Patent US3849706A successfully refreshed from Google Patents.
US3849706A
Expired / Lapsed
US
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Logarithmic computing circuit
Assignee: ABB Inc USA
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Filing: 1973-10-04
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Granted: 1974-11-19
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Expires: 1993-10-04
Abstract
Abstract A circuit for raising a quantity represented by an input signal to a variable power employing a reference logarithmic signal to automatically bias the circuit as the value of the exponent is varied. An embodiment of the circuit utilizes an input signal proportional to the magnitude of overcurrent through an electric transmission line, with the exponential response thereto being applied across an integrating capacitor to yield a variable inverse time current relationship, providing a unique charging network for use with overcurrent protective apparatus.
Inventors
- 👤 R Johnson
- 👤 J Fruhwald
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 01:10
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/08; H02H3/093; G; G06; G06G; G06G7/00; G06G7/12; G06G7/24
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
215 words
A logarithmic computing circuit for generating a computed output signal representing the value of a quantity raised to a variable power comprising: means providing a primary current signal corresponding to the quantity to be raised to a variable power; means providing a reference current signal; a primary logarithmic function generator providing a primary log signal logarithmically related to said primary current signal; a reference logarithmic function generator providing a reference log signal logarithmically related to said reference current signal; means providing a differential signal responsive to the difference between said primary and reference log signals; gain control means having an adjustable gain factor related to the desired value of the variable power and providing a gain control signal responsive to said differential signal as modified by the value of said gain factor; summing means adding said reference log signal to the gain control signal of said gain control means; and an antilogarithmic function generator responsive to the output of said summing means to provide a computed output signal corresponding to the magnitude of the primary current signal raised to a variable power, said antilogrithmic function generator being automatically calibrated for the gain selected in said gain control by that portion of the output of said summing means which is responsive to said reference log signal.
Claim 2
Dependent Claim
215 words
A logarithmic computing circuit for generating a computed output signal representing the value of a quantity raised to a variable power comprising: means providing a primary current signal corresponding to the quantity to be raised to a variable power; means providing a reference current signal; a primary logarithmic function generator providing a primary log signal logarithmically related to said primary current signal; a reference logarithmic function generator providing a reference log signal logarithmically related to said reference current signal; means providing a differential signal responsive to the difference between said primary and reference log signals; gain control means having an adjustable gain factor related to the desired value of the variable power and providing a gain control signal responsive to said differential signal as modified by the value of said gain factor; summing means adding said reference log signal to the gain control signal of said gain control means; and an antilogarithmic function generator responsive to the output of said summing means to provide a computed output signal corresponding to the magnitude of the primary current signal raised to a variable power, said antilogrithmic function generator being automatically calibrated for the gain selected in said gain control by that portion of the output of said summing means which is responsive to said reference log signal.
Claim 3
Dependent Claim
88 words
The circuit of claim 1 wherein the means providing the differential signal, the gain control means and the summing means are provided by a differential variable gain amplifier including an operational amplifier having an inverting and non-inverting input and an output; a fixed gain circuit connected between said inverting input and said output responsive to said reference log signal, resistance means connected between said primary and reference log signals; and a resistance varying movable adjustment means connecting said resistance means to the non-inverting input of said operational amplifier.
Claim 4
Dependent Claim
36 words
The circuit of claim 1 wherein the reference logarithmic function generator has a temperature responsive characteristic similar to that of the primary logarithmic function generator and antilogarithmic function generator, automatically compensating the circuit for temperature change.
Claim 5
Dependent Claim
132 words
A protective-relaying combination with universal time delay response characteristics for monitoring and protecting an electrical system, comprising: means deriving a primary current signal responsive to a quantity of the electrical system to be monitored, means providing a reference current signal, logarithmic computing means responsive to said primary and reference current signals and providing a computed output signal related to the ratio of said primary and reference current signals raised to a variable power, a storage device, means coupling said storage device to be charged in accordance with said computed output signal, means responsive to said primary current signal preventing the charging of said storage device until said primary current signal reaches a predetermined magnitude, and translating means responsive to the voltage across said storage device to provide protection for the electrical system.
Claim 6
Dependent Claim
132 words
A protective-relaying combination with universal time delay response characteristics for monitoring and protecting an electrical system, comprising: means deriving a primary current signal responsive to a quantity of the electrical system to be monitored, means providing a reference current signal, logarithmic computing means responsive to said primary and reference current signals and providing a computed output signal related to the ratio of said primary and reference current signals raised to a variable power, a storage device, means coupling said storage device to be charged in accordance with said computed output signal, means responsive to said primary current signal preventing the charging of said storage device until said primary current signal reaches a predetermined magnitude, and translating means responsive to the voltage across said storage device to provide protection for the electrical system.
Claim 7
Dependent Claim
130 words
The protective-relaying combination of claim 4 wherein the logarithmic computing means providing the computed output signal includes: a primary logarithmic function generator providing a primary log signal logarithmiCally proportional to the primary current signal, a reference logarithmic function generator providing a reference log signal logarithmically proportional to the reference current signal, differential variable gain amplifier means having a variable gain factor related to the desired value of the variable power and providing a variable differential signal dependent upon the difference between the primary and reference log signals as modified by said gain factor, and an antilogarithmic function generator providing a computed output signal antilogarithmically related to said variable differential signal and corresponding to the ratio of the primary current signal to the reference current signal raised to a variable power.
Claim 8
Dependent Claim
49 words
The protective-relaying combination of claim 5 wherein the primary and reference logarithmic function generators each include an operational amplifier having a transistor in circuit with both the input and the output of the operational amplifier, with said transistors having similar temperature responsive characteristics, to automatically compensate for temperature variation.
Claim 9
Dependent Claim
43 words
The protective-relaying combination of claim 5 wherein the antilogarithmic function generator includes an operational amplifier having inputs and an output, and a transistor, said transistor being connected between the output of the differential variable gain amplifier and an input of said operational amplifier.
Claim 10
Dependent Claim
67 words
The protective-relaying combination of claim 5 wherein the differential variable gain amplifier includes an operational amplifier having inverting and non-inverting inputs and an output, a fixed gain circuit connected between said inverting input and said output responsive to the reference log signal, resistance means connected between the primary and reference log signals, and a resistance varying movable adjustment means connecting said resistance means to said non-inverting input.
Claim 11
Dependent Claim
60 words
The protective-relaying combination of claim 4 wherein the means preventing the charging of the storage device until the primary current signal reaches a predetermined magnitude includes voltage comparing means providing a signal indicating the condition when the reference direct current magnitude exceeds the primary direct current magnitude and a switching device responsive to this condition to shunt said storage 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) | 1977-11-18 | 1978-05-20 | 1978-11-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-18 | 1982-05-20 | 1982-11-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-18 | 1986-05-20 | 1986-11-19 | $7700.00 | Window Closed / Lapsed |