Cushioning materials and method for applying the same to resin cast transformers
View Patent ↗A resin cast transformer having a core covered by a cushioning material is provided. The cushioning material is in contact with the core and includes a force absorption layer adjoining a force distribution layer. The force distribution layer is harder than the force absorption layer.
1. A transformer comprising:
a metal core;
primary and secondary windings disposed around the core;
a cushioning material in contact with the core and disposed between the core and the secondary winding, said cushioning material comprising a force absorption layer adjoining a force distribution layer, said force distribution layer being thinner and harder than said force absorption layer and being comprised of non-metallic material, and said force absorption layer being in contact with the core; and
a dielectric resin encapsulating the core, the primary and secondary windings and the cushioning material.
2. The transformer of claim 1 , wherein the force distribution layer and the force absorption layer are composed of different materials.
3. The transformer of claim 2 , wherein the force distribution layer is comprised of a web of cellulosic material.
4. The transformer of claim 3 , wherein the web of cellulosic material is pressboard.
5. The transformer of claim 3 , wherein the force absorption layer is comprised of a polymeric foam.
6. The transformer of claim 5 , wherein the polymeric foam is a closed cell thermoset polymer foam.
7. The transformer of claim 5 , wherein the dielectric resin comprises an epoxy resin.
8. The transformer of claim 2 , wherein the force distribution layer is in contact with the secondary winding.
9. The transformer of claim 2 , wherein the transformer is an instrument transformer.
10. The transformer of claim 2 , wherein the core is annular and the secondary winding is wound over the cushioning material and around the core.
11. The transformer of claim 10 , wherein the primary winding is annular and is interlinked with the core.
12. The transformer of claim 11 , wherein the force distribution layer is comprised of a web of cellulosic material and the force absorption layer is comprised of a polymeric foam.
13. The transformer of claim 2 , wherein the force absorption layer is secured to the force distribution layer by adhesive.
14. The transformer of claim 2 , wherein the cushioning material is disposed between the core and the primary winding.
15. The transformer of claim 2 , wherein the core is rectangular and includes an inner leg disposed between a pair of outer legs, and wherein the primary and secondary windings are mounted to the inner leg.
16. The transformer of claim 15 , wherein the force distribution layer is comprised of a web of cellulosic material and the force absorption layer is comprised of a polymeric foam.