CA1263468A - Circuit interrupter using arc commutation - Google Patents
Circuit interrupter using arc commutationInfo
- Publication number
- CA1263468A CA1263468A CA000501395A CA501395A CA1263468A CA 1263468 A CA1263468 A CA 1263468A CA 000501395 A CA000501395 A CA 000501395A CA 501395 A CA501395 A CA 501395A CA 1263468 A CA1263468 A CA 1263468A
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- CA
- Canada
- Prior art keywords
- contacts
- circuit
- capacitor
- voltage
- circuit interrupter
- 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.)
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Abstract
CIRCUIT INTERRUPTER USING
ARC COMMUTATION
Abstract of the Disclosure A solid state circuit interrupter connected in parallel across a pair of separable contacts diverts the circuit current away from the contacts upon separation to extinguish the arc formed between the contacts. A zener diode within the solid state switch turns on a triac when the contact arc voltage reaches a predetermined magnitude for transferring the current to a capacitor. When the capacitor voltage reaches the clamping voltage of a metal oxide varistor connected in parallel with the capacitor, the current then transfers to the metal oxide varistor and rapidly approaches zero.
ARC COMMUTATION
Abstract of the Disclosure A solid state circuit interrupter connected in parallel across a pair of separable contacts diverts the circuit current away from the contacts upon separation to extinguish the arc formed between the contacts. A zener diode within the solid state switch turns on a triac when the contact arc voltage reaches a predetermined magnitude for transferring the current to a capacitor. When the capacitor voltage reaches the clamping voltage of a metal oxide varistor connected in parallel with the capacitor, the current then transfers to the metal oxide varistor and rapidly approaches zero.
Description
CIRCUIT INTERRUPTER USING
ARC COMMUTATIGN
Background of the Invention Canadian Application Serial No. 478,410 filed April 4, 1985 entitled "Solid State Current Limitiny Circuit Interrupter" in the name of E. K.
Howell discloses "arcless" circuit interruption ~y transferring current away from separating contacts ~y means of a solid state switch. The solid state SWit includes a transistor that is turned on ~y Means of a satura~le core current transformer and turned off when the current transformer core reaches saturation.
British Patent Specifications 1,072,267 and 1,152,903 entitled ~Improvements In or Rélating To The Prevention or Reduction of Arcing at A.C. Switch Contacts~ both in tlle name of Leonard Knott are relevant to the subject matter of the instant invention for their disclosure of tile use of a voltage dependent resistor to switch a silicon controlled rectifier across a pair of separating contacts.
U.S. Patent 3,904,931 issued Septem~er 9, 1975 entitled ~Overvoltage Protective CircuitR in the name of Arthur Leidich discloses the use of a silicon controlled rectifier shuntillg a protected device wherein a zener diode is used to switch the rectifier 12~ ;8 UpOII the occurrence of an overvoltaye condition within the circuit.
U.s. Patent 3,887,849 issued June 3, 197 entitled "Protective Circuit" in the name of Harry Nagel discloses the use of a semiconductor switch in series between a circuit breaker and a load to delay the application of source voltage to the load for a time greater tharl the circuit breaker tripping time.
A zener diode is used to turn on the semiconductor switch.
The use of a solid state switch across circuit interrupting contacts with various circuit arrangements employed to transfer the current away from the contacts is known. Applicant is also aware of the use of a position activated switcn sucn as a single-pole dou~le-throw switch arrangement used in combination with a capacitor and resistor as an RC arc ~uencher whereby an auxilliary pair of contacts simultaneously diverts the current from the main contacts through the RC circuit to extinyuish the arc that forms between the main contacts. Applicant is unaware however, of the use of a com~ination of voltaye dependent elements as arranged herein, for transferring current through a first circuit element for a time to de-ionize the initial arc plasma and to cool the contact surfaces to a temperature below thermionic emission and then to a second circuit element for a sufficient time to dissipate the energy stored in tlle inductance of the current path and to cause the current to drop to a sufficiently low value to interrupt the current.
41~-631 Summary of the Inverltion The invention comprises a solid state circuit interrupter using arc commutation wherein a solid state switch and a voltage dependent resistor are connected in parallel across a pair of separa~le contacts. A zener diode is arranyed to turn on the solid state switch when the arc voltage across tne separated contacts reaches a predetermined voltage. A
capacitor connected across the voltage dependent resistor charges to the clampiny voltage of the voltage dependent resistor which then becomes conductive to transfer the current away from the solid state switch. The clamping voltage is selected to be higher than the systems voltage to thereby cause the current to approach a low value and interrupt tne circuit.
Brief Description of the Drawings Figure 1 is a diagrammatic represelltation of the circuit interrupter of the instant invention;
Figure 2 is a graphic representation of tne variation in voltage across the contacts within the circuit interrupter depicted in Figure 1 as a functio of time; and Figure 3 is a graphic representatiorl of the current through the circuit depicted in Figure 1 as a function of time.
Description of the Preferred EmDodiment Figure 1 contains a protected circuit 10 consisting of an ~C voltage source 9 supplying operating power to a load represented by the combination of the resistor ~S and the inductance LS through a switch 11 whicll connects a pair of power bus conductors 14, 15 through corresponding contacts 12, 13. To extinguish the arc when contacts 12, 13 are separated, a circuit interrupter 16 is ~:-4tj8 41~ 318-- 4 --conllected in parallel with the contacts. The interrupter comprises a thyristor such as an SCR or a triac Ql in series with a capacitor C1 connectiny across the contacts. A varistor or a bi-directional zener diode Zl is connected between the gate of the triac and power bus conductor 14 througil a resistor RG. The zener diode can be connected across the gate of the triac and the main terminal 20 opposite the gate rather thall to the power conductor, for some applications. With the contacts 12, 13 closed, no current flows to the gate of the triac and the triac remaills in its off condition and capacitor Cl is completely discharged by resistor ~D. When the contacts are opened, an arc occurs betweell tlle contacts and current flows through tlle zener dlode when the arc voltage reaches a first predetermined value SUCII as approximately 100 volts, to turn on the triac. The current is transferred from the arc to the capacitor allowing the contacts to cool and the capacitor to charge to a second predetermined voltaye, approximately 1000 volts, which is the clampiny voltage of the voltage dependent silicon carbi~ie or metal oxide varistor MOV. The MOV then becomes conductive and the current transfers through the MOV.
Since the clamping voltage is higher than the system voltage VO~ the current rapidly approaches zero thereby completing the interruption process.
When an SCR is used in place of the thyristor within the circuit of Figure 1, a bridye rectifier is required between tlle AC source an~ the SCR, such as described within the ~C circuit arranyement disclosed within the aforementioned Canadian Application SN. 47~,410. When a DC voltage source is employed in place of the AC voltage source 9, a thyristor can be used in place of the triac and .
the zener diode tllell turns the thyristor on when the zener voltage reaciles the first predetermined value.
A 4-layer diode, such as d two terminal Shockley diode, can be used in place of ~oth the zener diode S and the thyristor in such a DC application. The voltage across the diode itself is selected to turn on the diode. In AC applications, a bidirectional voltage dependent 4-layer diode replaces the zener diode as well as the thyristor since no yate is re~uired to turn on t}~e diode. One example of such a bidirectional voltage dependent diode is a "Sidac"
which is a trade name of the Unitrode Company. The switch voltage Vs is depicted at 17 in Fiyure 2 for the following time sequences. The contacts first becoMe separated at to whereill an arc voltage develops which reaches zener voltage V2 at time tl at which time the bidirectional zener dlode becolnes conductive causing the current to transfer from the arc to the capacitor Cl through t}le triac. ~t t2, the capacitor voltaye V3 exceeds the clampiny voltaye of the MUV transferring the current through the MOV. At time t3, the current throuyh the circuit is completely interrupted and the switch voltage equals the source voltage V~.
Figure 3 depicts the SySteln current 1~
which corresponds to the time increments depicted in Figure 2 for the switch voltage 17. It is noted tllat the current only slightly decreases over the time increment from to~ when the contacts first open, to t2 when the MOV first becomes conductive. The current then rapidly deceases throuyh the M~V until t3 at which time the current ceases to flow.
The capacitor Cl may be replaced by a positive temperature coefficient resistor sucn as described in Canadian Application S.N. 47~,407 filed 41~-631~
~, _ April 4, 1985 in the name of ~. K. ~owell. The positive temperature coefficient resistor is descri~ed as having a relatively low resistance value at low operating temperatures and a very hign resistance at hig}ler operating temperatures. For efficient operation in the circuit described within the instant invelltion, the ratio of the hot to cold resistance should be in the order of 1000 to 1.
ARC COMMUTATIGN
Background of the Invention Canadian Application Serial No. 478,410 filed April 4, 1985 entitled "Solid State Current Limitiny Circuit Interrupter" in the name of E. K.
Howell discloses "arcless" circuit interruption ~y transferring current away from separating contacts ~y means of a solid state switch. The solid state SWit includes a transistor that is turned on ~y Means of a satura~le core current transformer and turned off when the current transformer core reaches saturation.
British Patent Specifications 1,072,267 and 1,152,903 entitled ~Improvements In or Rélating To The Prevention or Reduction of Arcing at A.C. Switch Contacts~ both in tlle name of Leonard Knott are relevant to the subject matter of the instant invention for their disclosure of tile use of a voltage dependent resistor to switch a silicon controlled rectifier across a pair of separating contacts.
U.S. Patent 3,904,931 issued Septem~er 9, 1975 entitled ~Overvoltage Protective CircuitR in the name of Arthur Leidich discloses the use of a silicon controlled rectifier shuntillg a protected device wherein a zener diode is used to switch the rectifier 12~ ;8 UpOII the occurrence of an overvoltaye condition within the circuit.
U.s. Patent 3,887,849 issued June 3, 197 entitled "Protective Circuit" in the name of Harry Nagel discloses the use of a semiconductor switch in series between a circuit breaker and a load to delay the application of source voltage to the load for a time greater tharl the circuit breaker tripping time.
A zener diode is used to turn on the semiconductor switch.
The use of a solid state switch across circuit interrupting contacts with various circuit arrangements employed to transfer the current away from the contacts is known. Applicant is also aware of the use of a position activated switcn sucn as a single-pole dou~le-throw switch arrangement used in combination with a capacitor and resistor as an RC arc ~uencher whereby an auxilliary pair of contacts simultaneously diverts the current from the main contacts through the RC circuit to extinyuish the arc that forms between the main contacts. Applicant is unaware however, of the use of a com~ination of voltaye dependent elements as arranged herein, for transferring current through a first circuit element for a time to de-ionize the initial arc plasma and to cool the contact surfaces to a temperature below thermionic emission and then to a second circuit element for a sufficient time to dissipate the energy stored in tlle inductance of the current path and to cause the current to drop to a sufficiently low value to interrupt the current.
41~-631 Summary of the Inverltion The invention comprises a solid state circuit interrupter using arc commutation wherein a solid state switch and a voltage dependent resistor are connected in parallel across a pair of separa~le contacts. A zener diode is arranyed to turn on the solid state switch when the arc voltage across tne separated contacts reaches a predetermined voltage. A
capacitor connected across the voltage dependent resistor charges to the clampiny voltage of the voltage dependent resistor which then becomes conductive to transfer the current away from the solid state switch. The clamping voltage is selected to be higher than the systems voltage to thereby cause the current to approach a low value and interrupt tne circuit.
Brief Description of the Drawings Figure 1 is a diagrammatic represelltation of the circuit interrupter of the instant invention;
Figure 2 is a graphic representation of tne variation in voltage across the contacts within the circuit interrupter depicted in Figure 1 as a functio of time; and Figure 3 is a graphic representatiorl of the current through the circuit depicted in Figure 1 as a function of time.
Description of the Preferred EmDodiment Figure 1 contains a protected circuit 10 consisting of an ~C voltage source 9 supplying operating power to a load represented by the combination of the resistor ~S and the inductance LS through a switch 11 whicll connects a pair of power bus conductors 14, 15 through corresponding contacts 12, 13. To extinguish the arc when contacts 12, 13 are separated, a circuit interrupter 16 is ~:-4tj8 41~ 318-- 4 --conllected in parallel with the contacts. The interrupter comprises a thyristor such as an SCR or a triac Ql in series with a capacitor C1 connectiny across the contacts. A varistor or a bi-directional zener diode Zl is connected between the gate of the triac and power bus conductor 14 througil a resistor RG. The zener diode can be connected across the gate of the triac and the main terminal 20 opposite the gate rather thall to the power conductor, for some applications. With the contacts 12, 13 closed, no current flows to the gate of the triac and the triac remaills in its off condition and capacitor Cl is completely discharged by resistor ~D. When the contacts are opened, an arc occurs betweell tlle contacts and current flows through tlle zener dlode when the arc voltage reaches a first predetermined value SUCII as approximately 100 volts, to turn on the triac. The current is transferred from the arc to the capacitor allowing the contacts to cool and the capacitor to charge to a second predetermined voltaye, approximately 1000 volts, which is the clampiny voltage of the voltage dependent silicon carbi~ie or metal oxide varistor MOV. The MOV then becomes conductive and the current transfers through the MOV.
Since the clamping voltage is higher than the system voltage VO~ the current rapidly approaches zero thereby completing the interruption process.
When an SCR is used in place of the thyristor within the circuit of Figure 1, a bridye rectifier is required between tlle AC source an~ the SCR, such as described within the ~C circuit arranyement disclosed within the aforementioned Canadian Application SN. 47~,410. When a DC voltage source is employed in place of the AC voltage source 9, a thyristor can be used in place of the triac and .
the zener diode tllell turns the thyristor on when the zener voltage reaciles the first predetermined value.
A 4-layer diode, such as d two terminal Shockley diode, can be used in place of ~oth the zener diode S and the thyristor in such a DC application. The voltage across the diode itself is selected to turn on the diode. In AC applications, a bidirectional voltage dependent 4-layer diode replaces the zener diode as well as the thyristor since no yate is re~uired to turn on t}~e diode. One example of such a bidirectional voltage dependent diode is a "Sidac"
which is a trade name of the Unitrode Company. The switch voltage Vs is depicted at 17 in Fiyure 2 for the following time sequences. The contacts first becoMe separated at to whereill an arc voltage develops which reaches zener voltage V2 at time tl at which time the bidirectional zener dlode becolnes conductive causing the current to transfer from the arc to the capacitor Cl through t}le triac. ~t t2, the capacitor voltaye V3 exceeds the clampiny voltaye of the MUV transferring the current through the MOV. At time t3, the current throuyh the circuit is completely interrupted and the switch voltage equals the source voltage V~.
Figure 3 depicts the SySteln current 1~
which corresponds to the time increments depicted in Figure 2 for the switch voltage 17. It is noted tllat the current only slightly decreases over the time increment from to~ when the contacts first open, to t2 when the MOV first becomes conductive. The current then rapidly deceases throuyh the M~V until t3 at which time the current ceases to flow.
The capacitor Cl may be replaced by a positive temperature coefficient resistor sucn as described in Canadian Application S.N. 47~,407 filed 41~-631~
~, _ April 4, 1985 in the name of ~. K. ~owell. The positive temperature coefficient resistor is descri~ed as having a relatively low resistance value at low operating temperatures and a very hign resistance at hig}ler operating temperatures. For efficient operation in the circuit described within the instant invelltion, the ratio of the hot to cold resistance should be in the order of 1000 to 1.
Claims (6)
1. A circuit interrupter comprising:
(a) first and second separable contacts connected serially in a circuit comprising a source of electric potential and a load so as to permit the passage of alternating and direct current flow and for interrupting current flow through said circuit;
(b) a switchable semiconductor having first and second main terminals and a gate and having said first main terminal connected in series circuit with a capacitor, said second main terminal and said capacitor being coupled respectively to said first and second contacts so that the series combination of said switchable semiconductor and said capacitor is connected across said separable contacts for transferring the current away from said contacts upon said contacts being opened;
(c) a Zener diode connected in circuit with the second of said contacts and said gate for turning on said switchable semiconductor upon the occurrence of a first predetermined voltage across said contacts which is not in excess of one hundred volts, so as to limit the voltage of any arc occurring across said contacts to the value of said first predetermined voltage, and to thereupon briefly and substantially reduce the voltage across said contacts to quench any arc; and (d) a voltage dependent resistor which becomes conductive at a second predetermined voltage being connected in circuit across said contacts for transferring said current away from said capacitor upon the occurrence of a second predetermined voltage across said contacts, said first predetermined voltage being lower than said second predetermined voltage.
(a) first and second separable contacts connected serially in a circuit comprising a source of electric potential and a load so as to permit the passage of alternating and direct current flow and for interrupting current flow through said circuit;
(b) a switchable semiconductor having first and second main terminals and a gate and having said first main terminal connected in series circuit with a capacitor, said second main terminal and said capacitor being coupled respectively to said first and second contacts so that the series combination of said switchable semiconductor and said capacitor is connected across said separable contacts for transferring the current away from said contacts upon said contacts being opened;
(c) a Zener diode connected in circuit with the second of said contacts and said gate for turning on said switchable semiconductor upon the occurrence of a first predetermined voltage across said contacts which is not in excess of one hundred volts, so as to limit the voltage of any arc occurring across said contacts to the value of said first predetermined voltage, and to thereupon briefly and substantially reduce the voltage across said contacts to quench any arc; and (d) a voltage dependent resistor which becomes conductive at a second predetermined voltage being connected in circuit across said contacts for transferring said current away from said capacitor upon the occurrence of a second predetermined voltage across said contacts, said first predetermined voltage being lower than said second predetermined voltage.
2. The circuit interrupter of claim 1 wherein said switchable semiconductor comprises a thyristor.
3. The circuit interrupter of claim 2 wherein said thyristor comprises a silicon controlled rectifier or a triac.
4. The circuit interrupter of claim 1 wherein said switchable semiconductor comprises a triac having first and second main terminals and said gate and wherein said Zener diode is connected in circuit with said gate and said first main terminal of said triac.
5. The circuit interrupter of claim 1 further including a current limiting resistor in series with said Zener diode.
6. The circuit interrupter of claim 1 further including a resistor in parallel with said capacitor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000501395A CA1263468A (en) | 1986-02-07 | 1986-02-07 | Circuit interrupter using arc commutation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000501395A CA1263468A (en) | 1986-02-07 | 1986-02-07 | Circuit interrupter using arc commutation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1263468A true CA1263468A (en) | 1989-11-28 |
Family
ID=4132435
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000501395A Expired CA1263468A (en) | 1986-02-07 | 1986-02-07 | Circuit interrupter using arc commutation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1263468A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101728812A (en) * | 2008-10-30 | 2010-06-09 | 韩国电力公社 | Line commutation type fault current limiter |
-
1986
- 1986-02-07 CA CA000501395A patent/CA1263468A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101728812A (en) * | 2008-10-30 | 2010-06-09 | 韩国电力公社 | Line commutation type fault current limiter |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |