VPI dry-type transformers are designed with H and C class series materials such as Nomex®, Cequin, and Tufquin produced by companies like DuPont Quin-T, which have been certified by the Underwriters Laboratories (UL). These materials are used to create an insulation system with a temperature range of 180°C to 220°C. This system is self-extinguishing and flame-retardant, significantly enhancing operational safety. The coils are manufactured using the advanced VPI (Vacuum Pressure Impregnation) process, fully impregnated with UL-certified flame-retardant ET-90 series H-class modified heat-resistant polyester and resin. The resulting coating is uniform, transparent, has strong adhesion, does not crack, has low partial discharge, and offers excellent electrical performance and overall mechanical strength. It can operate safely in environments with high humidity, salt spray, and other forms of pollution, and has superior weather resistance. The coils adopt an open (non-encapsulated) structure with a scientifically designed air passage distribution, ensuring high heat dissipation efficiency, uniform temperature rise, reasonable margin, and strong overload capacity.
The H-class series OVDT products, with their advanced design, compact and reasonable structure, low loss, low partial discharge, and strong overload capacity, among other performance indicators and reliable safety features, are widely used in load centers with high requirements for fire safety and environmental protection, such as tourist attractions, high-rise buildings, airports, subways, stations, docks, hospitals, power plants, shopping centers, and residential areas.
Product Features of VPI Dry-Type Transformer
Excellent Environmental Friendliness: The insulation system is composed of NOMEX paper and other insulation materials certified by the U.S. UL (Underwriters Laboratories) with insulation grades of H1-C (180-220℃). It does not release toxic gases when decomposing at temperatures above 750℃. The high-voltage wires adopt a continuous structure with a thin insulation paint film. After the service life, the copper materials can be conveniently recycled without polluting the environment.
Advanced Processability and "Zero" Partial Discharge: The coils undergo multiple VPI (Vacuum Pressure Impregnation) processes and multi-stage baking and curing processes. The paint film penetrates thoroughly, evenly, and has strong adhesion. After forming, the surface is bright and crack-free, with "zero" partial discharge.
High Safety and Reliability: The insulation materials selected have insulation grades of H-C (180-220℃), are flame-retardant and self-extinguishing. After the VPI (Vacuum Pressure Impregnation) process and multi-stage baking and curing processes, the formed paint film not only provides protection for the insulation system but also improves the electrical performance of the wires.
Stable and Strong Overload Capacity: Through scientific optimization design and process guarantee, the temperature rise is uniformed, good heat dissipation conditions are obtained, and the heat dissipation efficiency is improved. It can operate at 120% of the rated capacity for a long time.
Reliable and Strong Short-Circuit Withstand Capacity: Advanced processes, special and effective spring and silicone rubber pad double pre-compression devices greatly enhance the mechanical performance of the coils and the transformer as a whole, avoiding stress concentration and improving the product's short-circuit resistance.
Low Loss and Low Noise: Low loss and noise requirements, high-quality materials, advanced processes, and strict process quality control effectively and reliably ensure the transformer's loss and noise.
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