Engineering · Dry-type
Where cast resin transformers fit in industrial projects
Published 4 November 2026 by Jaybee Industries
Cast resin transformers encapsulate the windings in epoxy resin and use no oil. That one difference changes where they can be installed and how they are maintained. Jaybee built its first cast resin units in 2023 and in 2026 became the first approved manufacturer of cast resin dry-type transformers. Its dry-type range covers cast resin and VPI from about 16 kVA to 5 MVA.
Good fits
- Pharma and FMCG blocks in Haridwar SIDCUL or Selaqui, where the substation sits inside or beside production buildings
- Hospitals and institutions in Dehradun, Jammu and Srinagar, where oil indoors is not acceptable
- Tunnels, underground and enclosed infrastructure, where fire load and oil containment are hard to manage
- Commercial buildings with basement substations
Where oil-filled still makes sense
For outdoor yards with space for oil containment and higher ratings, especially power transformers at 33–66 kV, oil-filled designs remain the norm. Jaybee's oil vs dry-type comparison sets out the trade-offs.
What to specify for a cast resin unit
- Rating, HV/LV, vector group and impedance
- Indoor room size and ventilation, or the enclosure IP rating
- Insulation class and temperature rise
- Cooling: natural air (AN), or with fans (AF) for extra capacity
- Altitude and ambient (relevant in hill and valley sites)
- Temperature monitoring and alarm/trip requirements
Cast resin vs VPI
Both are dry-type. Cast resin fully encapsulates the windings and is usually preferred for harsher or humid environments. VPI impregnates the windings with varnish under vacuum and pressure. Your consultant's specification usually decides which, and Jaybee can quote either.