US4667262A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Device for detecting a ground fault in the rotor winding of an electric machine
Assignee: BBC Brown Boveri AG Switzerland
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Filing: 1984-06-12
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Granted: 1987-05-19
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Expires: 2004-06-12
Abstract
Abstract In the invention, a ground current, impressed, in the case of a ground fault, by an offset-voltage source connected into an earth line and capacitively coupled to the rotor winding, is detected both in the ground line and in the exciter circuit via at least one current transformer which is preferably constructed as a ring-core transformer. By suitable summing of the ground current flowing in the ground line with that flowing in the exciter circuit, an indication is achieved which is selective with respect to the location of the ground fault in the exciter circuit.
Inventors
- 👤 Franz Maier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 15:08
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/34; G01R31/346; H; H02; H02H; H02H3/00; H02H3/16; H02H3/17; H02H7/00; H02H7/06; H02H7/065
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
159 words
A device detecting a ground fault in the rotor winding of an electric machine comprising: an exciter source; a source line connecting said exciter source with one end of said rotor winding; a return line connecting said exciter source with another end of said rotor winding; a current transformer the primary side of which includes said source line and said return line, and the secondary side of which includes a relay, electric current in said source line and said return line causing a zero net magnetic flux in said current transformer in the absence of a ground fault; a capacitor; an alternating voltage source; and a ground line connecting said rotor winding, said capacitor and said alternating voltage source in series to ground; said current transformer including said ground line as a primary winding so that, with a ground fault in the rotor winding a non-zero net magnetic flux is caused in said current transformer to actuate said relay.
Claim 2
Independent Claim
159 words
A device detecting a ground fault in the rotor winding of an electric machine comprising: an exciter source; a source line connecting said exciter source with one end of said rotor winding; a return line connecting said exciter source with another end of said rotor winding; a current transformer the primary side of which includes said source line and said return line, and the secondary side of which includes a relay, electric current in said source line and said return line causing a zero net magnetic flux in said current transformer in the absence of a ground fault; a capacitor; an alternating voltage source; and a ground line connecting said rotor winding, said capacitor and said alternating voltage source in series to ground; said current transformer including said ground line as a primary winding so that, with a ground fault in the rotor winding a non-zero net magnetic flux is caused in said current transformer to actuate said relay.
Claim 3
Independent Claim
201 words
A device detecting a ground fault in the rotor winding of an electric machine comprising: an exciter source; a source line connecting said exciter source with one end of said rotor winding; a return line connecting said exciter source with another end of said rotor winding; a first current transformer the primary side of which includes said source line and said return line, electric current in said source line and said return line causing a zero net magnetic flux in said first current transformer in the absence of a ground fault; a capacitor; an alternating voltage source; a ground line connecting said rotor winding, said capacitor and said alternating voltage source in series to ground; a second current transformer the primary side of which includes said ground line, secondary sides of said first current transformer and said second current transformer connected in parallel and having a common circuit leg; and a relay connected in said common circuit leg, said first current transformer and said second current transformer generating an electric current in said common circuit leg in the presence of a ground fault in said rotor winding, said relay operating in response to said electric current in said common circuit leg.
Claim 4
Independent Claim
201 words
A device detecting a ground fault in the rotor winding of an electric machine comprising: an exciter source; a source line connecting said exciter source with one end of said rotor winding; a return line connecting said exciter source with another end of said rotor winding; a first current transformer the primary side of which includes said source line and said return line, electric current in said source line and said return line causing a zero net magnetic flux in said first current transformer in the absence of a ground fault; a capacitor; an alternating voltage source; a ground line connecting said rotor winding, said capacitor and said alternating voltage source in series to ground; a second current transformer the primary side of which includes said ground line, secondary sides of said first current transformer and said second current transformer connected in parallel and having a common circuit leg; and a relay connected in said common circuit leg, said first current transformer and said second current transformer generating an electric current in said common circuit leg in the presence of a ground fault in said rotor winding, said relay operating in response to said electric current in said common circuit leg.
Claim 5
Independent Claim
25 words
A device according to one of claims 1 or 2, wherein the relay is preceded in the circuit of the secondary by a low-pass filter.
Claim 6
Dependent Claim
16 words
A device according to claim 1, wherein the current transformer is constructed as a ring-core transformer.
Claim 7
Dependent Claim
43 words
A device according to claim 2, wherein the first and the second transformer are each provided with a transformer core, the transformer cores of said first and second transformers and the secondary windings of said first and second transformers being substantially identical, respectively.
Claim 8
Dependent Claim
26 words
A device according to claim 3, wherein a second relay is provided which is connected in parallel with a ground resistor connected in the ground line.
Claim 9
Dependent Claim
21 words
A device according to claim 6, wherein the second relay is preceded in the secondary side by a second low-pass filter.
Claim 10
Dependent Claim
17 words
A device according to claim 2 wherein the first and second transformers are constructed as ring-core transformers.
Claim 11
Dependent Claim
27 words
A device according to claim 1 and further including a dual change-over switch arranged so that the effective winding direction of the ground line can be reversed.
Claim 12
Dependent Claim
27 words
A device according to claim 1 and further including a single change-over switch arranged so that the number of turns of the ground line can be changed.
Claim 13
Dependent Claim
21 words
A device according to claim 2, wherein the relay is preceded in the circuit of the secondary by a low-pass filter.
Claim 14
Dependent Claim
26 words
A device according to claim 11, wherein a second relay is provided which is connected in parallel with a ground resistor connected in the ground line.
Claim 15
Dependent Claim
21 words
A device according to claim 12, wherein the second relay is preceded in the secondary side by a second low-pass filter.
Claim 16
Dependent Claim
53 words
A device according to claim 13 and further including a dual change-over switch arranged so that the effective winding direction of one of the following can be reversed: the ground line in the second current transformer, the secondary winding of the first current transformer, and the secondary winding of the second current transformer.
Claim 17
Dependent Claim
53 words
A device according to claim 13 and further including a single change-over switch arranged so that the number of turns of one of the following can be changed: the ground line in the second current transformer, the secondary winding of the first current transformer, and the secondary winding of the second current transformer.
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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) | 1990-05-18 | 1990-11-17 | 1991-05-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-05-18 | 1994-11-17 | 1995-05-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-05-18 | 1998-11-17 | 1999-05-19 | $7700.00 | Window Closed / Lapsed |