EP0054407B1 - Circuit de protection d'un courant de charge - Google Patents

Circuit de protection d'un courant de charge Download PDF

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Publication number
EP0054407B1
EP0054407B1 EP19810305812 EP81305812A EP0054407B1 EP 0054407 B1 EP0054407 B1 EP 0054407B1 EP 19810305812 EP19810305812 EP 19810305812 EP 81305812 A EP81305812 A EP 81305812A EP 0054407 B1 EP0054407 B1 EP 0054407B1
Authority
EP
European Patent Office
Prior art keywords
load current
switch
protection circuit
load
cut
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19810305812
Other languages
German (de)
English (en)
Other versions
EP0054407A1 (fr
Inventor
Stuart Charles Clatworthy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RESTBURY Ltd
Original Assignee
RESTBURY Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by RESTBURY Ltd filed Critical RESTBURY Ltd
Publication of EP0054407A1 publication Critical patent/EP0054407A1/fr
Application granted granted Critical
Publication of EP0054407B1 publication Critical patent/EP0054407B1/fr
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/20—Calibration, including self-calibrating arrangements
    • G08B29/22—Provisions facilitating manual calibration, e.g. input or output provisions for testing; Holding of intermittent values to permit measurement
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/12—Checking intermittently signalling or alarm systems
    • G08B29/14—Checking intermittently signalling or alarm systems checking the detection circuits
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H47/00—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
    • H01H47/002—Monitoring or fail-safe circuits

Definitions

  • the present invention relates to circuits to protect against failure of switches. Such circuits may also be used for testing switches without disturbing the system controlled by the switch.
  • a switch condition indicator circuit for indicating the open or closed condition of a load current switch.
  • the circuit includes an indicating lamp and a current control device for controlling the supply of current to the lamp.
  • the current control device is biased by a biasing circuit connected in parallel with the switch and the arrangement is such that the current control device is biased into a conducting condition to cause illumination of the indicating lamp when the switch is open and into a non-conducting condition causing the lamp to become extinguished when the switch is closed.
  • An alternative arrangement permits the indicating lamp to light when the external switch is closed rather than open.
  • a supply circuit for supplying current to a load comprising a load current cut-off switch which is connected in series with the load and which is responsive to a control output to switch from a normally conducting condition in which it conducts load current to the load to a non-conducting condition in which it cuts off load current to the load, characterised by the provision of a load current protection circuit having a load current path in parallel with the cut-off switch for maintaining the supply of load current to the load in the event that the cut-off switch fails to its non-conducting condition, the protection circuit comprising an auxiliary switch connected in the load current path of the protection circuit and so controlled by the control output as to be in a conducting condition permitting load current to flow in the load current path of the protection circuit when the cut-off switch is required to be in a conducting condition and to be in a non-conducting condition when the cut-off switch is required to be in a non-conducting condition, a switching diode so connected in the load current path of the protection circuit that with
  • the protection circuit includes voltage drop means in the load current path of the protection circuit, and the switching diode is connected in series with the voltage drop means and is biased to its non-conducting condition by the voltage drop across the voltage drop means.
  • the protection circuit includes a biasing diode connected in the load current path of the protection circuit and the alarm circuit includes an alarm switching transistor which is turned on by the voltage across the biasing diode produced by load current flowing therethrough.
  • a light-emitting diode may be included in the alarm circuit to produce a visible warning of switch failure when the alarm switching transistor is turned on.
  • the auxiliary switch comprises an auxiliary switching transistor which is connected in the load current path of the protection circuit and which is controlled in response to the control output.
  • the switching diode is biased to its non-conducting condition by the voltage drop across the auxiliary switching transistor and the biasing diode when said auxiliary switching transistor is turned on and the cut-off switch is in the conducting condition.
  • Fig. 1 a basic supply circuit in accordance with the invention comprising a normally closed load current cut-off switch S and a load current protection circuit connected in parallel therewith between points A and B.
  • the protection circuit comprises, connected in sequence, a control transistor T2, connection point C, a diode D1, connection point D, and isolating diode D2.
  • Transistor T2 and diode D1 cause such a voltage drop as to produce a reduced potential at D in the circuit whereby current is prevented from flowing through isolating diode D2.
  • transistor T1 does not conduct.
  • the protection circuit can of course still be controlled by means of light-emitting diode LED2 and transistor T2, and therefore if it is necessary for the load current to be switched off, this can be easily accomplished.
  • a similar protection circuit for use with a similar cut-off switch connected in the return path from the load L can be provided by reversing the diodes and using negative equivalents of the transistors.
  • connection point D can be connected to an auxiliary supply bus ASB, from which connections can be taken to a number of isolating diodes, D2(a) and D2(b) for example, each of which isolating diodes is associated with a switch S(a), S(b) respectively.
  • a single protection device including all the components of the load current protection circuit apart from the isolating diode may be connected to a number of isolating diodes associated with a number of switches, each controlling a load.
  • Each load has two individual control outputs, one in its supply path, and one in its return path.
  • the common part of the supply path and the common part of the return path are each provided with a separate protection device connected respectively to the auxiliary supply bus ASB and the auxiliary return bus ARB.
  • each component of the protection device may be duplicated both in series and in parallel, as can be seen from the circuit diagram of Fig. 3.
  • the load current protection circuit can also be used to test whether or not the switches are working. In the case of a normally closed switch, the switch is opened and the alarm circuit will give an output when the current by-passes the switch to flow through the protection circuit.
  • a method of testing a normally open switch may be carried out using the circuit shown in Figure 4.
  • a load current protection circuit as described above but with the isolating diode replaced by a dummy load is connected in parallel with a normally open switch Sy and the load L, and the normally open switch Sx is tested by closing the switch Sx. If the switch Sx is working correctly this will cause current to flow through the modified protection circuit causing an alarm output to be generated. Obviously since the load L is still connected in series with an open switch Sy, such an operation will not cause the load L to be energised.
  • This method can be carried out to test switches on both positive and negative sides of the load.

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  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Keying Circuit Devices (AREA)
  • Testing Electric Properties And Detecting Electric Faults (AREA)

Claims (6)

1. Circuit d'alimentation destiné à fournir un courant à une charge (L), comportant un commutateur (S) de coupure de courant de charge qui est connecté en série avec la charge (L) et qui réagit à une sortie de commande en passant d'une condition normalement conductrice dans laquelle il conduit un courant de charge vers la charge (L), à une condition non conductrice, dans laquelle il coupe le courant de charge vers la charge (L), caractérisé en ce qu'il comporte un circuit de protection de courant de charge comprenant un circuit de courant de charge en parallèle avec le commutateur de coupure (S) pour maintenir la fourniture d'un courant de charge à la charge (L) dans le cas où le commutateur de coupure (S) devient défaillant dans sa condition non conductrice, le circuit de protection comportant un commutateur auxiliaire (T2) connecté dans le circuit de courant de charge du circuit de protection et commandé par la sortie de commande de manière à se trouver en condition conductrice, permettant au courant de charge de circuler dans le circuit de courant de charge du circuit de protection quand le commutateur de coupure (S) doit être à l'état conducteur, et se trouvant dans une condition non conductrice lorsque le commutateur de coupure (S) doit se trouver en condition non conductrice, une diode de commutation (D2) connectée dans le circuit de courant de charge du circuit de protection de manière qu'avec le commutateur auxiliaire (T2) à l'état conducteur, la diode de commutation (D2) soit polarisée pour couper le courant de charge dans le circuit de charge du circuit de protection quand le commutateur de coupure (S) conduit le courant de charge, et pour conduire un courant de charge par le circuit de courant de charge du circuit de protection quand le commutateur de coupure (S) est en dérangement pour conduire le courant de charge, et un circuit d'alarme (T1, R1 ) réagissant à la conduction du courant de charge par le circuit de courant de charge du circuit de protection en produisant un signal d'alarme indiquant un dérangement du commutateur.
2. Circuit selon la revendication 1, caractérisé en ce que le circuit de protection comporte un dispositif de chute de tension (T2, D1) dans le circuit de courant de charge du circuit de protection, et en ce que la diode de commutation (D2) est connectée en série avec le dispositif de chute de tension (T2, D1) et est polarisée à l'état non conducteur par la chute de tension aux bornes du dispositif de chute de tension (T2, D1 ).
3. Circuit selon la revendication 2, caractérisé en ce que le circuit de protection comporte une diode de polarisation (D1) connectée dans le circuit de courant de charge du circuit de protection et en ce que le circuit d'alarme comporte un transistor de commutation d'alarme (T1) qui est débloqué par la chute de tension aux bornes de la borne de polarisation (D1), produite par le courant de charge qui y circule.
4. Circuit selon la revendication 3, caractérisé en ce que le circuit d'alarme comporte une diode électroluminescente (LED1) qui produit une alarme visible de dérangement du commutateur quand le transistor de commutation d'alarme (T1 ) est débloqué.
5. Circuit selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le commutateur auxiliaire (T2) consiste en un transistor de commutation auxiliaire qui est connecté dans le circuit de courant de charge du circuit de protection et qui est commandé en réponse à la sortie de commande.
6. Circuit selon la revendication 5, dépendante de la revendication 3, caractérisé en ce que la diode de commutation (D2) est polarisée en condition non conductrice par la chute de tension aux bornes du transistor de commutation auxiliaire (T2) et de la diode de polarisation (D1 ) quand ledit transistor de commutation auxiliaire (T2) est débloqué et que le commutateur de coupure (S) est en condition conductrice.
EP19810305812 1980-12-09 1981-12-09 Circuit de protection d'un courant de charge Expired EP0054407B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8039358 1980-12-09
GB8039358A GB2089591B (en) 1980-12-09 1980-12-09 Switch protection device

Publications (2)

Publication Number Publication Date
EP0054407A1 EP0054407A1 (fr) 1982-06-23
EP0054407B1 true EP0054407B1 (fr) 1985-10-23

Family

ID=10517844

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810305812 Expired EP0054407B1 (fr) 1980-12-09 1981-12-09 Circuit de protection d'un courant de charge

Country Status (3)

Country Link
EP (1) EP0054407B1 (fr)
DE (1) DE3172734D1 (fr)
GB (1) GB2089591B (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2249840B (en) * 1990-11-13 1995-01-11 Alireza Ghazi Hessami Universal digital input channel
ES2253065B1 (es) * 2004-03-22 2007-07-16 Jose Luis Diaz Mejia Dispositivo y metodo de proteccion ampliada de lineas electricas.

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3179930A (en) * 1961-03-28 1965-04-20 Cutler Hammer Inc Circuit condition indicating systems
US3505664A (en) * 1967-07-07 1970-04-07 Hubbell Inc Harvey Switch condition indicator
US3626248A (en) * 1970-02-06 1971-12-07 Struthers Dunn Contact monitoring system
US4191946A (en) * 1977-10-20 1980-03-04 Gonzalez Raymond J Warning apparatus with a line integrity supervisory circuit

Also Published As

Publication number Publication date
GB2089591B (en) 1985-05-22
GB2089591A (en) 1982-06-23
DE3172734D1 (en) 1985-11-28
EP0054407A1 (fr) 1982-06-23

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