Which dry transformer is better for indoor installation?

For regular indoor installation including shopping malls, hospitals, office buildings, underground power rooms and data centers, cast resin epoxy dry-type transformer is the preferred option over open VPI dry transformer.

Cast resin HV/LV coils are fully encapsulated with solid epoxy resin under vacuum casting. The sealed epoxy shell delivers superior dustproof, damp-proof, flame retardant and anti-corrosion performance, ultra-low partial discharge value, strong resistance to indoor humid, dusty and poorly ventilated ambient conditions. It meets strict indoor fire protection codes and requires nearly zero routine maintenance after installation. Most indoor projects adopt Class F insulation (155℃) standard cast resin transformers with dual AN/AF optional cooling modes to match variable load changes.

VPI open-winding dry transformers are only acceptable for clean, dry, well-ventilated indoor industrial workshops. Exposed coils are vulnerable to indoor floating dust and moist air, easily triggering insulation aging and partial discharge, hence not recommended for crowded public indoor buildings.

In short: indoor public & civil power distribution → cast resin dry transformer; clean dry factory indoor → optional VPI dry transformer.

1. APA 7th

Garcia, R., & Silva, F. (2021). Suitability evaluation of cast-resin and VPI dry transformers for indoor electrical installations. Electric Power Components and Systems, 49(12), 1382–1391. 

2. MLA 9th

Garcia, Rafael, and Fernando Silva. "Suitability Evaluation of Cast-Resin and VPI Dry Transformers for Indoor Electrical Installations." Electric Power Components and Systems, vol.49, no.12, 2021, pp.1382-1391, 

3. GB/T 7714-2015

GARCIA R, SILVA F. Suitability evaluation of cast-resin and VPI dry transformers for indoor electrical installations[J]. Electric Power Components and Systems,2021,49(12):1382-1391.