsulation film 3 at the electrode edge, forming a natural transition interface and avoiding abrupt changes in the thickness of the encapsulation layer at the electrode edge. This effectively prevents benzyltoluene molecules from penetrating into the resistive film layer from the electrode edge, thereby improving resistance to oil chemical corrosion and oxidation, and extending the service life of the device in oil immersion. More reasonable potential matching between the silver electrode layer 6 and the serpentine resistance band 5: The serpentine resistance band 5 has a multi-peak, multi-valley serpentine structure, allowing the trapezoidal electrode to form a smooth transition at its starting and ending points, reducing localized high current density caused by "sharp access," improving the potential balance and current distribution uniformity of the entire resistive conduction path, and further enhancing the overall power carrying capacity and pulse resistance performance.

[0048] It should be noted that although the silver electrode layer 6 in this embodiment adopts a trapezoidal structure, the electrode shape is not limited to this. In different application scenarios, the structure can be adjusted according to the voltage level, power density, package size, and oil immersion dielectric characteristics. For example: rectangular electrodes: suitable for low- and medium-voltage devices, easy to manufacture, and suitable for mass production; arc electrodes: can further reduce the electric field concentration effect in ultra-high voltage applications; sawtooth or composite transition electrodes: can achieve a uniform distribution of the potential gradient within a limited space; trapezoidal and arc composite electrodes: combine mechanical stability and electrical uniformity, suitable for high-temperature oil-immersed long-life products.

[0049] Therefore, the electrode shape described in this utility model can be optimized according to actual needs. Its core technical point is to achieve long-term stability and high insulation performance of ultra-high voltage resistors in oil immersion environment by controlling the electric field of electrode geometry and packaging.

[0050] After the resistor strip and electrode layer are sintered at high temperature, an encapsulation film 3 is printed on the surface. This film is a benzyltoluene-resistant organic dielectric film coating. This coating is sintered at 500-600℃ to a glassy glaze state, forming a dense insulating protective layer with excellent heat resistance and impermeability. In a benzyltoluene-immersed environment, the encapsulation layer effectively prevents oil molecules from penetrating, preventing oxidation or swelling of the glass glaze film, thereby significantly improving the stability and lifespan of the resistor.

[0051] The substrate surface is printed with a resistor strip 5, which is a serpentine resistor circuit with seven peaks at the top and six troughs at the bottom. By extending the conductive path and increasing the creepage distance along the surface, the high voltage resistance and the uniformity of the electric field distribution are improved. The two ends of the resistor strip 5 are connected to silver electrodes 6, which are used to solder to the lead wire 1 for conduction.

[0052] The resistor strip 5 is formed on the surface of the ceramic substrate 2 using a thick-film printing process, and its shape is an asymmetrical serpentine structure with "six peaks on top and seven troughs on the bottom". Compared with the traditional equidistant serpentine pattern, this layout has the following advantages: it increases the conductive path length by about 5-15%, improving the withstand voltage; it disperses the local electric field concentration and improves the potential gradient distribution; it increases the creepage distance and reduces the probability of surface flashover; and it reduces parasitic inductance and capacitance effects through the reverse adjacent branch layout.

[0053] Furthermore, resistor strip 5 is printed on the surface of ceramic substrate 2 in the form of a serpentine conductive pattern, with a basic structure of "seven peaks on top and six troughs on the bottom". In actual production, the number of peaks and troughs can be adjusted according to the target resistance value, power density, and withstand voltage level, such as variant forms like "six peaks on top and seven on the bottom" or "eight peaks on top and nine on the bottom".

[0054] More specifically, the width and spacing of the conductive rails are set as follows: the width of the resistor rails ranges from 0.5mm to 2mm, the spacing between adjacent rails ranges from 1.5mm to 2.5mm, and the height of the rails ranges from 16mm to 18mm. A smaller linewidth can increase the resistance density, while a larger spacing can increase the creepage path and reduce the electric field coupling between adjacent rails.

[0055] Furthermore, in this embodiment, the guide rail width of resistor strip 5 is 1.3mm, the guide rail height is 18mm, and the spacing between adjacent guide rails is 1.7mm. These parameters are within the optimal range for the aforementioned guide rail width and spacing. In the actual research and development and production of this ultra-high voltage resistor, we conducted tests and verifications within this optimal range. The relevant test and verification data are presented below:

[0056] 1. With the height and spacing of the resistor rails remaining constant, the relevant performance of ultra-high voltage resistors with different rail widths was tested. Specifically, the following parameters were measured: (Surface withstand voltage: in benzyltoluene oil, 25 ℃, AC voltage increase, 1 kV / s increments, recording the maximum steady-state voltage without flashover / breakdown (unit: kV); Temperature rise: under rated power load, after the oil temperature reaches a steady state of 150 ℃, the temperature rise of the resistor body relative to the oil temperature was measured (°C); Resistance drift: after aging in benzyltoluene at 150 ℃ for 1000 h, ΔR / R (%) was measured; Failure rate: in each group of 10 samples, flashover or ΔR / R > ±2% during the withstand voltage / aging test was considered a failure, and the number of failed samples was recorded). The experimental data are shown in Table 1 below.

[0057] Table 1. Experimental data on the relevant performance of ultra-high voltage resistors with different guide rail widths.

[0058]

[0059] In the chip-type glass-glazed ultra-high voltage resistor of this invention, the width of the conductive rails is a crucial geometric parameter determining the conductor cross-sectional area, current density distribution, and local thermal field distribution. To investigate the impact of the conductive rail width on device performance, multiple sets of samples were prepared by varying only the conductive rail width while keeping other structural parameters such as the spacing between adjacent rails, peak height, and number of peaks and troughs constant. These samples underwent surface withstand voltage tests, rated power temperature rise tests, and 1000-hour aging tests in a benzyltoluene oil immersion environment. The test results show that the conductive rail width has a significant effect on the resistor's withstand voltage capability, temperature rise level, and long-term resistance stability.

[0060] When the guide rail width is too small (e.g., less than 0.5 mm), the effective cross-sectional area of ​​the conductive rail is insufficient. Under rated power and pulsed operating conditions, the current density per unit cross-section increases significantly, leading to a sharp rise in local ohmic heat on the conductive rail and the formation of hot spots. At the same time, the excessively narrow line width places high demands on the dimensional control of the thick film printing and sintering processes, easily resulting in process defects such as burrs on the line edges, broken lines, incomplete sintering, and uneven printing. These defects are prone to evolving into electric field concentration points and stress concentration areas under high electric field and high temperature oil immersion conditions, promoting the initiation of local microcracks or degradation of the resistive film, thus exhibiting higher temperature rise, greater resistance drift, and a certain proportion of failed samples.

[0061] When the guide rail width is controlled within the range of 0.5–2.0 mm, a better match is achieved between the conductive cross-sectional area and the current magnitude. On the one hand, this provides sufficient current carrying capacity, significantly reduces the current density per unit cross-section, alleviates localized heating, and ensures that the overall temperature rise of the resistor band remains at a low and uniform level. On the other hand, within this width range, the conductive rail lines are stably formed, the printing and sintering processes are easy to control, the conductive film has good continuity and smooth edges, and the internal stress distribution of the resistive film is relatively uniform, making it less likely to form localized stress concentration points. Therefore, within this width range, the resistor exhibits a high surface withstand voltage level, a low temperature rise, and a small resistance drift under ultra-high voltage oil immersion conditions. Long-term aging tests have confirmed that the failure rate of the samples is significantly reduced, and even failures may not occur.

[0062] When the width of the guide rail continues to increase (e.g., greater than 2.0 mm), although the conductor cross-sectional area further increases, under the constraint of the given ceramic substrate size, the number of bends and the unfolding density of the serpentine guide rail are forced to decrease. This shortens the equivalent conductive path length and the creepage distance along the surface, and the overall voltage gradient is concentrated on fewer path segments, resulting in a more concentrated electric field distribution and a decrease in the surface withstand voltage. At the same time, an excessively large guide rail width can also cause the potential difference in some areas to transition within a short distance, creating new electric field concentration areas at the interface between the resistive film and the ceramic substrate and at the edge of the guide rail. This, combined with the thermal stress and interface stress caused by the high-temperature oil immersion environment, makes it easier to induce local insulation degradation and resistive film aging, manifested as a decrease in withstand voltage, an increase in temperature rise, and an exacerbation of resistance drift, with a significant increase in sample failure rate.

[0063] In summary, based on the experimental results of samples with different conductive rail widths and the above-mentioned physical mechanism analysis, it can be determined that when the conductive rail width is preferably set in the range of 0.5mm to 2mm, a reasonable balance can be achieved between the conductive cross-sectional area, current density, electric field distribution, and thermal field distribution. This allows the ultra-high voltage resistor of this invention to have high surface withstand voltage, low temperature rise, and good long-term resistance stability under benzyltoluene oil immersion conditions.

[0064] 2. With the width and spacing of the resistor rails remaining constant, the relevant performance of ultra-high voltage resistors with different rail heights was tested. Specifically, this included: surface withstand voltage (kV): AC boost test in benzyltoluene oil immersion environment; temperature rise (°C): measured after steady-state operation in oil at 150°C with the same load power; resistance drift ΔR / R (%) over 1000 hours; failure rate (number of failed components out of 10). The experimental data are shown in Table 2 below.

[0065] Table 2. Experimental data on the relevant performance of ultra-high voltage resistors with different guide rail heights.

[0066]

[0067] In this invention, the resistor strip adopts a serpentine structure with seven peaks at the top and six troughs at the bottom. The guide rail height is a crucial geometric parameter determining the extent of the conductive rail spread and the voltage gradient distribution. Under the condition of changing only the guide rail height while keeping the conductive rail width, guide rail spacing, and the number of peaks and troughs constant, oil immersion withstand voltage, rated power temperature rise, and 1000-hour aging tests were conducted on samples with different guide rail height values. The results show that the guide rail height has a significant impact on the electric field distribution, thermal distribution, and long-term stability of the resistor.

[0068] When the guide rail height is less than 16mm, the rotation amplitude of the serpentine conductive rail is small, the equivalent conductive path length is insufficient, and the voltage drop is concentrated in a limited number of transition intervals, making the local electric field at the transition points significantly higher than other areas. Under high-voltage conditions of benzyltoluene oil immersion, these local high-field regions are prone to forming surface micro-discharge or flashover channels, causing degradation of the resistive film material and migration of the interface electrode, resulting in lower surface withstand voltage and increased resistance drift, thus increasing the probability of failure.

[0069] When the guide rail height is controlled within the range of 16–18 mm, the extent of the serpentine conductive rail's expansion matches the effective area of ​​the ceramic substrate, resulting in a more balanced potential difference distribution between adjacent conductive branches, a smooth electric field transition at transition points, and optimal overall electric field uniformity. Simultaneously, a moderately increased path length helps disperse the voltage gradient per unit length, reducing the peak electric field at single points; the current distribution on the serpentine guide rail is more uniform, avoiding the formation of localized overheating areas and maintaining a low temperature rise at rated power. Therefore, within this height range, the resistor exhibits a high withstand voltage rating, minimal resistance drift, and no sample failure during long-term oil-immersion high-temperature operation, indicating that the guide rail height value within this range achieves a good balance between electric and thermal field distribution.

[0070] When the guide rail height exceeds 18mm, the number of bends and the bending amplitude of the serpentine guide rail increase significantly. The conductive film is prone to uneven sintering thickness and residual stress concentration at the turning points and edges. On the one hand, these stress concentration points become crack initiation sources in the high-temperature oil immersion environment; on the other hand, they can evolve into new local high-field regions under the influence of an electric field, inducing micro-discharge and insulation degradation. Simultaneously, the excessively extended serpentine path leads to excessively long and densely packed current paths in some conductive branches, resulting in increased local current density and temperature rise. After long-term aging, resistance drift and failure rate increase significantly.

[0071] In summary, based on the experimental results of samples with different guide rail heights and the above physical mechanism analysis, it can be seen that when the guide rail height is preferably 16-18mm, the serpentine resistor strip is in a better state in terms of conductive path length, voltage gradient distribution, stress distribution and heat dissipation capacity, thus enabling the resistor to obtain higher surface withstand voltage and better long-term stability under ultra-high voltage benzyl toluene oil immersion conditions.

[0072] 3. With the width and height of the resistor rails remaining constant, test the relevant performance of the UHV resistors with adjacent rail spacing. Specifically, this includes: (surface withstand voltage (kV): in benzyltoluene oil, 25℃, AC voltage boost until flashover / breakdown; temperature rise ΔT (℃): the resistor body temperature rise after steady-state at 150℃ oil temperature under the same load power; resistance drift ΔR / R (%) after 1000 hours: after aging in benzyltoluene at 150℃ for 1000 hours; failure rate: in each group of 10 resistors, flashover, breakdown, or ΔR / R > ±2% is considered failure). The experimental data are shown in Table 3 below.

[0073] Table 3. Experimental data on the relevant performance of ultra-high voltage resistors with adjacent guide rail spacing.

[0074]

[0075] In the chip glass glaze ultra-high voltage resistor of this invention, the spacing between adjacent conductive rails is a crucial geometric parameter determining the electric field distribution and surface insulation performance. Under the condition of varying only the rail spacing while keeping the resistance band width, peak height, and number of peaks and troughs constant, samples with different rail spacing values ​​were subjected to benzyltoluene oil immersion withstand voltage tests, rated power temperature rise tests, and 1000-hour aging tests. The test results show that S has a significant impact on the resistor's electric field coupling degree, leakage characteristics, and long-term resistance stability.

[0076] When the spacing between adjacent conductive rails is too small (e.g., less than 1.5 mm), the electric field lines between them are highly concentrated in the narrow gap, increasing the degree of electric field coupling and significantly raising the local electric field strength. In ultra-high voltage oil-immersion environments, this high-field-strength, narrow-gap region easily forms surface micro-discharge channels, causing localized degradation of the insulating dielectric and resistive film surface, manifested as lower surface withstand voltage and increased leakage current. Furthermore, excessively close proximity enhances thermal coupling between the conductive rails, leading to increased local temperature rise and accelerating the aging process of the resistive film material, resulting in increased resistance drift and higher failure rate.

[0077] When the spacing between adjacent conductive rails is controlled within the range of 1.5mm to 2.5mm, the electric field lines between adjacent conductive branches are relatively uniformly distributed, and the potential gradient exhibits a smooth transition along the surface direction. This eliminates the problem of electric field concentration under narrow gap conditions and avoids the sudden potential change caused by excessive spacing. At this point, the surface withstand voltage reaches a high value, and the leakage current is at a low level. Simultaneously, a moderate thermal coupling relationship is maintained between each conductive rail, resulting in a low and uniform temperature rise of the resistive film under load conditions. This is beneficial for suppressing the thermal aging of the resistive film material and electrode interface, reducing long-term resistance drift and device failure rate.

[0078] When the spacing between adjacent conductive rails continues to increase (e.g., greater than 2.5 mm), the number of bends and the effective length of the serpentine conductive rails decrease to fit the given ceramic substrate size, shortening the surface creepage path and reducing the overall withstand voltage. Simultaneously, the "blank areas" between the conductive rails increase, leading to discontinuous potential distribution in some areas, and localized electric field concentration reappears near the edges and turning points. Furthermore, the thermal coupling between the conductive rails weakens, and the current density carried by some conductive paths relatively increases, easily forming localized high-temperature zones, increasing temperature rise and accelerating resistance drift.

[0079] Therefore, based on the above test results and physical mechanism analysis, it can be determined that when the spacing between adjacent conductive rails is preferably set within the range of 1.5mm to 2.5mm, a better balance can be achieved between electric field distribution, surface creepage distance, and heat distribution. This allows the ultra-high voltage resistor of this invention to have high surface withstand voltage, low leakage current, and good long-term resistance stability under benzyltoluene oil immersion conditions.

[0080] Through the above univariate experiments and physical mechanism analysis of the guide rail width, guide rail height, and adjacent guide rail spacing, it can be seen that this utility model does not simply adopt a serpentine pattern, but optimizes the resistor strip pattern within a defined range of geometric parameters. Preferably, when the guide rail width is 0.5mm to 2mm, the adjacent guide rail spacing is 1.5mm to 2.5mm, the guide rail height is 16mm to 18mm, and a serpentine structure with seven peaks and six troughs is used, the resistor strip achieves optimal matching in terms of conductive cross-sectional area, current density, electric field distribution, path length, and heat distribution. This enables the resistor to achieve high surface withstand voltage, low temperature rise, and excellent long-term resistance stability under benzyltoluene oil immersion ultra-high voltage conditions.

[0081] Working principle and effects: When the resistor is connected to a high-voltage circuit, the voltage is distributed and conducted along the serpentine resistance band, and the current is led out through the pin-head leads at both ends. The thick substrate structure provides sufficient dielectric thickness to prevent through-through and breakdown; the serpentine rail structure extends the resistance path and disperses the electric field; the pin-head lead structure achieves both mechanical and electrical fixation; the encapsulation film forms an oil-isolated protective layer to avoid chemical corrosion. This combined structure effectively improves the resistor's withstand voltage rating, thermal shock resistance, and long-term stability in ultra-high voltage oil-immersion environments.

[0082] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A high voltage resistor with a lead structure having a hole, which is suitable for oil-immersed operation, characterized in that, The ceramic substrate (2) is provided with circular lead through holes (7) at both ends symmetrically; A lead wire (1) is arranged in the circular lead through hole (7), and the front end of the lead wire (1) is provided with a nail head (11) which is in mechanical limiting cooperation with the ceramic substrate (2); The both end surfaces of the ceramic substrate (2) are printed with silver electrode layers (6) which extend to the periphery of the circular lead through hole (7), and the lead wire (1) is welded and fixed with the silver electrode layer (6); The surface of the ceramic substrate (2) is printed with a serpentine resistance band (5) which is electrically connected with the silver electrode layer (6) at both ends; The surface of the serpentine resistance band (5) and the silver electrode layer (6) is covered with an encapsulation film (3) which is a benzyltoluene-resistant organic material medium film coating.

2. The high voltage resistor with a lead structure having a hole according to claim 1, which is suitable for oil-immersed working conditions, characterized in that: The thickness of the ceramic substrate (2) is 2mm, and the ceramic substrate (2) is an alumina ceramic substrate which has a dielectric strength of 10-12kV / mm in an oil immersion environment.

3. The high voltage resistor with a lead structure having a hole according to claim 1, which is suitable for oil-immersed working conditions, characterized in that: The shape of the nail head (11) is T-shaped or disc-shaped structure.

4. The high voltage resistor with a lead structure having a hole according to claim 1, which is suitable for oil-immersed working conditions, characterized in that: The silver electrode layer (6) is formed by high-temperature sintering of silver-palladium alloy conductive paste, and the edge thereof is designed with a round corner transition, and the shape of the silver electrode layer (6) is trapezoidal, rectangular, circular arc, sawtooth or a composite shape of trapezoidal and circular arc.

5. The high voltage resistor with a lead structure having a hole according to claim 4, which is suitable for oil-immersed working conditions, characterized in that: When the silver electrode layer (6) is trapezoidal, the bottom edge faces the inside of the ceramic substrate (2), and the top edge is close to the circular lead through hole (7).

6. The high voltage resistor with a lead-through structure for oil-immersed service according to claim 1, characterized in that: The guide rail width of the serpentine resistance band (5) is 0.5mm-2mm, the adjacent guide rail spacing is 1.5mm-2.5mm, and the guide rail height is 16mm-18mm.

7. The high voltage resistor with a lead-through structure for oil-immersed service according to claim 1, characterized in that: The encapsulation film (3) is in a glass glaze state, and the thickness thereof is 0.3mm-0.8mm.

8. The high voltage resistor with a lead-through structure for oil-immersed service according to claim 1, characterized in that: The ceramic substrate (2) is further provided with a resistance value mark (4), and the resistance value mark (4) and the encapsulation film (3) are located on different surfaces of the ceramic substrate (2) respectively or the encapsulation film (3) covers the outside of the resistance value mark (4).

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