Skip to main content

What are Encapsulated Transformers and where are they used?

Encapsulated units are covered in a thicker coating of insulation than typical. Often the coils are completely encased in epoxy or an epoxy and aggregate mixture. Sometimes they are referred to as “potted” or “cast coil”.

The encapsulated design is especially suited for installations in harsh environments where dust, lint, moisture and corrosive contaminants are present. Typical applications include: pulp and paper plants; steel mills; food processing plants; breweries; mines; marine and shipboard installations.

  • What is the difference between impregnation and encapsulation

      Impregnation is the complete penetration of the process materials (generically called varnish or epoxy) into the windings of the transformers coils. This is often accomplished by using a Vacuum Pressure Impregnation (VPI) cycle.

      Encapsulation is the complete encasement by the process materials (generically called varnish or epoxy) onto the windings of the transformers coils. In simple terms, the process materials have a thicker, more complete coating than an impregnated transformer. Encapsulation can be done by performing two or more VPI cycles or using a higher viscosity process material. Sometimes “potted” will be used for “encapsulated”.  A Cast Coil transformer would be considered to be both impregnated and encapsulated.

      There is not an industry standard for encapsulation. A winding can be encapsulated, it can be impregnated or it can be encapsulated and impregnated.

  • What are Important Specifications for a Marine Duty Transformer?

      Marine Duty is often left to the manufacturer to define.  HPS provides American Bureau of Shipping (ABS) approved transformers which include:

      • Copper or aluminum windings
      • Dry-type convection-cooled
      • Standard NEMA taps
      • 150ºC, 115ºC or 80ºC temperature rise available
      • 220ºC, 200ºC or 180ºC insulation system available
      • VPI Impregnation for salt environments
      • Fungus resistant
      • Braced for marine applications
      • Enclosures:  NEMA 2 or NEMA 3R (per ABS requirements)
      • Stainless steel hardware (on units over 1000kVA)
      • UV protection for outdoor enclosures
      • UL50 frames, channels, etc.
      • CSA, UL and ABS approval (Lloyd’s Register and DNV approval available upon request)

  • What salt spray rating test have Hammond’s painted enclosures passed?
  • What are Encapsulated Transformers and where are they used?

      Encapsulated units are covered in a thicker coating of insulation than typical. Often the coils are completely encased in epoxy or an epoxy and aggregate mixture. Sometimes they are referred to as “potted” or “cast coil”.

      The encapsulated design is especially suited for installations in harsh environments where dust, lint, moisture and corrosive contaminants are present. Typical applications include: pulp and paper plants; steel mills; food processing plants; breweries; mines; marine and shipboard installations.

  • What does the term “Encapsulated” describe?

      A transformer with its coils either encased or cast in an epoxy resin or other encapsulating materials. This includes cast coil and potted transformers. Manufacturers may also consider transformers which go through multiple dip and bake cycles creating a thicker coating as encapsulated.