Encapsulated transformer

• US 5,589,808 A
• Filed: 08/12/1994
• Issued: 12/31/1996
• Est. Priority Date: 07/28/1993
• Status: Expired due to Term

• Current Assignee: Cooper Industries, Inc. (Eaton Corporation PLC.)
• Original Assignee: Cooper Industries, Inc. (Eaton Corporation PLC.)
• Inventors: Clark, William A., Strickland, Carl C. Jr., Newman, Mark C.
• Primary Examiner(s): Kozma, Thomas J.
• Application Number:
  US08/289,534
• Time in Patent Office: 872 Days
• Field of Search: 336/96, 336/205, 336/192, 336/198, 336/92, 336/229, 336/208
• US Class Current: 336/92
• CPC Class Codes: B29C 45/14639 for obtaining an insulating effect, e.g. for electrical components
• CPC Class Codes: B29C 45/34 having venting means
• CPC Class Codes: H01F 27/022 Encapsulation
• CPC Class Codes: H01F 41/005 Impregnating or encapsulating insulating of windings H01F41/12
• CPC Class Codes: Y10S 425/812 Venting

Abstract

An encapsulated transformer includes a transformer coil assembly, a rigid core insert having an upstanding portion positioned within the hollow interior of the core and a base portion on which the core rests, and a thermoplastic rubber jacket that completely surrounds the transformer coil assembly and is bonded to the base portion of the core insert to provide a completely waterproof encapsulated transformer which is impervious to liquid and gasses that could be detrimental to the performance of the transformer. A method for producing such an encapsulated transformer includes placing a rigid core insert in a mold cavity of a mold, and positioning a transformer coil assembly in the mold cavity so that the transformer coil assembly rests on the core insert. Thermoplastic rubber is then injected into the mold cavity to completely encapsulate the transformer coil assembly in a jacket of thermoplastic rubber. During the injection step, gas in the mold cavity is vented through a vent space provided in the bottom surface of the mold cavity. A mold for encapsulating a transformer coil assembly in thermoplastic rubber includes a bottom mold portion having a mold cavity, an upstanding pin disposed within the mold cavity, a mold cover for closing the mold cavity, and a vent space positioned in the bottom surface of the mold cavity for venting gas within the mold cavity to the exterior of the mold during the injection of thermoplastic rubber into the mold cavity.

Claims

1. An encapsulated transformer, comprising:

a transformer coil assembly that includes a core having a hollow interior, primary wire windings and secondary wire windings;

at least one primary lead connected to the primary windings;

at least one secondary lead connected to the secondary windings;

a rigid core insert having an upstanding portion positioned within the hollow interior of the core and a base portion on which the transformer coil assembly rests, said core insert having a hole which extends through the base portion and into the upstanding portion wherein the base portion of said core insert has an end face which faces away from said upstanding portion, said end face having at least one groove formed therein that extends from the hole in the core insert to an outer edge of the end face to communicate the hole in the core insert with the outer edge of the end face;

a unitary thermoplastic rubber jacket surrounding the transformer coil assembly and bonded to the base portion of the core insert to provide a completely waterproof encapsulated transformer.

2. The encapsulated transformer according to claim 1, wherein said upstanding portion of the core insert has an outer peripheral surface that is provided with a plurality of spaced apart grooves extend longitudinally along the upstanding portion, said thermoplastic rubber being disposed in the grooves.

3. The encapsulated transformer according to claim 1, wherein said base portion of said core insert has an outer periphery defined by a plurality of angularly oriented outer peripheral surface portions.

4. The encapsulated transformer according to claim 1, wherein said rigid core insert is fabricated of fiber-filled plastic material.

5. The encapsulated transformer according to claim 4, wherein said plastic material is polypropylene and said thermoplastic rubber jacket is made of a polypropylene based material.

6. The encapsulated transformer according to claim 1, wherein the base portion of said core insert has an end face which faces away from said upstanding portion, said end face having a first surface area defined by a diameter of the end face, said transformer coil assembly having a second surface area defined by a diameter of one end face of the core, the ratio of said second surface area to said first surface area being equal to or less than about 5:

1.

7. The encapsulated transformer according to claim 1, wherein said at least one primary lead and said at least one secondary lead extend outside the jacket and are each provided with a casing of thermoplastic rubber, said casing of thermoplastic rubber on the at least one primary lead and the casing of thermoplastic rubber on the at least one secondary lead being bonded to the thermoplastic rubber jacket.

8. The encapsulated transformer according to claim 7, wherein the jacket is made of the same thermoplastic rubber as the casing on the at least one primary lead and the casing on the at least one secondary lead.

9. The encapsulated transformer according to claim 1, wherein said at least one groove in said end face comprises two grooves formed therein that each extend from the hole in the core insert to an outer edge of the end face to communicate the hole in the core insert with the outer edge of the end face.

10. The encapsulated transformer according to claim 9, wherein said two grooves are positioned on diametrically opposite sides of the hole in the core insert.