JST manufactures cast resin transformers with numerous advantages over other types of transformers (both oil-filled and VPI) and other cast resin transformers.

Technical advantages of cast resin transformers:

Lower cost of ownership than oil-filled

  • Less maintenance – Cast resin transformers don’t have oil that needs to be checked or refilled, or seals to replace.
  • Lower up-front construction costs – Cast resin transformers don’t need expensive catch basins.
  • Cheaper to decommission – Cast resin transformers contain no hazardous waste, and thus cost less to decommission.


  • Cast resin transformers are fire resistant – as opposed to oil-filled transformers, which are highly flammable and potentially very dangerous.
  • In the case of a short circuit, cast resin transformers won’t cause catastrophic damage. Because cast resin has better structural integrity, it will withstand a short circuit much better than oil-filled or VPI transformers.

Environmental Friendliness

  • Unlike oil-filled transformers, cast resin transformers contain no contaminants that could leak or otherwise escape into the environment.
  • Cast resin never requires expensive cleanup.


  • Cast resin is very efficient — equal to or greater than 98% — and especially more efficient than VPI.
  • Cast resin transformers are air-cooled, so they have considerably lower losses.

Advantages of JST’s transformers over other cast resin transformers:

  • JST uses the original “May-Christie” (barrel winding) design, which offers maximum efficiency.
  • During casting, we use a static mixing process. This results in better uniformity during curing, ensuring a higher degree of structural integrity in the final casting.
  • Our fan package uses a stainless steel squirrel cage air delivery system. JST’s fans give you 50% “additional capacity” — the highest in the business.

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