An adjustable capacitance water-cooled laminated busbar for LLC resonant inverter

Abstract

This application provides an adjustable capacitance value water-cooled laminated busbar for LLC resonant inverters, relating to the field of induction heating power supplies. The busbar includes a laminated busbar, water-cooling pipes, resonant capacitors, insulating pads, copper nuts, and insulating nuts. Multiple resonant capacitors are spaced apart on one side of the laminated busbar, each containing multiple terminals. These terminals are embedded in pre-fabricated through-holes in the laminated busbar, with gaps between the terminals and the inner walls of the through-holes. Copper nuts or insulating nuts are selectively fitted into the gaps between the terminals and the through-holes. Terminals fitted with copper nuts are conductive to the laminated busbar, while terminals fitted with insulating nuts are insulated from the laminated busbar. Water cooling is coiled around the surface of the laminated busbar surrounding the resonant capacitors. Through structural optimization and adjustable capacitance design, the device's adaptability is improved, its operating frequency is stabilized, and its service life is extended. It also provides efficient heat dissipation and allows for rapid and precise on-site capacitance adjustment.

Description

Technical Field

[0001] This application belongs to the field of induction heating power supply technology, specifically relating to an adjustable capacity water-cooled laminated busbar for LLC resonant inverters. Background Technology

[0002] Currently, my country's traditional smelting processes are nearing saturation. Coupled with the demand for smelting higher-strength and more diverse alloys, the heating power and frequency of induction heating power supplies have significantly increased compared to the past. High-power induction heating power supplies generally employ resonant capacitor banks with fixed capacitance values. The LLC resonant frequency is extremely sensitive to changes in load inductance. In actual production, changing different workpieces or crucibles will cause changes in load inductance, causing the system to deviate from the optimal resonant point. This not only reduces heating efficiency and quality but may also threaten device safety due to increased capacitor voltage. Currently, the existing solution for adjusting the capacitor is to replace the entire capacitor bank, but this process is cumbersome, time-consuming, and costly.

[0003] Furthermore, under mid-frequency currents reaching thousands of amperes, the stacked busbars generate significant heat due to the skin effect and proximity effect. In traditional uniformly distributed water-cooling designs, an excessively high stacking ratio between the L and N busbars poses a risk of localized overheating. However, insufficient stacking ratio between the L and N busbars generates a strong leakage magnetic field, heating the surrounding metal structure. Currently, in water-cooling applications, to balance heat dissipation and low inductance, the stacking ratio between busbars is typically controlled between 70% and 80%. Summary of the Invention

[0004] Based on the shortcomings of existing technologies, this application provides a method for calculating resonant capacitance, designing water-cooled layer stacking, and using the technology in induction heating power supply systems. Through structural optimization and adjustable capacitance design, it improves equipment adaptability, stabilizes operating frequency, and extends service life. It also provides efficient heat dissipation and allows for rapid and precise on-site capacitance adjustment.

[0005] The following technical solution is adopted: An adjustable capacitance water-cooled laminated busbar for an LLC resonant inverter includes a laminated busbar, water-cooling pipes, resonant capacitors, insulating pads, copper nuts, and insulating nuts. Multiple resonant capacitors are spaced apart on one side of the laminated busbar. Each resonant capacitor contains multiple terminals, which are embedded in pre-made through-holes in the laminated busbar, with gaps between the terminals and the inner walls of the through-holes. A copper nut or an insulating nut is selectively fitted into the gap between the terminals and the through-holes. The terminal with the copper nut is conductive to the laminated busbar, while the terminal with the insulating nut is insulated from the laminated busbar. Water cooling is coiled around the surface of the laminated busbar surrounding the resonant capacitors.

[0006] Furthermore, the terminal has a cylindrical structure, with an annular insulating attachment fixed to the outer periphery of the root of the terminal, and the head of the terminal extends beyond the insulating attachment; multiple array-arranged through holes are evenly spaced on the stacked busbar, the positions of the through holes correspond one-to-one with the positions of the terminals, and the inner diameter of the through holes is tightly fitted with the outer diameter of the insulating attachment.

[0007] Furthermore, the stacked busbar includes an L-pole busbar and an N-pole busbar, which are attached together to form a stacked busbar, with a stacking ratio of 90%. Furthermore, each of the resonant capacitors is provided with a support plate at its lower end, and both ends of the support plate are fixedly connected to the supporting sheet metal of the frame.

[0008] Furthermore, it is applied to a voltage-source series-parallel LLC resonant inverter. The topology is a phase-shifted full-bridge followed by an LLC resonant tank circuit. It mainly consists of four parts: DC input, IGBT inverter circuit, resonant tank circuit, and load. Among them, the resonant tank circuit is a series resonant inductor. Parallel resonant inductor resonant capacitor composition.

[0009] Furthermore, the design methodology includes the following steps: ① Capacitor Design During the capacitor design phase, the angular frequency is calculated based on the system resonant frequency. and series resonant inductor Parallel resonant inductor The desired ideal resonant capacitance value can be obtained. Cr， Based on system voltage, current and other parameters, the resonant capacitor is selected, including the equivalent inductance value. By series resonant inductor Parallel resonant inductor Decide: ② Water-cooled layer stacking design During the design phase of the stacked busbar, electromagnetic-thermal coupling simulation is used to simulate the current path and heat distribution of the busbar under rated operating current and specific frequency. Based on the simulation results, the routing of the water-cooling pipes on the copper busbar is arranged reasonably. ③ Based on the design results of the first two steps, assemble the resonant capacitor, water-cooled layer stack, copper nut, insulating nut, and insulating accessories. Install the copper nut or insulating nut through the terminals of the resonant capacitor to control the total capacitance of the resonant capacitor. ④ Respond to changes in on-site working conditions; When the on-site operating conditions change, the parallel resonant inductor Changes occur, causing the system inductance value to change. L d Changes occur, causing the resonant frequency to change. f r An offset has occurred; The resonant capacitance can be quickly changed by adding or removing copper nuts to adjust the total capacitance. Cr The capacitance value makes the resonant frequency... f r Return to the rated value to stabilize the system's operating state and prevent a decrease in heating effect and system efficiency.

[0010] Moreover, the resonant frequency f r From the equivalent inductance value 、 Resonant capacitor Cr Decide ， The equivalent inductance value By series resonant inductor Parallel resonant inductor Decide: .

[0011] Furthermore, in an LLC resonant inverter, the capacitor voltage... With resonant current Resonant frequency f r Resonant capacitor Cr Related: .

[0012] In summary, the technical solutions provided in the embodiments of this application have the following technical effects or advantages: 1. This invention solves the problem of uneven heating of high-current busbars by using a thermal simulation-guided stacked drainage cold pipe design, thereby improving power density and system reliability.

[0013] 2. This invention effectively suppresses magnetic leakage through a busbar structure with a high stacking ratio, reduces induction heating interference to surrounding structures, and improves overall efficiency.

[0014] 3. This invention achieves rapid adjustment of the resonant capacitor by combining machined insulating accessories, copper nuts, and the water-cooling layer stacked in this solution. This allows the equipment to flexibly adapt to varying field loads without replacing the entire capacitor bank, improving the equipment's adaptability to operating conditions and saving time and costs.

[0015] 4. When the load inductance changes, the present invention can quickly adjust the capacitance value by adjusting the structure, so that the resonant frequency returns to the rated value, stabilize the system working state, and is especially effective in working conditions that are sensitive to heating frequency, thereby improving heating efficiency and quickly matching new production needs.

[0016] 5. When the capacitor voltage in the main circuit becomes abnormal due to load changes, the present invention can quickly adjust the structure to respond and stabilize the resonant frequency at the rated value, thereby avoiding voltage abnormalities and protecting the equipment. Attached Figure Description

[0017] Figure 1 This is a diagram showing the overall structure of the capacitor and its stacked array.

[0018] Figure 2 This is a schematic diagram of a capacitor structure.

[0019] Figure 3 It is a layer stacking group structure.

[0020] Figure 4 It is a diagram showing the structure of rapid capacitance adjustment.

[0021] Figure 5 It shows the temperature distribution diagram and corresponding pipeline distribution diagram of the electromagnetic-thermal coupling simulation of the stacked array.

[0022] Figure 6 This is a circuit diagram of an LLC series-parallel resonant topology.

[0023] Reference numerals: 1. Water cooling pipe; 2. L-terminal busbar; 3. N-terminal busbar; 4. Resonant capacitor; 5. Support sheet metal; 6. Resonant inductor; 7. Insulating nut; 8. Copper nut; 9. Insulating pad; 10. Terminal; 11. Through hole. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0025] An adjustable capacitance water-cooled laminated busbar for LLC resonant inverters, see appendix. Figure 1 As shown, the specific structure includes L-terminal busbar 2, N-terminal busbar 3, water-cooling pipe 1, insulating pad 9, copper nut 8, insulating nut 7, resonant capacitor 4, and supporting sheet metal 5. Both L-bus 2 and N-bus 3 are flat plate structures that are attached to each other and stacked to form a stacked busbar. Water cooling pipes 1 are coiled around the outer surfaces of both L-bus 2 and N-bus 3. The water cooling pipes 1 are attached to the stacked busbar to facilitate heat conduction. The lower end of the stacked busbar is connected to a resonant inductor 6. In the stacked busbar, multiple resonant capacitors 4 are arranged at intervals on one side of the L-pole busbar. Each resonant capacitor 4 is provided with multiple terminals 10. A copper nut 8 or an insulating nut 7 is selected to be installed on the terminal 10. The terminal 10 with the copper nut 8 is connected to the stacked busbar, and the terminal 10 with the insulating nut 7 is insulated from the stacked busbar.

[0026] See appendix Figure 2 As shown, terminal 10 has a cylindrical structure, and an annular insulating attachment is fixed to the outer periphery of the root of terminal 10. The head of terminal 10 extends beyond the insulating attachment. See appendix Figure 3 The stacked busbar shown has multiple arrayed through holes evenly spaced, the positions of the through holes correspond one-to-one with the positions of the terminals 10, and the inner diameter of the through holes is closely matched with the outer diameter of the insulating accessories.

[0027] See appendix Figure 4 As shown, after the resonant capacitor 4 is assembled with the stacked busbar, the terminal 10 is inserted into the through hole. The insulating accessory is made of machined UPGM-203 material. By fixing the insulating accessory to the stacked busbar, it is attached to the resonant capacitor 4. Due to the physical isolation of the insulating accessory, the capacitor electrode is completely disconnected from the busbar, and the capacitor unit is not connected to the circuit.

[0028] After fixing the copper nut 8 to the laminated busbar, the electrode voltage of the resonant capacitor 4 is connected to the laminated busbar through the copper nut 8, thus enabling conduction. By changing the number of conducting terminals, the capacitance value can be quickly adjusted.

[0029] The total system capacitance can be increased or decreased by a multiple of the capacitance provided by each capacitor cell connected to each pin using the method described above. This avoids loose capacitor connections while achieving a reliable and rapid capacitance change process.

[0030] Each resonant capacitor 4 has a support plate at its lower end. Both ends of the support plate are fixedly connected to the support sheet metal 5 of the frame to maintain the stability of the installation structure of the resonant capacitor 4.

[0031] See appendix Figure 6 As shown, the above-mentioned stacked busbar is applied to a voltage-type series-parallel LLC resonant inverter. Its topology is a phase-shifted full bridge followed by an LLC resonant tank circuit. It mainly consists of four parts: DC input, IGBT inverter circuit, resonant tank circuit and load. The resonant tank circuit is composed of series resonant inductor Ls, parallel resonant inductor Lr (load / coil) and resonant capacitor Cr.

[0032] A design method for adjustable capacitance water-cooled laminated busbars for LLC resonant inverters, the specific implementation steps of which include: ① Calculation and selection of capacitor parameters During the capacitor design phase, the angular frequency is calculated based on the system resonant frequency. and series resonant inductor Parallel resonant inductor (Load / Coil) can be used to obtain the desired ideal resonant capacitance value. Cr， Based on system voltage, current and other parameters, the resonant capacitor is selected.

[0033] The equivalent inductance value By series resonant inductor Parallel resonant inductor Decide: The actual power of this embodiment is 500KW, and the heating frequency under operating conditions is... =6000 Hz Parallel resonant inductor (Load / Coil) = 1.8 μH, Series resonant inductor =8.4 μH, Load equivalent resistance =0.017Ω.

[0034] The capacitance value is calculated using the calculation method provided by this invention, and the current and voltage corresponding to the capacitor are selected according to the power and load.

[0035] Current on the resonant capacitor Select capacitor bank 520. μF, The capacitor bank has a total of 40 terminal connection points, each providing 13 μF The capacitance value.

[0036] ② Water-cooled layer stacking design In the design phase of the laminated busbar, this invention uses electromagnetic-thermal coupling simulation to simulate the current path and heat distribution of the busbar under rated operating current and specific frequency. Based on the simulation results, the routing of the water-cooling pipes on the laminated busbar is rationally arranged. Figure 5 As shown.

[0037] Based on the current on the resonant capacitor Heating frequency =6000 Hz, The selected capacitor bank structure and its shape were also considered, and a stacked structure was designed. Electromagnetic-thermal coupling simulation was used to model the current path and heat distribution of the busbar under rated operating current and specific frequency. (See attached image.) Figure 5 As shown.

[0038] Simultaneously, the stacking structure of the L-pole busbar and N-pole busbar is optimized. While ensuring insulation between busbars, the stacking ratio is increased to 90% or even higher. Terminal extension length is minimized as much as possible while ensuring electrical safety. The magnetic fields generated by reverse currents cancel each other out, reducing magnetic leakage and preventing abnormal heating of the cabinet and supporting sheet metal, thus reducing unnecessary losses and improving equipment efficiency.

[0039] The resonant frequency of this topology f r From the equivalent inductance value 、 Resonant capacitor Cr Decide 。 The equivalent inductance value By series resonant inductor Parallel resonant inductor Decide: ③ As required, assemble the resonant capacitor, water-cooling layer stack, copper nuts, insulating nuts, and insulating accessories. Based on the calculations in this embodiment, 37 copper nuts and 3 insulating nuts are installed before shipment to complete the overall assembly. See [link / reference]. Figure 1 As shown; Based on the capacitor's structural shape, a machined UPGM-203 insulating accessory is designed and fixed to the laminated busbar, attaching it to the resonant capacitor. Due to the physical isolation provided by the insulating accessory, the capacitor electrodes are completely disconnected from the busbar, and this capacitor unit is not connected to the circuit. After fixing the copper nut to the laminated busbar, the electrodes of the resonant capacitor are pressed against the laminated busbar to connect to the busbar. See [link to diagram]. Figure 3 As shown.

[0040] ④ Solutions for changes in on-site working conditions When on-site operating conditions change (such as changing workpieces, crucibles, etc.), the parallel resonant inductor Changes in the load / coil cause changes in the system inductance value. L d Changes occur, causing the resonant frequency to change. f r An offset occurs. Using the rapidly adjustable structure of this invention, the copper nut is added or removed to quickly change the resonant capacitance. Cr The capacitance value. To make the resonant frequency... f r Return to the rated value to stabilize the system's operating state and prevent a decrease in heating effect and system efficiency.

[0041] Meanwhile, in LLC resonance, the capacitor voltage With resonant current Resonant frequency f r Resonant capacitor Cr Related When the resonant frequency deviates, the capacitor voltage increases in an attempt to stabilize it, posing an insulation risk and potentially damaging the equipment. The rapidly adjustable structure of this invention allows for quick response, stabilizing the resonant frequency at its rated value while preventing voltage anomalies that could damage the equipment.

[0042] When the equipment is working on site, changes in on-site conditions (such as changing workpieces or crucibles) can cause the parallel resonant inductor to... (Load / Coil) from 1.8 μH Increased to 2.2 μH. This leads to the system inductance value L d Changes occur, causing the resonant frequency to change. f r Offset to This causes a shift in the resonant frequency, which significantly impacts processing conditions with high frequency requirements and reduces heating efficiency. Calculations indicate that the resonant capacitor value needs to be adjusted to 416. By using the stacked array design provided by this invention, and removing the five copper nuts from the existing stacked array, the resonant inductance value can be reduced from 480... It becomes 416 .

[0043] To bring the resonant frequency back to the rated value required for the processing conditions.

[0044] ⑤ At the same time, the voltage across the resonant capacitor will also change with the change of the load on site. Taking the current load change as an example, when the parallel resonant inductor (Load / Coil) from 1.8 μH Increased to 2.2 μH At that time, according to in For resonant current, The resonant capacitor voltage, frequency shift will cause changes in capacitive reactance, and thus... This causes fluctuations, increasing the voltage across the capacitor from 379V to 439V. This invention allows for adjustment of the capacitance value to stabilize the voltage. At the same time, it can also To keep the voltage within a safe range and avoid overvoltage risks, it is also necessary to avoid reducing the operating current while maintaining the frequency, which would reduce the overall power of the equipment and affect processing accuracy and technology.

[0045] Using the same method as ④, the capacitance value can be quickly adjusted by changing the number of copper nut blocks, so that the voltage on the resonant capacitor can be restored to the rated value, thereby improving the service life of the equipment.

[0046] The above-described embodiments of the present invention are mainly aimed at parallel resonant inductors. When the load / coil increases, the parallel resonant inductor... Even when the load / coil decreases, this method can still be used for adjustment and proper matching.

[0047] This invention solves the heat dissipation and interference problems through structural optimization, and solves the problem of fixed capacitance value through an original adjustable mechanism. The combination of the two improves the reliability, adaptability and service life of the equipment.

[0048] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of other embodiments of this disclosure upon considering the specification and the disclosure of practical truth. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described in this disclosure. The specification and embodiments are considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

Claims

1. An adjustable capacitance water-cooled laminated busbar for an LLC resonant inverter, characterized in that, The system includes a stacked busbar, water-cooling pipes, resonant capacitors, insulating pads, copper nuts, and insulating nuts. Multiple resonant capacitors are spaced apart on one side of the stacked busbar. Each resonant capacitor contains multiple terminals, which are embedded in pre-made through holes in the stacked busbar, with gaps between the terminals and the inner walls of the through holes. Copper nuts or insulating nuts are optionally installed in the gaps between the terminals and the through holes. Terminals with copper nuts are conductive to the stacked busbar, while terminals with insulating nuts are insulated from the stacked busbar. Water-cooling pipes are coiled around the surface of the stacked busbar surrounding the resonant capacitors.

2. The adjustable capacitance water-cooled laminated busbar for an LLC resonant inverter according to claim 1, characterized in that, The terminal has a cylindrical structure, with an annular insulating attachment fixed to the outer periphery of the root of the terminal, and the head of the terminal extends beyond the insulating attachment; multiple array-arranged through holes are evenly spaced on the stacked busbar, the positions of the through holes correspond one-to-one with the positions of the terminals, and the inner diameter of the through holes is tightly fitted with the outer diameter of the insulating attachment.

3. The adjustable capacitance water-cooled laminated busbar for an LLC resonant inverter according to claim 1, characterized in that, The stacked busbar includes an L-pole busbar and an N-pole busbar, which are attached together to form a stacked busbar, and the stacking ratio of the L-pole busbar and the N-pole busbar is 90%.

4. The adjustable capacitance water-cooled laminated busbar for an LLC resonant inverter according to claim 1, characterized in that, Each resonant capacitor has a support plate at its lower end, and both ends of the support plate are fixedly connected to the supporting sheet metal of the frame.

5. The adjustable capacitance water-cooled laminated busbar for an LLC resonant inverter according to claim 1, characterized in that, This is applied to a voltage-source series-parallel LLC resonant inverter. The topology is a phase-shifted full-bridge followed by an LLC resonant tank circuit. It mainly consists of four parts: DC input, IGBT inverter circuit, resonant tank circuit, and load. The resonant tank circuit is a series resonant inductor. Parallel resonant inductor resonant capacitor composition.

6. The adjustable capacitance water-cooled laminated busbar for an LLC resonant inverter according to claim 5, characterized in that, The design methodology includes the following steps: ① Capacitor Design During the capacitor design phase, the angular frequency is calculated based on the system resonant frequency. and series resonant inductor Parallel resonant inductor The desired ideal resonant capacitance value can be obtained. Cr， Based on system voltage, current and other parameters, the resonant capacitor is selected, including the equivalent inductance value. By series resonant inductor Parallel resonant inductor Decide: ② Water-cooled layer stacking design During the design phase of the stacked busbar, electromagnetic-thermal coupling simulation is used to simulate the current path and heat distribution of the busbar under rated operating current and specific frequency. Based on the simulation results, the routing of the water-cooling pipes on the copper busbar is arranged reasonably. ③ Based on the design results of the first two steps, assemble the resonant capacitor, water-cooled layer stack, copper nut, insulating nut, and insulating accessories. Install the copper nut or insulating nut through the terminals of the resonant capacitor to control the total capacitance of the resonant capacitor. ④ Respond to changes in on-site working conditions; When the on-site operating conditions change, the parallel resonant inductor Changes occur, causing the system inductance value to change. L d Changes occur, causing the resonant frequency to change. f r An offset has occurred; The resonant capacitance can be quickly changed by adding or removing copper nuts to adjust the total capacitance. Cr The capacitance value makes the resonant frequency... f r Return to the rated value to stabilize the system's operating state and prevent the heating effect from deteriorating and the system efficiency from decreasing.

7. The adjustable capacitance water-cooled laminated busbar for an LLC resonant inverter according to claim 6, characterized in that, The resonant frequency f r From the equivalent inductance value 、 Resonant capacitor Cr Decide ， The equivalent inductance value By series resonant inductor Parallel resonant inductor Decide: 。 8. The adjustable capacitance water-cooled laminated busbar for an LLC resonant inverter according to claim 7, characterized in that, In an LLC resonant inverter, the capacitor voltage With resonant current Resonant frequency f r Resonant capacitor Cr Related: 。

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