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Cast Coil Transformers

The cast coil transformer is a low-noise, low-loss, cast resin dry-type transformer. The high-voltage (HV) winding with copper conductors and the low-voltage (LV) winding with either copper conductors or copper sheet are wound and reinforced by glass-fiber and then cast with resin under vacuum.


The transformers have the following characteristics:

  • Windings have high mechanical strength and no partial discharge.
  • Epoxy resin and insulating materials used for windings are non-flammable, will not burn from an electric arc, and no toxic gases will be given off when the resin is burned.
  • Envionmental adaptability with windings that will not absorb moisture and a special anti-rust protective coating that seals the core and frame.
  • Operates under one-hundred percent relative humidity and other severe ambient conditions.
  • Ability to switch on the device without pre-drying or long periods of service interruptions.
  • Excellent short-circuit and lighting impulse strength.
  • Cooled naturally by air (AN) and forced air cooling (AF) provided as an option to improve overload capacity.
  • Smaller dimensions, less weight, and space saving.
  • Oil drainage pits and fire extinguishing devices not required for operation.
  • Customized Designs: To meet the needs of each unique application, specialized designs can be developed for our single phase, isolation, rectifier, and grounding transformers. In addition, customized tapping arrangements can also be provided.
Technical Soecifications
Voltage level 10-35 kV
Power capacity 30-20000 kVA
Type of voltage regulation off-circuit or on-load
Tapping range 5%, 2 +/- 2.5% (or as requested)
Frequency 50Hz or 60 Hz
Phases Three phase
Connection symbol Y yno; Dyn11 (or as requested)
Maximum temperature rise 100 oC
Cooling method AN or AF