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Cast Coil Transformers



Suitable For Harsh Environments - Rex Power Magnetics' Cast Coil Type Transformers offer the greatest degree of protection against the presence of atmospheric pollutants effecting the performance and life expectancy of the transformer.

High Short Circuit Strength - The fiberglass reinforced solid cast construction provides superior mechanical strength with the highest short circuit withstand capability of all types of transformers.

High Overload Capability - Due to the longer thermal time constant in comparison with ventilated Dry Type Transformers higher short time overload capabilities are possible with our Cast Coil Transformers.

Environmentally Friendly - Rex Cast Coil Transformers contain only chemically non-hazardous materials.

High Impulse Voltage Strength - The impulse voltage withstand capability of Cast Coil Transformers is higher than conventional dry type and is comparable to liquid filled transformers.

Maintenance And Resistance To Temperature Fluctuations - Rex Cast Coil Transformers are virtually maintenance free due to their smooth, crevice free construction. Cast Coil Transformers can be installed at ambient temperatures as low as -50°C and can be energized from cold starts at full rated load.

  • Unparalleled performance in polluted & harsh environments
  • High impulse voltage withstand
  • Environmentally safe
  • Exceptionally high short circuit strength
  • High overload capability
  • High resistant to temperature fluctuations
  • Non-flamable and self extentinguishing
  • Completely cast and assembled in North America

Design and Construction Features

  1. The primary and secondary windings are magnetically and electrical balanced to minimized mechanical stresses due to short circuit and momentary overloads, especially due to axial forces.
  2. Unique coil construction techniques are utilized to reduce the dielectric stresses due to uneven distribution during impulse. The dielectric stresses are such that partial discharges are virtually non-existent at 120% over voltage.
  3. The Epoxy used in casting the coils, is a two-part very low viscosity filled resin, giving the perfect balance between the penetration capabilities and thermal shock performance. Extensive use of fiberglass reinforcement wraps in the coil construction further enhances the strength and crack resistance of the finished coils.
  4. Conductor and inter-layer insulation used in the coil construction are aramid paper (Nomex) and the casting resin is based on an Epoxy approved for use in 185oC Class system.
  5. Each coil is preheated in its casting mold that is specifically designed to withstand vacuum. The preheated mixed Epoxy is then introduced under high vacuum into the mold. The procedure of pulling vacuum directly into the mold was specifically developed by us and ensures the greatest penetration and most void free casting possible. The filled mold is then subjected to a programmed pre-baked, baked and post-baked cycle, which can last from 16 to 30 hours to relieve the casting of all residual stresses before removing the finished coil from the mold.
  6. The primary and secondary coils are cast separately and assembled coaxially on the core with special axial clamping techniques giving uniform pressure while allowing for thermal expansion and ensuring maximum creepage distance between the coils.

How do cast coil transformers compare?

  • Cast Coil Transformers are ideal for use in installations where environmental restrictions discourage the use of liquid filled units.
  • Cast Coil Transformers require very little maintenance in comparison to liquid filled transformers, which require regular maintenance to check gauge levels and periodically sample test of cooling liquids. Low maintenance type transformers are preferred in harsh environments where regular maintenance routines are difficult or uncomfortable to perform.
  • The initial equipment cost of Cast Coil Type Transformers is comparable to silicon fill units and is higher than the cost of conventional Dry Type or mineral oil fill transformers. Although the equipment cost is marginally higher, the installation cost of Cast Coil Transformers is similar to that of conventional dry type units and significantly lower than liquid filled units.
  • Rex Cast Coil Transformers are as adaptable as conventional Dry Type Transformers allowing for easier coordination with other equipment compared to typical liquid filled units.
  • Rex Cast Coil Transformers are designed with a long thermal time constant. The results in a transformer with higher short-term overload capabilities.
  • The solid epoxy, fiberglass reinforced cast construction produces coils that have outstanding mechanical strength which results in unparalleled short circuit withstand capability. This high short circuit withstand and short term over load capabilities of our Cast Coil Transformers make them ideal for heavy industrial installations such as automotive manufacturing, rapid transit and traction power applications.

 * Information is subject to change without prior notice