Patent US3955168A successfully refreshed from Google Patents.
US3955168A
Expired / Lapsed
US
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Rejuvenation method for varistors
Assignee: General Electric Co
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Filing: 1974-09-03
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Granted: 1976-05-04
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Expires: 1994-09-03
Abstract
Abstract A method of rejuvenating polycrystalline metal oxide varistors whose performance characteristics may have been degraded by prolonged voltage stress is disclosed. The method includes removing voltage stress from the varistors and heating the varistors.
Inventors
- 👤 Lionel M. Levinson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 18:02
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/10; H01C7/105; H01C7/108
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
53 words
A method of rejuvenating polycrystalline metal oxide varistors comprising the steps of: removing a voltage stress from polycrystalline metal oxide varistors whose leakage current performance has been degraded by prolonged exposure to said voltage stress and heating said varistors in the absence of said voltage stress until said leakage current performance is rejuvenated.
Claim 2
Independent Claim
53 words
A method of rejuvenating polycrystalline metal oxide varistors comprising the steps of: removing a voltage stress from polycrystalline metal oxide varistors whose leakage current performance has been degraded by prolonged exposure to said voltage stress and heating said varistors in the absence of said voltage stress until said leakage current performance is rejuvenated.
Claim 3
Dependent Claim
32 words
The method of claim 1 wherein said heating step more particularly comprises heating said varistors to a greater temperature than the temperature at which said varistors operated with said voltage stress applied.
Claim 4
Dependent Claim
22 words
The method of claim 2 wherein said heating step more particularly comprises holding said greater temperature constant for a period of time.
Claim 5
Independent Claim
61 words
A method of rejuvenating polycrystalline metal oxide varistors comprising the steps of: removing a voltage stress from polycrystalline metal oxide varistors whose leakage current performance has been degraded by prolonged exposure to said voltage stress; heating said varistors to a temperature between 120°C and 150°C; and holding said varistors at said temperature for a period between 40 hours and 60 hours.
Claim 6
Independent Claim
61 words
A method of rejuvenating polycrystalline metal oxide varistors comprising the steps of: removing a voltage stress from polycrystalline metal oxide varistors whose leakage current performance has been degraded by prolonged exposure to said voltage stress; heating said varistors to a temperature between 120°C and 150°C; and holding said varistors at said temperature for a period between 40 hours and 60 hours.
Claim 7
Dependent Claim
14 words
The method of claim 4 further including the step of: repeating said method periodically.
Claim 8
Dependent Claim
11 words
The method of claim 5 wherein said method is repeated annually.
Claim 9
Dependent Claim
27 words
The method of claim 4 wherein said varistors are contained in a conduit and said heating step more particularly comprises blowing a heating fluid through said conduit.
Claim 10
Dependent Claim
28 words
The method of claim 7 further including the step of blowing a cooling fluid through said conduit while applying said voltage stress for normal operation of said varistors.
Claim 11
Independent Claim
62 words
A method of rejuvenating polycrystalline metal oxide varistors comprising the steps of removing a voltage stress from polycrystalline metal oxide varistors, which varistors are contained in a conduit, whose leakage current performance has been degraded by prolonged exposure to said voltage stress; and blowing a heating fluid through said conduit, whereby said varistors are heated in the absence of said voltage stress.
Claim 12
Independent Claim
62 words
A method of rejuvenating polycrystalline metal oxide varistors comprising the steps of removing a voltage stress from polycrystalline metal oxide varistors, which varistors are contained in a conduit, whose leakage current performance has been degraded by prolonged exposure to said voltage stress; and blowing a heating fluid through said conduit, whereby said varistors are heated in the absence of said voltage stress.
Claim 13
Independent Claim
176 words
A method for operating a plurality of polycrystalline metal oxide varistors contained in a single enclosure comprising the steps of: operating normally a first set of varistors of a plurality of varistors with voltage stress applied thereto while not applying voltage stress to a second set of varistors of said plurality of varistors for a preselected period of time; switching said voltage stress from said first set of varistors to said second set of varistors and operating normally said second set of varistors for said preselected period of time; periodically switching said voltage stress between said first set of varistors and said second set of varistors; applying heat to varistors in said first set at such times as voltage stress is not applied to said varistors in said first set; and applying heat to varistors in said second set at such times as voltage stress is not applied to said varistors in said second set; whereby leakage current performance in said varistors, whose performance has been degraded by prolonged exposure to said voltage stress, is rejuvenated.
Claim 14
Independent Claim
176 words
A method for operating a plurality of polycrystalline metal oxide varistors contained in a single enclosure comprising the steps of: operating normally a first set of varistors of a plurality of varistors with voltage stress applied thereto while not applying voltage stress to a second set of varistors of said plurality of varistors for a preselected period of time; switching said voltage stress from said first set of varistors to said second set of varistors and operating normally said second set of varistors for said preselected period of time; periodically switching said voltage stress between said first set of varistors and said second set of varistors; applying heat to varistors in said first set at such times as voltage stress is not applied to said varistors in said first set; and applying heat to varistors in said second set at such times as voltage stress is not applied to said varistors in said second set; whereby leakage current performance in said varistors, whose performance has been degraded by prolonged exposure to said voltage stress, is rejuvenated.
Claim 15
Dependent Claim
14 words
The method of claim 10 wherein the period of said periodic switching is annual.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-05-04 | 1979-11-03 | 1980-05-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-05-04 | 1983-11-03 | 1984-05-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-05-04 | 1987-11-03 | 1988-05-04 | $7700.00 | Window Closed / Lapsed |