US3590323A
Expired / Lapsed
US
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Peak current limiting system
Assignee: PROCESS ELECTRONICS Corp
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Filing: 1970-01-22
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Granted: 1971-06-29
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Expires: 1990-01-22
Abstract
Abstract A very fast acting peak current limiting system for the protection of semiconductor controlled rectifiers or thyristors and associated circuit components against damaging overloads resulting from short circuits. In a rectifier power supply system the input current of which is controlled by semiconductor controlled rectifiers, peak current is sensed on each incoming power line and compared with a preset reference. In event the peak current exceeds the reference, an error signal is generated which actuates a trigger circuit connected to the gate lead of the semiconductor controlled rectifiers to phase back these rectifiers to the nonconductive mode. The rectifiers are then slowly returned to the current threshold. If the overload was caused by a transient condition, normal current will flow. If the overload was due to a persistent condition, the slow return of the semiconductor rectifiers to an overload condition will permit supplementary control systems having a slower time response to control the current into the rectifiers. Such supplementary control system may comprise subsystems to control overloads due to either internal faults within the power supply system or external faults.
Inventors
- 👤 Neville Mapham
- 👤 James H Galloway
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:15
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/10; H02H7/12; H02H7/125; H02H7/127
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
114 words
In a system protecting semiconductor controlled rectifiers against short circuit conditions in a rectifier electric power supply system having an alternating current input and a direct current output, the improvement comprising means to sense peak current on the incoming alternating current lines, an input circuit connected to said sensing means generating an error signal when said peak current exceeds a predetermined level, switching means responsive to said error signal rapidly switching said semiconductor controlled rectifiers to the nonconducting mode, control circuit means automatically restoring current flow through said rectifiers on a gradual basis and control means of relatively slow response controlling the flow of current with said system in accordance with a predetermined limit.
Claim 2
Dependent Claim
114 words
In a system protecting semiconductor controlled rectifiers against short circuit conditions in a rectifier electric power supply system having an alternating current input and a direct current output, the improvement comprising means to sense peak current on the incoming alternating current lines, an input circuit connected to said sensing means generating an error signal when said peak current exceeds a predetermined level, switching means responsive to said error signal rapidly switching said semiconductor controlled rectifiers to the nonconducting mode, control circuit means automatically restoring current flow through said rectifiers on a gradual basis and control means of relatively slow response controlling the flow of current with said system in accordance with a predetermined limit.
Claim 3
Dependent Claim
110 words
In a system for protecting semiconductor controlled rectifiers against short circuit conditions when employed to control the supply of alternating current into a rectifier power supply system, the improvement comprising means to sense peak current on the incoming alternating current lines, an input circuit connected to said sensing means generating an error signal when said peak current exceeds a predetermined level, switching means responsive to said error signal rapidly switching said semiconductor rectifiers to the nonconducting mode, self-recovering control circuit means automatically restoring current flow through said rectifiers on a gradual basis, and supplementary control means of relatively slower response controlling the flow of current within said power supply system.
Claim 4
Dependent Claim
110 words
In a system for protecting semiconductor controlled rectifiers against short circuit conditions when employed to control the supply of alternating current into a rectifier power supply system, the improvement comprising means to sense peak current on the incoming alternating current lines, an input circuit connected to said sensing means generating an error signal when said peak current exceeds a predetermined level, switching means responsive to said error signal rapidly switching said semiconductor rectifiers to the nonconducting mode, self-recovering control circuit means automatically restoring current flow through said rectifiers on a gradual basis, and supplementary control means of relatively slower response controlling the flow of current within said power supply system.
Claim 5
Dependent Claim
32 words
The improvement of claim 2 wherein said semiconductor rectifiers are phased back to the nonconductive state with a time not in excess of one-half of one cycle of the incoming alternating current.
Claim 6
Dependent Claim
30 words
The improvement of claim 3 in which said switching means would repeatedly cycle to control the current into said system in event said supplementary control system should fail to function.
Claim 7
Dependent Claim
188 words
In a system for controlling the flow of alternating electric current into a rectifier power supply system by means of a plurality of semiconductor controlled rectifiers protected against short circuit conditions by an overload protective subsystem, the improvement comprising means for sensing the peak current flowing in the alternating current feed lines, input circuit means connected to said sensing means producing a signal corresponding to said current, reference circuit means producing a signal corresponding to a preselected peak alternating current flow level, comparator circuit means for comparing said current signal against said reference signal and generating an output error signal when said current signal exceeds said reference signal, switching circuit means rapidly phasing back said semiconductor controlled rectifiers to their nonconductive mode in response to said error signal, an active phase controlling subsystem for automatically rephasing said semiconductor rectifiers to their conductive mode as a gradually increasing rate of current flow, and supplementary control means in said power supply system responsive to said gradually increasing current to control said alternating current flow if said restored current flow should exceed a threshold limit preset within said supplementary control means.
Claim 8
Dependent Claim
188 words
In a system for controlling the flow of alternating electric current into a rectifier power supply system by means of a plurality of semiconductor controlled rectifiers protected against short circuit conditions by an overload protective subsystem, the improvement comprising means for sensing the peak current flowing in the alternating current feed lines, input circuit means connected to said sensing means producing a signal corresponding to said current, reference circuit means producing a signal corresponding to a preselected peak alternating current flow level, comparator circuit means for comparing said current signal against said reference signal and generating an output error signal when said current signal exceeds said reference signal, switching circuit means rapidly phasing back said semiconductor controlled rectifiers to their nonconductive mode in response to said error signal, an active phase controlling subsystem for automatically rephasing said semiconductor rectifiers to their conductive mode as a gradually increasing rate of current flow, and supplementary control means in said power supply system responsive to said gradually increasing current to control said alternating current flow if said restored current flow should exceed a threshold limit preset within said supplementary control means.
Claim 9
Dependent Claim
39 words
The improvement of claiM 5 wherein said supplementary control means has a relatively slow response to excessive current conditions compared to said other circuit elements and cannot respond to overload conditions with equal rapidity to said faster control means.
Claim 10
Dependent Claim
30 words
The improvement of claim 6 wherein said semicontrolled rectifiers are rephased to the nonconductive state in a period of time not in excess of one-half cycle of said alternating current.
Claim 11
Dependent Claim
25 words
The improvement of claim 7 wherein said power supply system includes semiconductor rectifiers connected in the alternating current feed lines supplying said power supply system.
Claim 12
Dependent Claim
56 words
The improvement of claim 8 wherein said supplementary control system comprises two independent active subsystems, one of said subsystems being connected in said system to sense and control excessive current conditions caused by internal faults within said power supply system and the other being connected to sense and control excessive current conditions caused by external faults.
Claim 13
Dependent Claim
23 words
The improvement of claim 9 wherein the said gradually rephased current is increased to a level above normal but below damaging excessive current.
Claim 14
Dependent Claim
58 words
The improvement of claim 10 wherein said external fault sensing circuit will respond to a current level slightly in excess of normal caused by an external fault and automatically limit the current in the primary circuit of said transformer below an excessive current level and control normal rated current into said system, thereby overriding said rapid switching system.
Claim 15
Dependent Claim
21 words
The improvement of claim 11 wherein said external fault sensing system is connected in said supply system externally of said rectifiers.
Claim 16
Dependent Claim
57 words
The improvement of claim 12 wherein said internal fault control system comprises a plurality of electrically trippable circuit breakers, an actuating circuit connected to said circuit breakers to trip said circuit breakers in response to a command signal and circuit means to generate a command signal when excessive current conditions due to an internal fault is sensed.
Claim 17
Dependent Claim
35 words
The improvement of claim 13 in which said circuit means generating said command signal supplies said command signal after an interval of time comprising a preselected number of switching cycles of said switching circuit means.
Claim 18
Dependent Claim
133 words
In a system protecting the components of a solid state rectifier power supply against both internal and external faults in which current into said system is controlled by semiconductor controlled rectifiers controlled by a phase control system including overcurrent protection means, the improvement comprising a self-recovering peak limiting circuit overriding said phase control circuit to rapidly phase back said SCR''s to their nonconductive state and then automatically restoring said current flow at a relatively slow rate until a threshold is reached at which said overcurrent protection means will operate to limit the flow of current into an external fault to normal rate current and disconnect said power supply system from its input power source after a predetermined delay, but before excessive current damages the circuit components, in the case of an internal short.
Claim 19
Dependent Claim
133 words
In a system protecting the components of a solid state rectifier power supply against both internal and external faults in which current into said system is controlled by semiconductor controlled rectifiers controlled by a phase control system including overcurrent protection means, the improvement comprising a self-recovering peak limiting circuit overriding said phase control circuit to rapidly phase back said SCR''s to their nonconductive state and then automatically restoring said current flow at a relatively slow rate until a threshold is reached at which said overcurrent protection means will operate to limit the flow of current into an external fault to normal rate current and disconnect said power supply system from its input power source after a predetermined delay, but before excessive current damages the circuit components, in the case of an internal short.
Claim 20
Dependent Claim
78 words
The improvement of claim 15 wherein said circuit comprises an input section generating a signal reflecting current flow into said power supply system, a reference section generating a reference signal reflecting a predetermined maximum current level, a comparator section comparing said signals and generating an error signal when said input signal exceeds said reference signals, and output circuit means responsive to said error signal to limit current flow within said power supply system to a predetermined safe value.
Claim 21
Dependent Claim
102 words
In the method of controlling the flow of alternating current within a rectifier power supply system of a plurality of semiconductor controlled rectifiers protected against short circuit conditions by an overload protective system, the improvement comprising the steps of sensing the peak current on the incoming alternating cuRrent feed lines, generating an error signal when said current exceeds a predetermined value, rapidly phasing back said semiconductors to their nonconductive mode in response to said error signal, automatically gradually restoring current flow through said rectifiers, and controlling the flow of restored current through said system by supplementary control means of relatively slow response.
Claim 22
Dependent Claim
102 words
In the method of controlling the flow of alternating current within a rectifier power supply system of a plurality of semiconductor controlled rectifiers protected against short circuit conditions by an overload protective system, the improvement comprising the steps of sensing the peak current on the incoming alternating cuRrent feed lines, generating an error signal when said current exceeds a predetermined value, rapidly phasing back said semiconductors to their nonconductive mode in response to said error signal, automatically gradually restoring current flow through said rectifiers, and controlling the flow of restored current through said system by supplementary control means of relatively slow response.
Claim 23
Dependent Claim
32 words
The method of claim 17 wherein said semiconductor rectifiers are phased back to the nonconductive state within a time not in excess of one-half of one cycle of the incoming alternating current.
Claim 24
Dependent Claim
61 words
The method of claim 18 including the step of controlling said restored current flow by more than one active subsystems, one of which subsystems being connected in said system to sense and control excessive current conditions caused by external faults and another of said subsystems being connected in said system to sense and control excessive current conditions caused by external faults.
Claim 25
Dependent Claim
30 words
The method of claim 19 including the step of controlling said restored current when said restored current exceeds a normal current level but before it reaches an excessive damaging level.
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) | 1974-06-28 | 1974-12-28 | 1975-06-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-06-28 | 1978-12-28 | 1979-06-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-06-28 | 1982-12-28 | 1983-06-29 | $7700.00 | Window Closed / Lapsed |