US3597518A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electric arc furnace control
Assignee: Robicon Corp
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Filing: 1970-02-27
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Granted: 1971-08-03
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Expires: 1990-02-27
Abstract
Abstract A control system for electric arc furnaces incorporating proportional plus integral control characteristics. The system, which is designed to maintain constant arc impedance, develops an output voltage proportional to input impedance error and then adds a second voltage which increases with time at a rate proportional to the impedance error magnitude. When the combined voltages for a furnace electrode exceed a preset level, the drive motor for that electrode is actuated to move the electrode upwardly or downwardly to maintain the desired arc impedance. In this way, the system will respond quickly to large impedance errors, is insensitive to short term impedance fluctuations, and at the same time has a very high sensitivity to continuing small errors.
Inventors
- 👤 Roland W Roberts
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 02:15
CPC Classifications
H; H05; H05B; H05B7/00; H05B7/02; H05B7/144; H05B7/148; H05B7/152; Y; Y02; Y02P; Y02P10/00; Y02P10/25
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
171 words
In combination with an electric arc furnace of the type in which at least one electrode is positioned adjacent a molten pool of metal and a potential gradient established between the two to form an arc; a system for controlling the position of said electrode with respect to said molten pool of metal so as to maintain a desired arc impedance, said system comprising means for generating an error signal which varies as a function of a deviation in arc impedance from said desired impedance, a proportional plus integrating controller, means for applying said error signal to the input of said controller, means for comparing the output of said controller with a reference potential, means for moving said electrode toward said molten pool when the magnitude of said output exceeds the magnitude of said reference potential and is of one polarity, and means for moving said electrode away from said molten pool when the magnitude of said output exceeds the magnitude of said reference potential and is of the other polarity.
Claim 2
Dependent Claim
171 words
In combination with an electric arc furnace of the type in which at least one electrode is positioned adjacent a molten pool of metal and a potential gradient established between the two to form an arc; a system for controlling the position of said electrode with respect to said molten pool of metal so as to maintain a desired arc impedance, said system comprising means for generating an error signal which varies as a function of a deviation in arc impedance from said desired impedance, a proportional plus integrating controller, means for applying said error signal to the input of said controller, means for comparing the output of said controller with a reference potential, means for moving said electrode toward said molten pool when the magnitude of said output exceeds the magnitude of said reference potential and is of one polarity, and means for moving said electrode away from said molten pool when the magnitude of said output exceeds the magnitude of said reference potential and is of the other polarity.
Claim 3
Dependent Claim
20 words
The system of claim 1 wherein the output of said controller is a step function followed by a ramp function.
Claim 4
Dependent Claim
56 words
The system of claim 1 wherein the means for generating said error signal comprises means for developing a firsT signal which varies as a function of arc voltage, means for developing a second signal which varies as a function of arc current, and means for comparing said first and second signals to develop said error signal.
Claim 5
Dependent Claim
59 words
The system of claim 3 wherein said first signal is proportional to arc voltage V and said second signal is proportional to KI where I represents arc current and K represents the desired arc impedance, said first and second signals being of opposite polarity, and said comparing means subtracts said first and second signals to derive said error signal.
Claim 6
Dependent Claim
36 words
The system of claim 4 wherein said first and second signals are produced by rectifying alternating current voltages derived from across said arc and from current transformers coupled to a conductor supplying current to said electrodes.
Claim 7
Dependent Claim
49 words
The system of claim 1 wherein the means for comparing the output of said controller with a reference potential includes an absolute value stage for converting signals at the output of said controller of two polarities to a signal of one polarity which is compared with said reference potential.
Claim 8
Dependent Claim
23 words
The system of claim 1 including a relay device actuable when the magnitude of the output of said controller exceeds said reference potential.
Claim 9
Dependent Claim
52 words
The system of claim 7 wherein said means for moving said electrode comprises a motor and a motor control circuit therefor, and including means operable when said relay device is actuated for connecting the output of said controller to said motor control circuit and for converting said controller to a proportional controller.
Claim 10
Dependent Claim
20 words
The system of claim 8 wherein said relay device remains actuated after initial actuation until said error signal is zero.
References Cited (Backward Citations)
US3379817A
Cited
US3414657A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-08-02 | 1975-02-01 | 1975-08-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-02 | 1979-02-01 | 1979-08-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-02 | 1983-02-01 | 1983-08-03 | $7700.00 | Window Closed / Lapsed |