Analysis of the causes of Laminated Inverter Busbars failure: Multiple factors affecting equipment stability

In the inverter operating system, the Laminated Inverter Busbars serve as the core power transmission channel connecting critical components such as capacitors and IGBT modules. Their operational stability directly determines the inverter's performance and safety. It is understood that failure of the laminated bars can easily lead to serious faults in the inverter, such as overvoltage, overcurrent, or even direct short circuits, thereby affecting the normal operation of the entire power transmission system. Therefore, investigating the causes of failure and mitigating fault risks has become a key focus in the power electronics industry. The quality and design rationality of the laminated busbars are core factors affecting their service life.

Industry experts point out that the failure of inverter laminated busbars is not caused by a single factor. Among them, insulation aging and breakdown are the most important causes, which are mostly related to the long-term operating environment and manufacturing process. When inverters are in high-temperature conditions for a long time, the insulating materials such as PET, PEN, and PI inside the laminated bar will gradually become brittle and lose their insulating properties, eventually leading to interlayer short circuits. If the process control is not good during manufacturing, there will be gaps or bubbles in the insulation layer. Under the action of high-frequency and high-voltage bar voltage, partial discharge (PD) will occur, which will lead to insulation breakdown after long-term accumulation. In addition, improper treatment of the laminated edges and insufficient insulation distance (creep distance) can also easily cause interlayer edge flashover breakdown. This problem is particularly prominent in Laminated Busbars for High-Temperature Applications.

Manufacturing defects are also a significant cause of laminated busbar failure, directly affecting the structural stability and insulation performance of the bar. Uneven lamination or delamination is quite common. Due to insufficient bonding between the copper bar and the insulation layer, air accumulates at the delamination points, leading to partial discharge or electric field concentration, accelerating bar failure. If dirt, moisture, or metal shavings are present on the surface of the copper bar before lamination, it can cause local thinning of the insulation layer, even forming conductive channels and creating potential faults. At the same time, if burrs left over from the copper bar cutting process are not removed in time, they may puncture the insulation film, directly causing a short circuit. This places higher demands on the manufacturing precision of laminated copper bars.

Thermal expansion and mechanical stress damage further accelerate the failure rate of the laminated busbar. Frequent inverter start-up and shutdown lead to alternating high and low loads. Due to the different coefficients of thermal expansion of the copper bar and the insulation layer, repeated thermal expansion and contraction occur, generating peeling stress between the layers. This accelerates the separation of the insulation layer from the copper bar, resulting in thermal cycling fatigue damage. If the inverter is located in an environment with significant vibration, it will further exacerbate the fatigue fracture of the already fragile laminated material. This problem is particularly prominent in scenarios with significant vibration, such as automotive and wind power applications, posing a challenge to the stability of the Laminated Bus Bar for Windmill Inverter IGBT I/O.

Overvoltage and transient voltage surges can directly puncture the laminated busbar insulation, causing sudden failure. When the snubber circuit fails or is inadequately designed, the IGBT will generate extremely high voltage spikes on the bar during high-frequency switching. If these spikes exceed the insulation's tolerance limit, they will instantly puncture the insulation. In addition, DC input surges causing excessively high bar voltage can also directly damage the insulation, leading to bar failure. This places stringent requirements on the rationality of the laminated bar design.

Environmental chemical corrosion can also affect the service life of laminated busbars, indirectly causing failure. If the external environment is humid, or if corrosive gases seep into the inverter, the copper bars will oxidize and undergo electrochemical corrosion, which will then erode the laminated insulation layer, gradually reducing its insulation performance. Over time, this can lead to bar failure. This problem needs to be carefully prevented in outdoor photovoltaic and wind power scenarios, and it places higher demands on the protection design of Laminated Bars for Photovoltaic Inverters.

Industry experts summarize that the failure of Laminated Inverter Busbars is mostly the result of multiple factors such as thermal, electrical, and mechanical stress. Among these, the stability of the insulation system and the tightness of the manufacturing process are key to determining its service life. As inverters develop towards higher frequencies, higher voltages, and smaller sizes, the technical requirements for laminated bar power solutions will continue to increase. In the future, it will be necessary to further reduce the probability of laminated busbar failure by optimizing design, improving manufacturing precision, and strengthening protection measures, so as to provide solid support for the stable operation of inverters.

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