Method for making a transformer

Details Method for making a transformer Method for making a transformer

1998-02-17

2001-02-13

Martin-Wallace, Valencia (Department: 3713)

Metal working

Method of mechanical manufacture

Electrical device making

C029S602100, C029S603040, C029S603250, C336S055000, C336S061000, C336S096000, C336S198000, C336S205000

Reexamination Certificate

active

06185811

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the transformer art. More particularly, the present invention pertains to the art and science of transformer structures and methods for constructing those structures. Even more specifically, the present invention relates to a transformer with an impregnated core and coil assembly and a molded outer coating that encapsulates the core and coil assembly to provide improved performance characteristics, while reducing size and cost associated with prior designs.
BACKGROUND OF THE INVENTION
Heretofore, transformers in commercial settings half typically comprised a transformer core assembly having a primary and secondary windings coupled with a laminated iron core element, typically in an E-shaped configuration. During operation, essentially all of the energy dissipated in a conventional transformer appears as heat that is generated primarily by the transformer windings and core. Such heat increases the temperature of the windings and core, and thus, reduces the efficiency of the transformer. To operate the transformer in the safe temperature limit for the rated output capacity, the heat generated in the transformer in the form of losses must be carried away to the cooling medium which is air.
Prior attempts have been made in this field without adequately resolving the above-mentioned problems. For example, Spindler, U.S. Pat. No. 2,947,957, provides a transformer with spaced metallic cooling fins for thermally conducting heat generated by the core and coil. The cooling fins are secured to the core of the transformer via retaining screws. When the transformer is assembled, the entire assembly is dipped in a thermally conductive potting compound to increase the ruggedness and dissipation of heat from the windings. This design, however, is larger than conventional transformer designs with its protruding fins while not completely solving the problems associated with heat losses.
Other prior transformer designs have attempted to address the heat dissipation deficiencies generally associated with the prior art systems discussed above. One such attempt is found in Herbst, U.S. Pat. No. 2,948,930, for a heat conductive potting compound which is used to conduct heat from a transformer. This system, like the others discussed above, fails to satisfactorily overcome the operating deficiencies noted above, and further represents a somewhat bulky transformer design.
Still other designs have employed the use of a premolded shell that surrounds the internal components of the transformer. In particular, the shell is placed over the transformer coil and is glued to the transformer core. The shell is then filled with a liquid epoxy resin that is heated and cured. The premolded shell of these configurations, however, creates a heat dissipation interface that actually interferes with the heat transfer of the core and windings. Accordingly, these designs likewise fail to totally address the heat transfer requirements of the core and windings of the transfer.
SUMMARY OF THE INVENTION
Thus, the prior art transformer designs now offer unsatisfactory performance, at high cost with resulting efficiency losses from undue heat dissipation, particularly in a commercial setting. Accordingly, a principle object of the present invention is to generally overcome deficiencies of the prior art.
More particularly, it is an object of the present invention to provide a commercial quality transformer design that provides increased efficiency in operation.
It is another object of the present invention to provide a transformer design with improved heat transfer characteristics.
In addition, it is an object of the present invention to provide a transformer that is a compact design to address limited size requirements.
The present invention meets these and other additional objects through an improved transformer design. The invention improves the heat transfer from a source to a cooling medium such as the ambient by effectively conducting heat from the source to heat dissipating surfaces, and effectively increasing the heat dissipating surface area for a given volume. The present invention further provides a method for forming the same invention to achieve the desired result. Structurally, a preferred embodiment of the present invention comprises an inner coil and core assembly including a coil having a primary winding and a secondary winding, a core element with at least a portion extending through the coil, and terminals electrically coupled with the coil to provide access with the transformer. The core and coil assembly is impregnated with a material having a high thermal conductivity that bonds the components of the core assembly into a core mass.
An outer thermally conducting coating encapsulates the inner core mass to provide exterior heat transfer surfaces to the cooling media of air or liquid. The outer coating includes a plurality of molded fins for increasing the heat transfer area to the cooling medium thereby increasing the output rating of the transformer per unit size and the overall efficiency of operation. In this way, heat is transferred from the heat dissipating surfaces to a cooling media such as the ambient through radiation and conduction.
In another aspect of the present invention, a method for forming a transformer that includes a core assembly with a coil, a core element with a portion extending through the coil, and electrical terminals connected to the coil to provide electrical connection for the transformer. The method includes impregnating the core assembly with a material of high thermal conductivity to form a substantially unitary core mass. The impregnating step preferably uses vacuum pressure for removing moisture and other impurities from the core assembly such that the material fills the interstices of the core assembly. Thereafter, a thermally conductive coating is molded around the core assembly to encapsulate the core mass. Preferably, this molding step includes forming a plurality of finned surfaces proximate the coil of the inner core mass to provide improved heat transfer from the coil. Additional features and embodiments are described below.


REFERENCES:
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