CA2060161A1 - Surge absorber - Google Patents
Surge absorberInfo
- Publication number
- CA2060161A1 CA2060161A1 CA002060161A CA2060161A CA2060161A1 CA 2060161 A1 CA2060161 A1 CA 2060161A1 CA 002060161 A CA002060161 A CA 002060161A CA 2060161 A CA2060161 A CA 2060161A CA 2060161 A1 CA2060161 A1 CA 2060161A1
- Authority
- CA
- Canada
- Prior art keywords
- surge
- absorbing element
- surge absorbing
- switch
- absorber
- 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.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
- H02H9/042—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage comprising means to limit the absorbed power or indicate damaged over-voltage protection device
Abstract
ABSTRACT OF THE DISCLOSURE
A surge absorber comprises a surge absorbing element used for protecting electronic devices from surge voltages and a thermal response switch for preventing the electronic device from catching fire. The surge absorber of the present invention comprises a surge absorbing element, means for connecting the surge absorbing element to the communication lines of the device and in parallel with the device, and thermally activated means connecting the communication lines and the surge absorbing element, which in response to a given, higher temperature, disconnects the surge absorbing element from the communication lines, and, in response to another, lower temperature, reconnects the surge absorbing element and the electronic device to the communication lines.
A surge absorber comprises a surge absorbing element used for protecting electronic devices from surge voltages and a thermal response switch for preventing the electronic device from catching fire. The surge absorber of the present invention comprises a surge absorbing element, means for connecting the surge absorbing element to the communication lines of the device and in parallel with the device, and thermally activated means connecting the communication lines and the surge absorbing element, which in response to a given, higher temperature, disconnects the surge absorbing element from the communication lines, and, in response to another, lower temperature, reconnects the surge absorbing element and the electronic device to the communication lines.
Description
This invention relates to a surge absorber suit~ble for protecting electronic devices used for communication equipment, such as, Eacsimiles, telephone switchboards, modems, and the like, from surge voltages and continuous overvoltages or overcurrents. ~ore particularly, it relates to a surge absorber which includes a surge absorbiny element used for protecting the electronic devices from surge voltages and a thermal response switch used for preventing abnormal and deleterious heating of the surge absorbing element when continuous overvoltages or overcurrents flow to the surge absorber.
In the prior art, a conventional surge absorbing element, e.g., a gas charge tube, is connected in parallel to an electronic device to be protected via a pair of input lines of the electronic device, and is designed to operate at a higher voltage than the operating voltage of the electronic device. Such a prior art surge absorbing element is a resistor having a high resistance when the voltage applied thereto is lower than the discharge voltage thereof and a resistance tens of ohms lower, when the voltage applied thereto is higher than the discharge starting voltage thereof. Accordingly, when surge voltages, such as, lighting surges, etc., are instantaneously applied to an electronic circuit including the surge absorbing element and the electronic device, the surge absorbing element discharges to suppress the surge voltages, and serves to protect the electronic device from the surge voltages.
However, when an overvoltage or overcurrent, e.g., due to a faulted condition, is continuously applied to the electronic circuit, a certain current continuously flows through the surge absorbing element. This results in the surge absorbing element being heated to high temperatures. The heat radiating from the surge absorbing element can cause the protected electronic device as well ~ j~s~ V~
as other electronic devices surrounding the surge absorbing element to catch fire.
A typical e~ample of a faulted situation would be the case when the input, i.e., signal or communication lines of the electronic device contact the power lines thereof. While it does not usually happen that such accidental overvoltages or overcurrents are continuously applied to the surge absorbing element, to achieve maximum safety, it has recently become desirable to take additional safety measures to avold such accidental problems and the potential fires caused therehy. As an example, UL
~Underwriter's Laboratories Inc.) of the U.S.A. prescribes a safety standard for surye absorbing elements 50 that they do not cause fire or electrical shocks in communication e~uipment surrounding the surge absorbing element when continuous overvoltages or overcurrents are applied.
PCT patent application No. JP 90/01006 discloses a surge absorber comprising a surge absorbing element used for suppressing the surge voltages and a metal wire connected in series to the surge absorbing elemen-t to prevent over-heating of the surge absorbing element.
It is an object of this invention to provide a surge absorber comprising a surge absorbing element for protecting electronic devices from surge voltages and a thermal response switch for preventing the electronic devices and other electronic devices surrounding the surge absorber from catching fire due to over-heating of the surge absorbing element from continuous overvoltages or overcurrents.
It is another object of this invention to provide a surge absorber comprising a surge absorbing element and a thermal response switch which automatically returns to its original position after the continuous overvoltages or overcurrents stop.
These objects are accomplished by the surge absorber of the present invention comprising a surge absorbing element, means for connecting the surge absorbing element to signal means of an e.lectronic device in parallel with said device, and thermally activated means electrically connecting the signal means and the surge absorbing element which, in response to a given second, higher temperature, disconnects the surge absorbing element from the signal means and, in response to another lower, first temperature, reconnects the surge absorbing element to the signal means.
Figure 1 illustrates a perspective vlew of a surge absorber in accordance w:ith this invention;
Figure 2 illustrates a front elevation view of the surge absorber shown in Figure 1 with a corner portion of an insulating plate broken away;
Figure 3 shows the circuit diagram of the surge absorber;
Figure 4 illustrates a front view of a prior art surge absorber; and Figure 5 shows the circuit diagram of the prior art surge absorber shown in E'igure 4.
A conventional surge absorber is shown in Figures 4 and 5 and described in the following.
In the surge absorber, a first lead 1~, a second lead 18 and a third lead 19, are attached to a base plate 16. One end of metal wire 15 having spring elasticity is welded to an end of the first lead 17. A surge absorbing element 14 is connected between the second lead 18 and the third lead 19 through lead wires 14a and 14b. The metal wire 15 is attached, as by a weld, to one end of the first lead 1~, and is bent in a spring-loaded position in the direction of the surge absorbing element 14. Th~ other end of the bent spring-loaded wire 15 is attached by solder 28 to one end of lead wire 14a, which is connected to the second lead 18. The metal wire 15 and the surge absorbing element 14 are encased within casing 24, which is attached to baseplate 16.
~ s shown in Figure 5, the ~irst le~d 17 is connected to an input line lla of an electronic device 10, the second lead 18 is cvnnected to an input line llb of electronic device 10, and the third leacl 19 is connected to line 12 which is connected to electronic device 10. The metal wire 15 does not disconnect when a surge voltage is instantaneously applied to the above surge absorber, but it disconnects to preven~ a current flowing to fhe surge absorbing element 14 when subjected to large current at an overvoltage.
In particular, when a small current at an overvoltage flows, solder 28 is melted by the heat generated by both the current and the surge absorbing element 1~, and wire 15 releases from its spring-loaded position and disconnects from its attachment to lead wire 14a thereby preventing the current from flowing to the surge absorbing element 14. Howaver, if the surge voltages are repeatedly applied to the surge absorber, wire 15 loses its spring elasticity because it is repeatedly annealed by the heat of the surges. As a result, it may not spring back and detach from lead wire 14a.
Consequently, the small current at the overvoltage continues to flow into the surge absorbing element, the surge absorbing element i5 over-heated by the current and causes the electronic device as well as other electronic devices surrounding the surge absorber to catch ~ire. For the above reasons, this surge absorber cannot pass the U.L. safety standard.
The surge absorber according to this invention comprises a surge absorbing element series connected to a thermal response switch having an automatic restoration function, i.e., an on-off switch. The thermal response switch comprises a fixed contacting point piece and a contacting point attache~ to a bimetallic or memorizing alloy element.
When a surge voltage is instantaneously applied to this device, the thermal response switch remains in the closed or on position and the surge absorbing ele~ent acts ~to suppress the surge voltage. When an overvoltage or :5 overcurrent is continuously applied to the surge absorber o~ the present invention, the thermal response switch opens to the off position due to t:he heat generated by the continuous flow of current through the line, the heat radiated from the surge absorbing element or both.
Accordingly, when a continuous overvoltage or overcurrent flows to the communication lines, the thermal response switch generates heat because it itself is a resistor, and the surge absorbing element is also simultaneously heated by the current flowing thereto. When the temperature of the thermal response switch attains a predetermine~ temperature due to the heat which it generates or the heat radiating ~rom the surge absorbing element, the contact point provided on a bimetallic piece of the switch moves away from a contact piec~ due to the characteristics of the bimetallic element or alloy, thus stopping the continuous overvoltage or overcurrent from flowing to the surge absorbing element.
When the continuous overvoltage or overcurrent flowing to the communication or signal lines ceases and the temperature of the thermal response switch decreases to the predetermined temperature or less, the thermal response contacting point again moves into contact with the fixed contacting point piece to restore the electronic circuit.
The surge absorbing element used for this inven~ion may be a semi-conductor t~pe surge absorber, such as, a zinc o~ide varistor, a carbon silicate varistor or a 2ener diode, a filter type surge absorber, such as, a CL
filter made by combining a condenser with a coil or a CR
~ilter made by combining a condenser with a resistor, or a gap type discharge tube, such as, an air gap type absorber or micro-gap type absorber.
The therma,l response switch used ~or this invention is an on-off switch and usually has an opera-tion starting temperature range of 80 to 120~ because the electronic devices used together with the surge absorbers normally have a maximuJn operating temperature of 85C.
Bimetallic elements suitable for use in the thermal response switch of the invention include those comprising a joined body of two metal pieces wherein one metal piece has a different thermal expansion coeffici0nt from that of the other metal piece, e.g. a brass-nickel steel joined body having a thermal modification starting temperature range of 80 to 100 C, a manganese-Invar* joined body having a thermal modification starting temperature range of 100 to 150 C or a brass-Invar* ~oined body having a thermal modification starting temperature range of 100to 150C.
Memorizing alloys suitable for use in the thermal response swi-tch include nickel-titanium alloy which can adjust the modification point up to 90C or a copper-zinc-aluminum alloy which can adjust the modification point upto 100 C. It is desirable to arrange the thermal response switch near the surge absorbing element because the thermal response switch is rapidly opened by the combination o~ the heat radiated from the surge absorbing element and the heat generated by the switch when a continuous overvoltage or overcurrent flows to the surge absorbér. It is further desirable to encase the thermal response switch arranged near the surge absorbing element and the surge absorbing element in a housing because the thermal response switch can be more rapidly activated due to its own heat, thus decreasing the heating of the other elements.
In this specification, the term "an overvoltage or overcurrent" means an abnormal voltage above a discharge starting voltage of a surge absorbing element or an abnormal current accompanied by the abnormal voltage.
` '3~
Referring to Figure 1, a perspective view of the surge absorber of the presen~ invention is shown. A front view of the surge absorber is shown in Figure 2. Three spaced~apart pin type leads 1~, 18 and 19 are attached to an insulator base plate 16 and penetrate through the base plate 16 so that the ends of the leads or pins are accessible to the exterior of the housing 24 encasing the device. The housing 24 is shown in phantom for clarity in Figure 2. As depicted, one wall or portio~ of housing 24 o is formed from by base plate 1~, which is made from an insulating material. Leads 1~, 18 and 19 penetrate through plate 16 so that the ends or pins are electrically accessible from exterior of the housing. The leads used in this embodiment are a nickel alloy. A thermal response switch 21 i9 connected between lead 17 and lead 18. A
surge absorbing element 14 is connected between lead 18 and lead 19 through lead wires 14a and 14b.
For this example, the surge absorbing element 14 is a micro-gap type discharge tube having a discharge starting voltage of 300 volts. This surge absorbing element 14 is manufactured by coating a columnar ceramic element with a conductive thin film, forming micro-gaps which are perpendicular to the ceramic element on a surface of the coated ceramic element, attaching cap electrodes to both ends of the coated ceramic element, connecting lead wires to the cap electrodes and then enclosing the resulting product with an inert gas in a glass tube.
For this example, the thermal response switch 21 comprises a fixed contact piece 22 and a bimetallic piece 23 having contact point 23a attached thereto. One end of the fixed contact piece 22 is welded to the lead 1~ and one end of the bimetallic piece 23 is welded to the lead 18.
Fixed contacting piece 22 usually contacts point 23. The bimetallic piece 23 is a joined body of a manganese piece and an Invar* piece. However, a shape memorizing alloy piece may be used in place of bimetallic piece 23.
In this embodiment, contact point 23a soldered to the bimetallic piece 23 contacts fl~ed contact piece 22 when the temperature of the bimetallic piece 23 is below 100 C. When the temperature thereof goes above lOO~C due to the heat generated by bimetallic piece 23, and/or surge absorbing element 1~, it moves away from fixed contact piece 22 due to the thermal modification of bimetallic piece 23, i.e., piece 23 is bent in the direction o~ the surge absorbing element 14 b~ the thermal modification thereo~ due to the respective differential thermal expansions of the component met:als. This stops the current flow to the surge absorbing element and the electronic device.
When the temperature of piece 23 decreases to below 100C by removal of the overvoltage or overcurrent, contact point 23a regains its position contact fixed contacting point piece 22. Preferably, switch 21 is positioned near the surge absorbing element 14 within housing 24. Figure 3 depicts a circuit diagram of the 20 embodiment of Figures 1 and 2. Leads 17, 13 and 19 are connected to the lines lla, llb and 12, respectively.
Numeral 13 designates the surge absorber.
The following tests illustrate the invention:
Test 1 A relatively large electric current at an overvoltage, i.e., an electric current of 40 A at 600 volts AC, is applied for 1.5 sec to communication or signal lines lla and 12 of the circuit shown in Figure 3. After a short time of 4 milliseconds from the start of the passing the current, heat is generated in bimetallic piece 23, and/or the surge protecting element, which radiates to piece 23.
As a result, bimetallic piece moves toward the surge absorber and point 23a moves away of contact with piece 22.
~ontact point 23a remains out of contact with piece 22 so long as the overvoltage is applied. When the overvol-tage is stopped, contactiny point 23a moves bac~ to contact fixed contact piece 22.
est 2 ~ relatively small electrîc curr0nt of an overvoltage, i.e., an electric current of 2.2 A at 600 volts AC, is applied to communic:ation lines lla and 12 of the circuit shown in F.igure 3 for 30 minutes. Cantacting point 23a moves repeatedly between the on (contact) and off (out-of-contact) positions due to the repeated actuation operations o~ bimetallic piece 23 caused by the heating or cooling of this element during the application of the overvoltage. The on (contact) period averages several milliseconds and the off (out-of-contact) period averages of 2 to 5 seconds.
In Tests 1 and 2, thermal damage or fire do not occur in the surge absorber and the electronic device used for the tests. Accordingly, since this surge absorber rapidly responds to -the continuous overvoltages or overcurrents and then disconnects the electronic circuit due to the thermal modification of the thermal response switch, thermal damage of the electronic devices caused by abnormal heating of the surge absorbing element due to the continuous overvoltages or overcurrents is avoided.
Furthermore, since the the.rmal response switch has a self-restoration function, this surge absorber can maintain itssurge suppression function and withstand continuous overvoltages or overcurrents without having to replace the thermal response switch. This results in a higher reliability and efficiency than observed with the conventional surge absorber.
;
In the prior art, a conventional surge absorbing element, e.g., a gas charge tube, is connected in parallel to an electronic device to be protected via a pair of input lines of the electronic device, and is designed to operate at a higher voltage than the operating voltage of the electronic device. Such a prior art surge absorbing element is a resistor having a high resistance when the voltage applied thereto is lower than the discharge voltage thereof and a resistance tens of ohms lower, when the voltage applied thereto is higher than the discharge starting voltage thereof. Accordingly, when surge voltages, such as, lighting surges, etc., are instantaneously applied to an electronic circuit including the surge absorbing element and the electronic device, the surge absorbing element discharges to suppress the surge voltages, and serves to protect the electronic device from the surge voltages.
However, when an overvoltage or overcurrent, e.g., due to a faulted condition, is continuously applied to the electronic circuit, a certain current continuously flows through the surge absorbing element. This results in the surge absorbing element being heated to high temperatures. The heat radiating from the surge absorbing element can cause the protected electronic device as well ~ j~s~ V~
as other electronic devices surrounding the surge absorbing element to catch fire.
A typical e~ample of a faulted situation would be the case when the input, i.e., signal or communication lines of the electronic device contact the power lines thereof. While it does not usually happen that such accidental overvoltages or overcurrents are continuously applied to the surge absorbing element, to achieve maximum safety, it has recently become desirable to take additional safety measures to avold such accidental problems and the potential fires caused therehy. As an example, UL
~Underwriter's Laboratories Inc.) of the U.S.A. prescribes a safety standard for surye absorbing elements 50 that they do not cause fire or electrical shocks in communication e~uipment surrounding the surge absorbing element when continuous overvoltages or overcurrents are applied.
PCT patent application No. JP 90/01006 discloses a surge absorber comprising a surge absorbing element used for suppressing the surge voltages and a metal wire connected in series to the surge absorbing elemen-t to prevent over-heating of the surge absorbing element.
It is an object of this invention to provide a surge absorber comprising a surge absorbing element for protecting electronic devices from surge voltages and a thermal response switch for preventing the electronic devices and other electronic devices surrounding the surge absorber from catching fire due to over-heating of the surge absorbing element from continuous overvoltages or overcurrents.
It is another object of this invention to provide a surge absorber comprising a surge absorbing element and a thermal response switch which automatically returns to its original position after the continuous overvoltages or overcurrents stop.
These objects are accomplished by the surge absorber of the present invention comprising a surge absorbing element, means for connecting the surge absorbing element to signal means of an e.lectronic device in parallel with said device, and thermally activated means electrically connecting the signal means and the surge absorbing element which, in response to a given second, higher temperature, disconnects the surge absorbing element from the signal means and, in response to another lower, first temperature, reconnects the surge absorbing element to the signal means.
Figure 1 illustrates a perspective vlew of a surge absorber in accordance w:ith this invention;
Figure 2 illustrates a front elevation view of the surge absorber shown in Figure 1 with a corner portion of an insulating plate broken away;
Figure 3 shows the circuit diagram of the surge absorber;
Figure 4 illustrates a front view of a prior art surge absorber; and Figure 5 shows the circuit diagram of the prior art surge absorber shown in E'igure 4.
A conventional surge absorber is shown in Figures 4 and 5 and described in the following.
In the surge absorber, a first lead 1~, a second lead 18 and a third lead 19, are attached to a base plate 16. One end of metal wire 15 having spring elasticity is welded to an end of the first lead 17. A surge absorbing element 14 is connected between the second lead 18 and the third lead 19 through lead wires 14a and 14b. The metal wire 15 is attached, as by a weld, to one end of the first lead 1~, and is bent in a spring-loaded position in the direction of the surge absorbing element 14. Th~ other end of the bent spring-loaded wire 15 is attached by solder 28 to one end of lead wire 14a, which is connected to the second lead 18. The metal wire 15 and the surge absorbing element 14 are encased within casing 24, which is attached to baseplate 16.
~ s shown in Figure 5, the ~irst le~d 17 is connected to an input line lla of an electronic device 10, the second lead 18 is cvnnected to an input line llb of electronic device 10, and the third leacl 19 is connected to line 12 which is connected to electronic device 10. The metal wire 15 does not disconnect when a surge voltage is instantaneously applied to the above surge absorber, but it disconnects to preven~ a current flowing to fhe surge absorbing element 14 when subjected to large current at an overvoltage.
In particular, when a small current at an overvoltage flows, solder 28 is melted by the heat generated by both the current and the surge absorbing element 1~, and wire 15 releases from its spring-loaded position and disconnects from its attachment to lead wire 14a thereby preventing the current from flowing to the surge absorbing element 14. Howaver, if the surge voltages are repeatedly applied to the surge absorber, wire 15 loses its spring elasticity because it is repeatedly annealed by the heat of the surges. As a result, it may not spring back and detach from lead wire 14a.
Consequently, the small current at the overvoltage continues to flow into the surge absorbing element, the surge absorbing element i5 over-heated by the current and causes the electronic device as well as other electronic devices surrounding the surge absorber to catch ~ire. For the above reasons, this surge absorber cannot pass the U.L. safety standard.
The surge absorber according to this invention comprises a surge absorbing element series connected to a thermal response switch having an automatic restoration function, i.e., an on-off switch. The thermal response switch comprises a fixed contacting point piece and a contacting point attache~ to a bimetallic or memorizing alloy element.
When a surge voltage is instantaneously applied to this device, the thermal response switch remains in the closed or on position and the surge absorbing ele~ent acts ~to suppress the surge voltage. When an overvoltage or :5 overcurrent is continuously applied to the surge absorber o~ the present invention, the thermal response switch opens to the off position due to t:he heat generated by the continuous flow of current through the line, the heat radiated from the surge absorbing element or both.
Accordingly, when a continuous overvoltage or overcurrent flows to the communication lines, the thermal response switch generates heat because it itself is a resistor, and the surge absorbing element is also simultaneously heated by the current flowing thereto. When the temperature of the thermal response switch attains a predetermine~ temperature due to the heat which it generates or the heat radiating ~rom the surge absorbing element, the contact point provided on a bimetallic piece of the switch moves away from a contact piec~ due to the characteristics of the bimetallic element or alloy, thus stopping the continuous overvoltage or overcurrent from flowing to the surge absorbing element.
When the continuous overvoltage or overcurrent flowing to the communication or signal lines ceases and the temperature of the thermal response switch decreases to the predetermined temperature or less, the thermal response contacting point again moves into contact with the fixed contacting point piece to restore the electronic circuit.
The surge absorbing element used for this inven~ion may be a semi-conductor t~pe surge absorber, such as, a zinc o~ide varistor, a carbon silicate varistor or a 2ener diode, a filter type surge absorber, such as, a CL
filter made by combining a condenser with a coil or a CR
~ilter made by combining a condenser with a resistor, or a gap type discharge tube, such as, an air gap type absorber or micro-gap type absorber.
The therma,l response switch used ~or this invention is an on-off switch and usually has an opera-tion starting temperature range of 80 to 120~ because the electronic devices used together with the surge absorbers normally have a maximuJn operating temperature of 85C.
Bimetallic elements suitable for use in the thermal response switch of the invention include those comprising a joined body of two metal pieces wherein one metal piece has a different thermal expansion coeffici0nt from that of the other metal piece, e.g. a brass-nickel steel joined body having a thermal modification starting temperature range of 80 to 100 C, a manganese-Invar* joined body having a thermal modification starting temperature range of 100 to 150 C or a brass-Invar* ~oined body having a thermal modification starting temperature range of 100to 150C.
Memorizing alloys suitable for use in the thermal response swi-tch include nickel-titanium alloy which can adjust the modification point up to 90C or a copper-zinc-aluminum alloy which can adjust the modification point upto 100 C. It is desirable to arrange the thermal response switch near the surge absorbing element because the thermal response switch is rapidly opened by the combination o~ the heat radiated from the surge absorbing element and the heat generated by the switch when a continuous overvoltage or overcurrent flows to the surge absorbér. It is further desirable to encase the thermal response switch arranged near the surge absorbing element and the surge absorbing element in a housing because the thermal response switch can be more rapidly activated due to its own heat, thus decreasing the heating of the other elements.
In this specification, the term "an overvoltage or overcurrent" means an abnormal voltage above a discharge starting voltage of a surge absorbing element or an abnormal current accompanied by the abnormal voltage.
` '3~
Referring to Figure 1, a perspective view of the surge absorber of the presen~ invention is shown. A front view of the surge absorber is shown in Figure 2. Three spaced~apart pin type leads 1~, 18 and 19 are attached to an insulator base plate 16 and penetrate through the base plate 16 so that the ends of the leads or pins are accessible to the exterior of the housing 24 encasing the device. The housing 24 is shown in phantom for clarity in Figure 2. As depicted, one wall or portio~ of housing 24 o is formed from by base plate 1~, which is made from an insulating material. Leads 1~, 18 and 19 penetrate through plate 16 so that the ends or pins are electrically accessible from exterior of the housing. The leads used in this embodiment are a nickel alloy. A thermal response switch 21 i9 connected between lead 17 and lead 18. A
surge absorbing element 14 is connected between lead 18 and lead 19 through lead wires 14a and 14b.
For this example, the surge absorbing element 14 is a micro-gap type discharge tube having a discharge starting voltage of 300 volts. This surge absorbing element 14 is manufactured by coating a columnar ceramic element with a conductive thin film, forming micro-gaps which are perpendicular to the ceramic element on a surface of the coated ceramic element, attaching cap electrodes to both ends of the coated ceramic element, connecting lead wires to the cap electrodes and then enclosing the resulting product with an inert gas in a glass tube.
For this example, the thermal response switch 21 comprises a fixed contact piece 22 and a bimetallic piece 23 having contact point 23a attached thereto. One end of the fixed contact piece 22 is welded to the lead 1~ and one end of the bimetallic piece 23 is welded to the lead 18.
Fixed contacting piece 22 usually contacts point 23. The bimetallic piece 23 is a joined body of a manganese piece and an Invar* piece. However, a shape memorizing alloy piece may be used in place of bimetallic piece 23.
In this embodiment, contact point 23a soldered to the bimetallic piece 23 contacts fl~ed contact piece 22 when the temperature of the bimetallic piece 23 is below 100 C. When the temperature thereof goes above lOO~C due to the heat generated by bimetallic piece 23, and/or surge absorbing element 1~, it moves away from fixed contact piece 22 due to the thermal modification of bimetallic piece 23, i.e., piece 23 is bent in the direction o~ the surge absorbing element 14 b~ the thermal modification thereo~ due to the respective differential thermal expansions of the component met:als. This stops the current flow to the surge absorbing element and the electronic device.
When the temperature of piece 23 decreases to below 100C by removal of the overvoltage or overcurrent, contact point 23a regains its position contact fixed contacting point piece 22. Preferably, switch 21 is positioned near the surge absorbing element 14 within housing 24. Figure 3 depicts a circuit diagram of the 20 embodiment of Figures 1 and 2. Leads 17, 13 and 19 are connected to the lines lla, llb and 12, respectively.
Numeral 13 designates the surge absorber.
The following tests illustrate the invention:
Test 1 A relatively large electric current at an overvoltage, i.e., an electric current of 40 A at 600 volts AC, is applied for 1.5 sec to communication or signal lines lla and 12 of the circuit shown in Figure 3. After a short time of 4 milliseconds from the start of the passing the current, heat is generated in bimetallic piece 23, and/or the surge protecting element, which radiates to piece 23.
As a result, bimetallic piece moves toward the surge absorber and point 23a moves away of contact with piece 22.
~ontact point 23a remains out of contact with piece 22 so long as the overvoltage is applied. When the overvol-tage is stopped, contactiny point 23a moves bac~ to contact fixed contact piece 22.
est 2 ~ relatively small electrîc curr0nt of an overvoltage, i.e., an electric current of 2.2 A at 600 volts AC, is applied to communic:ation lines lla and 12 of the circuit shown in F.igure 3 for 30 minutes. Cantacting point 23a moves repeatedly between the on (contact) and off (out-of-contact) positions due to the repeated actuation operations o~ bimetallic piece 23 caused by the heating or cooling of this element during the application of the overvoltage. The on (contact) period averages several milliseconds and the off (out-of-contact) period averages of 2 to 5 seconds.
In Tests 1 and 2, thermal damage or fire do not occur in the surge absorber and the electronic device used for the tests. Accordingly, since this surge absorber rapidly responds to -the continuous overvoltages or overcurrents and then disconnects the electronic circuit due to the thermal modification of the thermal response switch, thermal damage of the electronic devices caused by abnormal heating of the surge absorbing element due to the continuous overvoltages or overcurrents is avoided.
Furthermore, since the the.rmal response switch has a self-restoration function, this surge absorber can maintain itssurge suppression function and withstand continuous overvoltages or overcurrents without having to replace the thermal response switch. This results in a higher reliability and efficiency than observed with the conventional surge absorber.
;
Claims (9)
1. A surge absorber for protecting an electronic device having signal means connected thereto which comprises:
a) a surge absorbing element;
b) means for connecting the surge absorbing element to the signal means of the electronic device in parallel with the electronic device; and c) thermally activated means electrically connecting the signal means and the surge absorbing element which, in response to a given first temperature, connects the signal means with the surge absorbing element and the electronic device, and, in response to a higher, second temperature, disconnects the signal means from the surge absorbing element and the electronic device.
a) a surge absorbing element;
b) means for connecting the surge absorbing element to the signal means of the electronic device in parallel with the electronic device; and c) thermally activated means electrically connecting the signal means and the surge absorbing element which, in response to a given first temperature, connects the signal means with the surge absorbing element and the electronic device, and, in response to a higher, second temperature, disconnects the signal means from the surge absorbing element and the electronic device.
2. The surge absorber of claim 1 wherein the thermally activated means comprises a bimetallic switch adapted to interchange between an on and an off position depending on the temperature and positioned such that at the first, lower temperature, the switch is in the on position and the surge absorbing element is electrically connected with the signal means and at the second, higher temperature, the switch is in the off position and the surge absorbing element is disconnected from the signal means.
3. The surge absorber of claim 1 wherein the thermally activated means comprises a shape memorizing switch adapted to interchange between an on and an off positions depending on the temperature and positioned such that at the first, lower temperature, the switch is in the on position and the surge absorbing element is electrically connected with the signal means and at the second, higher temperature, the switch is in the off position and the surge absorbing element is disconnected from the signal means.
4. The surge absorber of claim 2 wherein the means connecting the surge absorbing element and the electronic device comprises a first, a second and a third lead, the surge absorbing element being connected between the second and third lead and the switch being connected between the first and second lead.
5. The surge absorber of claim 4 wherein the switch and the surge absorbing element are encased in a housing, a base of the housing being an insulating plate, the leads being secured to and penetrating through the insulating plate so as to be accessible from the exterior of the housing.
6. The surge absorber of claim 5 wherein the switch and the surge absorbing element are positioned sufficiently close to each other such that the switch is actuated by overheating of the surge absorbing element to the off position.
7. The surge absorber of claim 3, wherein the means connecting the surge absorbing element and the electronic device comprises a first, a second and a third lead, the surge absorbing element being connected between the second and third lead and the switch being connected between the first and second lead.
8. The surge absorber of claim 7, wherein the switch and the surge absorbing element are encased in a housing, a base of the housing being an insulating plate, the leads being secured to and penetrating through the insulating plate so as to be accessible from the exterior of the housing.
9. The surge absorber of claim 2, 3, or 8 wherein the switch and the surge absorbing element are positioned sufficiently close to each other such that the switch is actuated by overheating of the surge protector to the off position.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3028066A JPH04244732A (en) | 1991-01-29 | 1991-01-29 | Surge absorbing circuit and surge absorber formed thereof |
| JP3-28066 | 1991-01-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2060161A1 true CA2060161A1 (en) | 1992-07-30 |
Family
ID=12238394
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002060161A Abandoned CA2060161A1 (en) | 1991-01-29 | 1992-01-28 | Surge absorber |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH04244732A (en) |
| KR (1) | KR960000839B1 (en) |
| CA (1) | CA2060161A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100452855B1 (en) * | 2002-02-18 | 2004-10-14 | 텍사스 인스트루먼트 코리아 주식회사 | Motor protector |
| KR100820161B1 (en) * | 2003-12-22 | 2008-04-08 | 국방과학연구소 | Protective circuit of high voltage power supply |
| KR100899282B1 (en) * | 2006-07-18 | 2009-05-27 | 주식회사 엘지화학 | Safety Switch Using Heat Shrinkage Tube and Secondary Battery Including the Same |
| TWI669991B (en) | 2018-01-11 | 2019-08-21 | 和碩聯合科技股份有限公司 | Circuit board with electrostatic discharge protection mechanism and electronic apparatus having the same |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL8006411A (en) * | 1980-11-25 | 1982-06-16 | Philips Nv | DEVICE FOR PROTECTION AGAINST OVERHEATING BY OVERVOLTAGE OF A VOLTAGE LIMITING CIRCUIT. |
-
1991
- 1991-01-29 JP JP3028066A patent/JPH04244732A/en active Pending
-
1992
- 1992-01-27 KR KR1019920001139A patent/KR960000839B1/en not_active IP Right Cessation
- 1992-01-28 CA CA002060161A patent/CA2060161A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| KR960000839B1 (en) | 1996-01-13 |
| JPH04244732A (en) | 1992-09-01 |
| KR920015681A (en) | 1992-08-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |