US3904785A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for insulating electric armature windings
Assignee: General Electric Co
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Filing: 1974-01-11
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Granted: 1975-09-09
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Expires: 1994-01-11
Abstract
Abstract A method of insulating an electrical conductor, such as a stator winding for an electric motor, is provided wherein the conductor is immersed in a thermosetting epoxy resin and then is rapidly heated by passing a direct current of pre-determined magnitude through the conductor to establish a current density in it in the range of 8,000 to 30,000 amperes per square inch of conductor cross-section. The resultant resistant heating of the conductor and the epoxy resins closely adjacent thereto causes a layer of the resin to gel around the conductor. Heating current is continued until the gelled layer is 5 to 100 mils thick, at which point the current is interrupted and the conductor is withdrawn from the varnish. The final step in the disclosed method is to bake the gelled coating of resin to finally cure it and form a hard insulating finish on the conductor.
Inventors
- 👤 Frederick William Baumann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 19:33
CPC Classifications
B; B05; B05D; B05D1/00; B05D1/18; H; H01; H01B; H01B13/00; H01B13/06; H01B13/065
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
133 words
A METHOD OF INSULTING AN ELECTRICAL CONDUCTOR COMPRISING THE STEPS OF A. PROVING A BATH OF THERMOSETTING EPOXY VARNISH B. IMMERSING AN ELECTRICAL CONDUCTOR IN THE EPOXY VARNISH, C. PASSING AN ELECTRIC CURRENT THROUGH THE IMMERSED CONDUCTOR THEREBY TO ESTABLISH A CURRENT DENSITY IN THE RANGE OF 8,000 TO 30,000 AMPERES PER SQUARE INCH OF CONDUCTOR CRSS-SECTION IN THE CONDUCTOR TO RAPIDLY HEAT IT AND IT AND THE EPOXY VANISH CLOSELY ADJACENT THERETO, D. CONTINUING THE HEATING OPERATION OF STEPS (C) UNTIL A LAYER OF VANISH HAVING A THICKNESS IN THE RANGE OF 5 TO 100 MILS HAS GELLED ON SAID CONDUCTOR, E. DISCONTINUING THE PASSAGE OF CURRENT THROUGH THE CONDUCTOR AND REMOVING IT FROM THE BATH, AND F. CURING THE GELLED LAYER OF VARNISH TO FORM A HARD FINISH ON THE CONDUCTOR.
Claim 2
Independent Claim
133 words
A METHOD OF INSULTING AN ELECTRICAL CONDUCTOR COMPRISING THE STEPS OF A. PROVING A BATH OF THERMOSETTING EPOXY VARNISH B. IMMERSING AN ELECTRICAL CONDUCTOR IN THE EPOXY VARNISH, C. PASSING AN ELECTRIC CURRENT THROUGH THE IMMERSED CONDUCTOR THEREBY TO ESTABLISH A CURRENT DENSITY IN THE RANGE OF 8,000 TO 30,000 AMPERES PER SQUARE INCH OF CONDUCTOR CRSS-SECTION IN THE CONDUCTOR TO RAPIDLY HEAT IT AND IT AND THE EPOXY VANISH CLOSELY ADJACENT THERETO, D. CONTINUING THE HEATING OPERATION OF STEPS (C) UNTIL A LAYER OF VANISH HAVING A THICKNESS IN THE RANGE OF 5 TO 100 MILS HAS GELLED ON SAID CONDUCTOR, E. DISCONTINUING THE PASSAGE OF CURRENT THROUGH THE CONDUCTOR AND REMOVING IT FROM THE BATH, AND F. CURING THE GELLED LAYER OF VARNISH TO FORM A HARD FINISH ON THE CONDUCTOR.
Claim 3
Dependent Claim
34 words
A method as defined in claim 1 wherein the epoxy varnish is a catalyzed epoxy that is virtually inactive at temperatures lower than 80*C and is actively gelled at a temperature of about 120*C.
Claim 4
Dependent Claim
30 words
A method as defined in claim 2 wherein the heating operation of step (c) is continued for a pre-determined period of time in the range of 1/2 to 40 minutes.
Claim 5
Dependent Claim
26 words
A method as defined in claim 3 wherein the layer of gelled varnish is cured by baking the varnish at approximately 170*C for about 4 hours.
Claim 6
Dependent Claim
22 words
A method as defined in claim 1 wherein the conductor is formed into a coil before it is immersed in the varnish.
Claim 7
Dependent Claim
32 words
A method as defined in claim 5 wherein the coil is random wound and including the step of restraining the strands of the coil in a pre-determined configuration during the immersion thereof.
Claim 8
Dependent Claim
29 words
A method as defined in claim 6 wherein restraining the strands of the coil is effected by lap winding a layer of tape around the strands of the coil.
Claim 9
Dependent Claim
32 words
A method as defined in claim 5 wherein the layer of varnish formed to a hard finish on the conductor is capable of withstanding a voltage of 13 KV without being punctured.
Claim 10
Dependent Claim
79 words
A method as defined in claim 6 including a plurality of conductors wound in the method defined in claim 6 to form a plurality of coils and further including a cylindrically shaped magnetic core member for an electric motor, said core member being formed to have a plurality of arcuately spaced-apart winding-receiving slots around one of its circumferential surfaces, said plurality of coils being mounted in said slots prior to the immersion of the coils into the epoxy resin.
Claim 11
Dependent Claim
48 words
A method as defined in claim 9 wherein one side of at least two of said coils are disposed, respectively, in each of said slots, the respective strands of each of said coil sides being insulated from one another in said slots only by the epoxy varnish thereon.
Claim 12
Dependent Claim
57 words
A method as defined in claim 10 wherein the means for restraining the strands of the respective coils prior to immersion in the varnish comprises a layer of tape lap wound around the strands of each of the coils, and only the varnish impregnated tapes and varnish insulate the coil sides in each slot from one another.
Claim 13
Dependent Claim
28 words
A method as defined in claim 10 wherein the electric current applied to the coils of the motor windings to gel the varnish thereon is a direct current.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-08 | 1979-03-10 | 1979-09-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-08 | 1983-03-10 | 1983-09-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-08 | 1987-03-10 | 1987-09-09 | $7700.00 | Window Closed / Lapsed |