In the operation system of High-Voltage Power Supplies (HV Power supply), insulation performance is a core factor determining their safety, stability, and service life. Whether it is the high-voltage bus of a photovoltaic inverter or the internal control power supply of an EV charging station, if there is a flaw in the insulation system, it may cause equipment failure and shutdown at best, or lead to serious accidents such as electric leakage, arcing, and even breakdown at worst, resulting in significant economic losses and safety hazards. Vacuum impregnation technology, as a process solution that combines deep penetration and precise filling, is providing an efficient solution for the insulation upgrade of key components of HV power supplies with its unique mechanism. Especially when dealing with the insulation of micro gaps and complex structures, it demonstrates advantages that traditional processes cannot match.
1. Vacuum Impregnation: The Core Logic to Solve Insulation Pain Points of HV Power Supplies
The insulation challenge of HV power supplies essentially stems from the microstructural characteristics of their internal key components such as coils and bushings. Taking the stator winding of a generator as an example, the gaps formed by the winding of multi-layer wires and the micro-pores left when wrapping mica tapes, if not fully filled with insulating medium, can easily become "breakdown channels" under the action of high voltage. Traditional dipping processes rely on natural penetration under normal pressure, which not only makes it difficult to penetrate these micro gaps but also may form bubbles due to residual air, thereby reducing insulation performance.
The breakthrough of vacuum impregnation technology lies in completely changing the penetration path of the insulating medium through a two-step operation of "negative pressure environment - pressure filling". Firstly, the component to be processed is placed in a sealed dipping tank, and the vacuum is drawn to 0.01MPa with a pressure holding time of 20-30 minutes. This process can effectively extract the air and moisture inside the component, clearing obstacles for the penetration of insulating paint. Then, insulating paint (such as epoxy anhydride resin) is injected into the tank, and the pressure is increased to 0.3MPa. The pressure difference is used to push the insulating paint into every tiny pore and gap, forming a complete insulation layer without bubbles or gaps. The insulation resistance of components treated by this process can be increased to more than 100MΩ, far exceeding the performance index of traditional processes, perfectly meeting the strict requirements of HV power supplies for insulation strength.
2. Vacuum Impregnation Process Details Adapted to HV Power Supplies: Precise Control from Materials to Parameters
Not all vacuum impregnation solutions can meet the special needs of HV power supplies. Their process design must focus on the two cores of "high-voltage tolerance" and "environmental adaptability". In terms of material selection, the combination of low-resin mica tape and epoxy anhydride resin has become the mainstream. The low-resin mica tape has high mica content and excellent air permeability, is soft and easy to wind at room temperature, and can closely fit the surface of the wire to form a basic insulation layer. The epoxy anhydride resin has excellent electrical insulation, moisture resistance, and chemical resistance. After curing, it closely combines with the mica tape to form a composite structure with both strength and insulation performance.
The optimization of process parameters is also crucial. Taking the vacuum impregnation of HV power supply coils as an example, the pre-drying link needs to strictly control the temperature and time: if normal pressure pre-drying is adopted, the temperature should be set to (T±10)℃ according to the heat resistance grade of the insulating material; if pre-drying is carried out in a vacuum environment, the temperature is controlled at 80-110℃, and the heating process must be carried out slowly to avoid component deformation or incomplete moisture evaporation due to excessive temperature difference. In the impregnation stage, the viscosity of the insulating paint needs to be adjusted to 50-80mPa·s to ensure that it can penetrate quickly under pressure without waste due to excessive fluidity; the pressure holding time needs to be adjusted according to the thickness of the component, usually 30-60 minutes, to ensure that the insulating paint fully fills all gaps. The drying link is divided into two stages: solvent volatilization and paint base curing. In the first 2-3 hours, the temperature is controlled below the boiling point of the solvent (such as 80-100℃) to accelerate solvent volatilization and avoid surface crusting; in the subsequent 8-10 hours, the temperature is increased to 10K above the pre-drying temperature to fully cure the resin and form a stable insulation layer.
3. Practical Value of Vacuum Impregnation in HV Power Supply Scenarios: From Performance Improvement to Cost Optimization
In practical applications, the value of vacuum impregnation technology for HV power supplies is not only reflected in the improvement of insulation performance but also runs through the cost control and reliability guarantee of the entire equipment life cycle. Taking the high-voltage bus of a photovoltaic inverter as an example, the insulation components treated by vacuum impregnation can have their breakdown voltage increased by more than 30%, which can effectively resist the erosion of outdoor high-humidity and dusty environments, reduce the risk of insulation failure, reduce equipment failure rate by 20%-25%, and significantly reduce operation and maintenance costs and downtime losses.
In the high-voltage power supply module of EV charging stations, the advantages of vacuum impregnation are more prominent. The power supply of charging stations needs to withstand frequent high-load charging and discharging, and the insulation layer of internal coils is prone to aging and cracking due to temperature fluctuations and vibration. The coils treated by vacuum impregnation have a closer combination between the insulation layer and the wire, which can effectively buffer vibration and impact, and the thermal conductivity is increased by 15%-20%, which helps to reduce the operating temperature of the coil and extend the service life by 3-5 years. At the same time, the vacuum impregnation process can also shorten the dipping time - compared with the traditional process which takes several hours, vacuum impregnation can be completed in only 1-2 hours, and the utilization rate of insulating paint is increased to more than 90%, directly reducing material loss and production costs.
In addition, vacuum impregnation technology also provides possibilities for the miniaturization of HV power supplies. With the increasing requirements for integration of new energy equipment, the internal structure of HV power supplies is becoming more and more compact, and traditional insulation processes are difficult to handle complex micro-components. However, vacuum impregnation can accurately fill narrow gaps without additional increase in the thickness of insulating materials, reducing the volume of the power supply module by 10%-15% and adapting to the installation needs of more scenarios.
4. Future Trends: Collaborative Innovation between Vacuum Impregnation and HV Power Supply Technology
With the advancement of the dual-carbon policy and the continuous upgrading of HV power supply technology, vacuum impregnation technology is also developing in a more efficient and intelligent direction. On the one hand, the research and development of new insulating materials has injected new vitality into vacuum impregnation. For example, the application of nano-modified epoxy resin can reduce the dielectric loss factor of the insulation layer to below 0.001, further improving the operational stability of HV power supplies; on the other hand, the popularization of intelligent vacuum impregnation equipment, through the introduction of real-time monitoring systems for parameters such as temperature, pressure, and viscosity, realizes the automatic adjustment of the process and reduces human operation errors, ensuring the consistency of insulation performance of each batch of components.
In the context of HV power supplies developing towards higher voltage and higher power, vacuum impregnation technology will continue to play a key role. For example, in HV DC power supplies above 10kV, the combination of vacuum impregnation and Vacuum Pressure Impregnation (VPI) process can realize the multi-layer composite design of the insulation layer to meet the insulation needs in ultra-high voltage environments; in modular HV power supplies, the batch processing capacity of vacuum impregnation can adapt to large-scale production, providing process support for the industrial application of HV power supplies.
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