Technical article | Laminated copper busbar insulation materials - A brief discussion on flexible and rigid insulation and their parameters

The conductor insulation core of Laminated flexible busbar relies on flexible insulation materials, which are tightly bonded to the conductor through adhesive lamination process, forming a sealed protection at the edge of the conductor. Even under harsh atmospheric conditions, insulation failure can be avoided, and its flame retardancy can effectively reduce the flammability risk of busbar. The most widely used flexible insulation material currently is polyester (PET), which is available in transparent or white specifications and has become the preferred choice for most busbar applications due to its balanced performance.

PET material has a rated operating temperature of 105 ° C and can operate stably for a long time at this temperature; Its elongation rate exceeds 100%, and it is not easy to tear or thin in the production process of Laminated copper bars such as bending and conductor edge wrapping. It can also maintain the shape of the conductor even after exceeding the glass transition temperature; Provide various thicknesses such as 50 μ m, 125 μ m, 250 μ m, 350 μ m, etc., balancing economy and adaptability; At the same time, it has excellent relative leakage tracking index (CTI), which can shorten the creepage distance and meet the UL94-V0 flame retardant rating while achieving thinning.

Another type of high-performance flexible insulation material is polyimide (PI), which is brown or black in color and focuses on high temperature resistance. Its relative temperature index (RTI) exceeds 200 ° C, making it suitable for welding busbar components and avoiding insulation damage during heating. However, PI material has higher hardness, no mechanical stress relaxation points, poor surface quality, and is only suitable for applications below 600V. The standard thickness is only 25 μ m to 50 μ m, which is much more expensive than PET. Therefore, it is only used in specific high-temperature demand scenarios.

Flexible insulation and rigid insulation serve different functions in Laminated copper busbars, and their selection depends on the voltage level and insulation requirements of the application scenario. Flexible insulation is mainly used for insulation protection of conductor bodies and is the core component of the stacked busbar foundation. It can form optimal electrical seals at key positions such as conductor edges and vias, ensuring the insulation reliability of individual conductors.

Rigid insulation is used for the isolation between components of the finished Laminated bus bar for telecom, and its thickness is directly determined by the system operating voltage. The core goal is to optimize the critical electric field distribution and meet the requirements of partial discharge protection. The industry standard is to equip a rigid insulation with a thickness of 1mm per kilovolt voltage. The commonly used material is glass fiber reinforced polyester, with a thickness range of 1mm to 6mm. For example, a 3000V DC overhead line with a maximum operating voltage not exceeding 4800V requires the use of 5mm thick rigid insulation material. The higher the voltage level, the thicker the required rigid insulation thickness.

The core parameters for measuring the performance of Laminated inverter busbars insulation materials mainly include relative temperature index (RTI), relative leakage trace index (CTI), and elongation, which correspond to the material's heat resistance life, surface electrical properties, and mechanical compatibility, respectively.

RTI is defined according to UL 746 standard as the maximum continuous operating temperature of insulation materials, specifically the temperature at which the mechanical elongation and electrical breakdown strength of the material decrease to 50% of their initial values after 20000 hours of use. Actual test data shows that polyester materials can achieve a service life of 60000 hours at 105 ° C, and following Arrhenius' law, the service life will double or halve for every 10 ° C temperature change.

CTI mainly reflects the anti leakage and tracing ability of insulation material surfaces in polluted environments, directly determining the design of the creepage distance of Laminated busbar connectors in high-voltage applications, and is a key selection basis for voltage scenarios above 1000V. The elongation rate reflects the material's tensile resistance, with PET elongation rate ≥ 100%, much higher than PI's 70%. This characteristic makes it more adaptable in processes such as sealing and sealing molds.

In addition to mainstream flexible and rigid insulation materials, powder coating is also an important supplementary solution for Laminated bus bar for industrial conductor insulation, especially suitable for insulation treatment of single conductors with complex shapes. The powder spraying process can easily achieve sealing and protection of the entire surface of the conductor, solving the problem of epoxy resin coating being difficult to seal complex shaped conductors.

It should be noted that powder coating schemes are usually suitable for single conductors that do not come into direct contact with other conductors, so the insulation protection requirements for critical positions such as sharp corners of the conductor are relatively low. This feature makes it an economical choice for specific scenarios, enriching the selection system of Busbar for transformer insulation materials and meeting the insulation requirements of different structures and working conditions.

If you have any questions about the selection or parameter matching of Laminated copper busbar insulation materials, please feel free to contact us at any time. We will provide you with accurate insulation solution suggestions based on project conditions, helping your product achieve optimal electrical performance and reliability.