US3904940A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Means for detecting ground insulation failure for rotary electric machines
Assignee: Allis Chalmers Corp
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Filing: 1974-10-10
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Granted: 1975-09-09
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Expires: 1994-10-10
Abstract
Abstract Electrical potentials are induced in the rotating shaft of many rotary electrical machines because of stray flux that exists in the machines. Unless provided with adequate ground insulation to interrupt the circuit, currents can flow through the machine bearings and other parts to ground and thereby expose the machine to severe damage. The device of this invention measures the voltage across the shaft and the bearing to indicate if there is a circuit for excessive current leakage from the bearing to ground.
Inventors
- 👤 Joe H Burrus
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:09
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/16; G01R27/18; G01R31/00; G01R31/34; G01R31/343
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
111 words
In combination with a dynamoelectric machine having an electrically grounded rotating shaft with electrical potential generated therein, a bearing rotatably supporting said shaft on a film of oil, said oil providing electrical insulation between said shaft and said bearing sufficient to cause a voltage potential across said oil film and electrical insulation isolating said bearing from electrical ground, a device for detecting electrical potential from said bearing to said ground comprising a voltage sensing means connected across said shaft and said bearing, said voltage sensing means indicating an increase in voltage when there is a condition exposing the unit to an increase in current flow from said bearing to said ground.
Claim 2
Dependent Claim
111 words
In combination with a dynamoelectric machine having an electrically grounded rotating shaft with electrical potential generated therein, a bearing rotatably supporting said shaft on a film of oil, said oil providing electrical insulation between said shaft and said bearing sufficient to cause a voltage potential across said oil film and electrical insulation isolating said bearing from electrical ground, a device for detecting electrical potential from said bearing to said ground comprising a voltage sensing means connected across said shaft and said bearing, said voltage sensing means indicating an increase in voltage when there is a condition exposing the unit to an increase in current flow from said bearing to said ground.
Claim 3
Dependent Claim
26 words
The combination set forth in claim 1 wherein said voltage sensing means indicates a decrease in voltage when there is a short across the oil film.
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) | 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 |