US3921038A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Static surge-current limiter
Assignee: Westinghouse Electric Corp
•
Filing: 1974-02-19
•
Granted: 1975-11-18
•
Expires: 1994-02-19
Abstract
Abstract A solid state or static current limiter which provides a relatively low impedance electrical current conducting path between a source of power and a load or between two interconnected sources or networks during non-overload conditions. The main current carrying device comprises a thyristor or similar gated element which is shunted by an auxiliary circuit which includes a capacitive element, a controlled thyristor and an inductance element. The capacitive element is shunted by a current limiting circuit which cooperates with the capacitive element to limit current in the load once the main current carrying thyristor has been turned off and the current flowing therethrough has been commutated into the auxiliary circuit as when an overload or short circuit condition has been sensed in the load. The rate of turnoff of the main thyristor is limited primarily by the inductive element in the auxiliary circuit. The inductive element need not carry appreciable load current for an extended period of time as the main current limiting function for the circuit is provided by forward biasing a diode which is connected in series with a current limiting capacitor shortly after the main thyristor has been turned off.
Inventors
- 👤 Andress Kernick
- 👤 John Rosa
- 👤 David L Bowles
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 08:44
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/02
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
275 words
A current limiting device, comprising: A. terminals adapted to be connected in circuit relationship in an electrical system with a load and a source of voltage; B. main circuit means disposed between said terminals for conducting electrical current in said electrical system; C. commutating circuit means connected between said terminals generally in parallel circuit relationship with said main circuit means, said commutating circuit means comprising: 1. controllable switch means which is actuated to conduct at least a portion of said current in said electrical system when said current flowing in said electrical system attains a predetermined condition; 2. blocking anD current limiting means connected in circuit relationship with said controllable switch means for causing said main circuit means to cease to conduct after said controllable switch means has been actuated to thereby cause said commutating current means to conduct substantially all of said current in said electrical system and to limit said current; 3. supplemental capacitive current limiting means connected in circuit relationship with said blocking means and said controllable switch means for further limiting said electrical current in said system; 4. generally passive diode means connected in circuit relationship with said current limiting means said controllable switch means and said blocking means, said passive diode means being forward biased by said blocking means in response to a predetermined amount of said system current flowing in said blocking means after said blocking means has caused said main circuit to cease to conduct to thereby cause said supplemental current limiting means to conduct a significant portion of said current in said electrical system to thereby limit said current in said system to a predetermined maximum value.
Claim 2
Dependent Claim
275 words
A current limiting device, comprising: A. terminals adapted to be connected in circuit relationship in an electrical system with a load and a source of voltage; B. main circuit means disposed between said terminals for conducting electrical current in said electrical system; C. commutating circuit means connected between said terminals generally in parallel circuit relationship with said main circuit means, said commutating circuit means comprising: 1. controllable switch means which is actuated to conduct at least a portion of said current in said electrical system when said current flowing in said electrical system attains a predetermined condition; 2. blocking anD current limiting means connected in circuit relationship with said controllable switch means for causing said main circuit means to cease to conduct after said controllable switch means has been actuated to thereby cause said commutating current means to conduct substantially all of said current in said electrical system and to limit said current; 3. supplemental capacitive current limiting means connected in circuit relationship with said blocking means and said controllable switch means for further limiting said electrical current in said system; 4. generally passive diode means connected in circuit relationship with said current limiting means said controllable switch means and said blocking means, said passive diode means being forward biased by said blocking means in response to a predetermined amount of said system current flowing in said blocking means after said blocking means has caused said main circuit to cease to conduct to thereby cause said supplemental current limiting means to conduct a significant portion of said current in said electrical system to thereby limit said current in said system to a predetermined maximum value.
Claim 3
Dependent Claim
55 words
blocking anD current limiting means connected in circuit relationship with said controllable switch means for causing said main circuit means to cease to conduct after said controllable switch means has been actuated to thereby cause said commutating current means to conduct substantially all of said current in said electrical system and to limit said current;
Claim 4
Dependent Claim
55 words
blocking anD current limiting means connected in circuit relationship with said controllable switch means for causing said main circuit means to cease to conduct after said controllable switch means has been actuated to thereby cause said commutating current means to conduct substantially all of said current in said electrical system and to limit said current;
Claim 5
Dependent Claim
86 words
The combination as claimed in claim 1 wherein said current which flows in said commutating circuit means is to rise at no greater a rate than a predetermined value, a rate limiting means for said commutating circuit means, said rate limiting means being connected in circuit relationship with said controllable switch means, said blocking means and said current limiting means generally solely for the purpose of allowing said current which flows in said commutating circuit to rise at a rate no greater than said predetermined value.
Claim 6
Dependent Claim
17 words
The combination as claimed in claim 2 wherein said rate limiting means comprises an inductance choke coil.
Claim 7
Dependent Claim
27 words
supplemental capacitive current limiting means connected in circuit relationship with said blocking means and said controllable switch means for further limiting said electrical current in said system;
Claim 8
Dependent Claim
27 words
supplemental capacitive current limiting means connected in circuit relationship with said blocking means and said controllable switch means for further limiting said electrical current in said system;
Claim 9
Dependent Claim
93 words
generally passive diode means connected in circuit relationship with said current limiting means said controllable switch means and said blocking means, said passive diode means being forward biased by said blocking means in response to a predetermined amount of said system current flowing in said blocking means after said blocking means has caused said main circuit to cease to conduct to thereby cause said supplemental current limiting means to conduct a significant portion of said current in said electrical system to thereby limit said current in said system to a predetermined maximum value.
Claim 10
Dependent Claim
93 words
generally passive diode means connected in circuit relationship with said current limiting means said controllable switch means and said blocking means, said passive diode means being forward biased by said blocking means in response to a predetermined amount of said system current flowing in said blocking means after said blocking means has caused said main circuit to cease to conduct to thereby cause said supplemental current limiting means to conduct a significant portion of said current in said electrical system to thereby limit said current in said system to a predetermined maximum value.
Claim 11
Dependent Claim
16 words
The combination as claimed in claim 1 wherein said blocking means comprises a storage capacitance element.
Claim 12
Dependent Claim
79 words
The combination as claimed in claim 4 wherein said generally passive diode means comprises a source of charging electrical current connected in circuit relationship with a diode bridge for providing electrical charging current to charge said storage capacitive element through said supplemental current limiting means to a predetermined voltage value with a predetermined voltage polarity during a period of time when said controllable switch is not actuated to conduct said portion of said current flowing in said electrical system.
Claim 13
Dependent Claim
49 words
The combination as claimed in claim 1 wherein said supplemental capacitance current limiting means comprises a second capacitive element which is charged by said current flowing therethrough to thereby develop a voltage thereacross which is in polarity opposition to said current flowing therethrough and which thereby limits said current.
Claim 14
Dependent Claim
60 words
The combination as claimed in claim 1 including a supplemental protective device connected in circuit relationship with said terminals, said supplemental capacitive current limiting means comprising a resistive element which limits said current flowing in said supplemental current limiting means but nevertheless allows said current to be sustained within safe limits to thus allow said supplemental protective device to operate.
Claim 15
Dependent Claim
70 words
The combination as claimed in claim 1 wherein said commutating circuit is bidirectional, said current in said electrical system also being bidirectional, said main circuit means also being bidirectional for conducting alternate portions of said bidirectional electrical current in said electrical system, said bidirectional commutating circuit cooperating with said bidirectional main circuit means and said passive diode means to commutate and limit said alternate portions of said bidirectional electrical current.
Claim 16
Dependent Claim
15 words
The combination as claimed in claim 8 which said bidirectional electrical current comprises alternating current.
Claim 17
Dependent Claim
29 words
The combination as claimed in claim 1 wherein said supplemental capacitive current limiting means comprises a resIstive element which limits said current flowing in said supplemental current limiting means.
Claim 18
Dependent Claim
85 words
The combination as claimed in claim 1 wherein said supplemental capacitive current limiting means comprises a resistive element and a second capacitive element connected in circuit relationship, said second capacitive element being charged by a portion of said current flowing through said supplemental capacitive current limiting means to thereby develop a voltage thereacross which is in polarity opposition to said later portion of current and which therefore limits said current in said electrical system, said resistive element also limiting said current in said electrical system.
Claim 19
Dependent Claim
25 words
The combination as claimed in claim 11 wherein said circuit relationship of said resistive element and said second capacitive element comprises a series circuit relationship.
Claim 20
Dependent Claim
43 words
The combination as claimed in claim 1 wherein said controllable switch means comprises a thyristor which is turned off until reactuated at the gate terminal thereof when said current through the main terminals thereof is generally reduced to zero by current limiting action.
Claim 21
Dependent Claim
52 words
The combination as claimed in claim 1 wherein said controllable switch means is connected in series circuit relationship with said blocking means, said supplemental current limiting means is connected in series circuit relationship with said passive diode means, said latter series combination being connected in parallel circuit relationship with said blocking means.
References Cited (Backward Citations)
US3098949A
Cited
US3558982A
Cited
US3558983A
Cited
US3823343A
Cited
US3794885A
Cited
US3723816A
Cited
US3725742A
Cited
US3737759A
Cited
US3763418A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |