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Patent US4589048A successfully refreshed from Google Patents.
US4589048A
Expired / Lapsed
US
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Apparatus for detecting ground fault in variable-voltage variable-frequency power system
Assignee: Mitsubishi Electric Corp
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Filing: 1984-01-17
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Granted: 1986-05-13
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Expires: 2004-01-17
Abstract
Abstract An apparatus for detecting a ground fault occurring in a power system which furnishes an AC power from a variable-voltage variable-frequency power supply to a load via a voltage transformer. The apparatus compares a zero phase sequence current with a reference value and, upon detection of occurrence of a ground fault, produces an output signal representing the ground fault. Prior to such comparison, the zero phase sequence current is so processed as to be independent of the frequency of the power system or the reference value is so processed as to be dependent on the said frequency.
Inventors
- 👤 Nobuharu Takata
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:57
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/16; H02H3/162; G; G01; G01R; G01R27/00; G01R27/02; G01R27/16; G01R27/18; G01R31/00; G01R31/50; G01R31/52
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
100 words
An apparatus for detecting a ground fault in a power system which is fed with a variable-voltage, variable-frequency power source controlled in such manner that the output voltage of said power source is nearly proportional to its output frequency, said apparatus comprising: input means for producing a signal proportional to a zero phase sequence voltage or current of said power system; modifying means for obtaining an operation signal inversely proportional to the frequency of said power system from the signal of said input means; and relay means activated when the signal of said modifying means is beyond a predetermined level.
Claim 2
Independent Claim
100 words
An apparatus for detecting a ground fault in a power system which is fed with a variable-voltage, variable-frequency power source controlled in such manner that the output voltage of said power source is nearly proportional to its output frequency, said apparatus comprising: input means for producing a signal proportional to a zero phase sequence voltage or current of said power system; modifying means for obtaining an operation signal inversely proportional to the frequency of said power system from the signal of said input means; and relay means activated when the signal of said modifying means is beyond a predetermined level.
Claim 3
Dependent Claim
46 words
The ground fault detecting apparatus as defined in claim 1, wherein said modifying means comprises zero phase sequence current transformer and a capacitor connected across the terminals of the secondary winding of said current transformer, the voltage on said capacitor being introduced to said relay means.
Claim 4
Independent Claim
102 words
An apparatus for detecting a ground fault in a power system which is fed with a variable-voltage, variable-frequency power source controlled in such manner that the output voltage of said power source is nearly proportional to its output frequency, said apparatus comprising: first input means for producing an operation signal proportional to a zero phase sequence voltage or current of said power system; second input means for producing a reference signal proportional to the frequency of said power system; and relay means activated when the output signal of said first input means is beyond the reference signal of said second input means.
Claim 5
Independent Claim
102 words
An apparatus for detecting a ground fault in a power system which is fed with a variable-voltage, variable-frequency power source controlled in such manner that the output voltage of said power source is nearly proportional to its output frequency, said apparatus comprising: first input means for producing an operation signal proportional to a zero phase sequence voltage or current of said power system; second input means for producing a reference signal proportional to the frequency of said power system; and relay means activated when the output signal of said first input means is beyond the reference signal of said second input means.
Claim 6
Dependent Claim
37 words
The ground fault detecting apparatus as defined in claim 3, wherein said second input means comprises a pilot generator connected to said motor, and said reference signal is obtained from the output voltage of said pilot generator.
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) | 1989-05-12 | 1989-11-11 | 1990-05-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-05-12 | 1993-11-11 | 1994-05-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-05-12 | 1997-11-11 | 1998-05-13 | $7700.00 | Window Closed / Lapsed |