Patent US3720867A successfully refreshed from Google Patents.
US3720867A
Expired / Lapsed
US
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Fail safe vacuum type circuit interrupter and associated load current tap changer for electric induction apparatus
Assignee: General Electric Co
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Filing: 1972-02-04
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Granted: 1973-03-13
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Expires: 1992-02-04
Abstract
Abstract A load current tap changer for electric power transformers includes a vacuum type arcing-duty current interrupter immersed in dielectric fluid and biased to closed position by differential pressure. Overtravel limit switch means is actuated to shunt the vacuum arc gap upon excessive contact separation due to loss of vacuum and contact bias force. Limiting contact overtravel also disables the tap selector driving means.
Inventors
- 👤 W Rathbun
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 07:45
CPC Classifications
H; H01; H01H; H01H9/00; H01H9/0005; H01H9/0038; H01F; H01F27/00; H01F27/40; H01F27/402; H01F27/404; H01H33/00; H01H33/60; H01H33/66; H01H33/668
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
221 words
A load current tap changer for electrical apparatus having a plurality of tap terminals and a line terminal comprising, a pair of movable tap selector contacts mounted for sequential stepping movement in either direction between adjacent tap terminals, a pair of parallel branch circuits each connecting one of said tap selector contacts to said line terminal, each said branch circuit including a transfer switch having separable line and load contacts, a vacuum type circuit interrupting device connected between the load contacts of said transfer switches and including separable arcing contacts within an evacuated envelope, said arcing contacts being biased into engagement by differential pressure within and without said envelope, means actuating said transfer switches alternately to open position thereby to transfer said arcing contacts into one said branch circuit, means actuating said arcing contacts to normal disengaged positions separated by an arc gap thereby to interrupt current through said one branch circuit prior to stepping movement of the associated tap selector contact, said actuating means and at least one said arcing contact being free to overtravel beyond its normal disengaged position in response to abnormal increase of pressure within said envelope thereby to increase the length of said arc gap, and limiting contact means engageable upon predetermined overtravel and abnormal separation of said arcing contacts to conductively shunt said arc gap.
Claim 2
Dependent Claim
221 words
A load current tap changer for electrical apparatus having a plurality of tap terminals and a line terminal comprising, a pair of movable tap selector contacts mounted for sequential stepping movement in either direction between adjacent tap terminals, a pair of parallel branch circuits each connecting one of said tap selector contacts to said line terminal, each said branch circuit including a transfer switch having separable line and load contacts, a vacuum type circuit interrupting device connected between the load contacts of said transfer switches and including separable arcing contacts within an evacuated envelope, said arcing contacts being biased into engagement by differential pressure within and without said envelope, means actuating said transfer switches alternately to open position thereby to transfer said arcing contacts into one said branch circuit, means actuating said arcing contacts to normal disengaged positions separated by an arc gap thereby to interrupt current through said one branch circuit prior to stepping movement of the associated tap selector contact, said actuating means and at least one said arcing contact being free to overtravel beyond its normal disengaged position in response to abnormal increase of pressure within said envelope thereby to increase the length of said arc gap, and limiting contact means engageable upon predetermined overtravel and abnormal separation of said arcing contacts to conductively shunt said arc gap.
Claim 3
Dependent Claim
221 words
A load current tap changer for electrical apparatus having a plurality of tap terminals and a line terminal comprising, a pair of movable tap selector contacts mounted for sequential stepping movement in either direction between adjacent tap terminals, a pair of parallel branch circuits each connecting one of said tap selector contacts to said line terminal, each said branch circuit including a transfer switch having separable line and load contacts, a vacuum type circuit interrupting device connected between the load contacts of said transfer switches and including separable arcing contacts within an evacuated envelope, said arcing contacts being biased into engagement by differential pressure within and without said envelope, means actuating said transfer switches alternately to open position thereby to transfer said arcing contacts into one said branch circuit, means actuating said arcing contacts to normal disengaged positions separated by an arc gap thereby to interrupt current through said one branch circuit prior to stepping movement of the associated tap selector contact, said actuating means and at least one said arcing contact being free to overtravel beyond its normal disengaged position in response to abnormal increase of pressure within said envelope thereby to increase the length of said arc gap, and limiting contact means engageable upon predetermined overtravel and abnormal separation of said arcing contacts to conductively shunt said arc gap.
Claim 4
Dependent Claim
221 words
A load current tap changer for electrical apparatus having a plurality of tap terminals and a line terminal comprising, a pair of movable tap selector contacts mounted for sequential stepping movement in either direction between adjacent tap terminals, a pair of parallel branch circuits each connecting one of said tap selector contacts to said line terminal, each said branch circuit including a transfer switch having separable line and load contacts, a vacuum type circuit interrupting device connected between the load contacts of said transfer switches and including separable arcing contacts within an evacuated envelope, said arcing contacts being biased into engagement by differential pressure within and without said envelope, means actuating said transfer switches alternately to open position thereby to transfer said arcing contacts into one said branch circuit, means actuating said arcing contacts to normal disengaged positions separated by an arc gap thereby to interrupt current through said one branch circuit prior to stepping movement of the associated tap selector contact, said actuating means and at least one said arcing contact being free to overtravel beyond its normal disengaged position in response to abnormal increase of pressure within said envelope thereby to increase the length of said arc gap, and limiting contact means engageable upon predetermined overtravel and abnormal separation of said arcing contacts to conductively shunt said arc gap.
Claim 5
Dependent Claim
36 words
A tap changer according to claim 1 wherein said limiting contact means is mounted within said envelope and actuated to engaged position in response to predetermined abnormal overtravel of at least one of said arcing contacts.
Claim 6
Dependent Claim
58 words
A tap changer according to claim 1 wherein said limiting contact means comprises a cylindrical metal shield mounted within said envelope and enclosing said arc gap in coaxial radial spaced relation and a contact means actuated by at least one of said arcing contacts to engage said shield in response to abnormal overtravel of said one arcing contact.
Claim 7
Dependent Claim
68 words
A tap changer according to claim 3 wherein one said arcing contact is fixed and the other movable, normally fixed deformable mounting means electrostatically isolated from said arcing contacts positions said shield normally beyond engagement with either of said arcing contacts and said movable arcing contact is positioned to engage said shield upon abnormal overtravel contact movement and move said shield into engagement with said fixed arcing contact.
Claim 8
Dependent Claim
48 words
A tap changer according to claim 3 wherein one said arcing contact is fixed and the other movable, said shield is mounted upon and electrically connected to the fixed arcing contact, and conductive means on the movable arcing contact engages said shield upon predetermined abnormal contact opening movement.
Claim 9
Dependent Claim
60 words
A tap changer according to claim 1 wherein said arcing contacts comprise a pair of axially aligned conductive rods one of which is fixed to said envelope and the other is movably mounted upon a flexible wall portion of said envelope, and said limiting contact means comprises a fixed contact and a movable contact actuated by said movable contact rod.
Claim 10
Dependent Claim
18 words
A tap changer according to claim 6 wherein said limiting contact means is positioned outside said evacuated envelope.
Claim 11
Dependent Claim
32 words
A tap changer according to claim 1 additionally including driving means for actuating said tap selector contacts and means operable upon abnormal separation of said arcing contacts to disable said driving means.
Claim 12
Dependent Claim
39 words
A tap changer according to claim 8 wherein said driving means includes alternately and intermittently rotatable gearing connected to actuate said tap selector contacts and said disabling means comprises blocking means engageable positively to lock said gearing against movement.
Claim 13
Dependent Claim
32 words
A tap changer according to claim 8 wherein said driving means includes a rotatable electric motor and said disabling means comprises a clutch for disconnecting said motor from said tap selector contacts.
Claim 14
Dependent Claim
56 words
The combination with a tap changer according to claim 1 of an electric induction apparatus including said tap terminals and said line terminal, a common housing for said induction apparatus and said vacuum interrupting device, and a body of dielectric fluid in said housing at least partially immersing said induction apparatus and said vacuum interrupting device.
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) | 1976-03-12 | 1976-09-11 | 1977-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-12 | 1980-09-11 | 1981-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-12 | 1984-09-11 | 1985-03-13 | $7700.00 | Window Closed / Lapsed |