CA1167918A - Electrical equipment protective apparatus with energy balancing among parallel varistors - Google Patents
Electrical equipment protective apparatus with energy balancing among parallel varistorsInfo
- Publication number
- CA1167918A CA1167918A CA000403929A CA403929A CA1167918A CA 1167918 A CA1167918 A CA 1167918A CA 000403929 A CA000403929 A CA 000403929A CA 403929 A CA403929 A CA 403929A CA 1167918 A CA1167918 A CA 1167918A
- Authority
- CA
- Canada
- Prior art keywords
- series
- varistor devices
- varistors
- resistors
- electrical equipment
- 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
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
- H01C7/12—Overvoltage protection resistors
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/16—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for capacitors
-
- 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
Abstract
49,409 ABSTRACT OF THE DISCLOSURE
Electrical equipment protection apparatus is provided comprising a plurality of varistor devices con-nected mutually in parallel, each of which exhibits a non-linear characteristic with an inherent differential in such characteristics, in combination with current sharing elements comprising a plurality of positive temperature coefficient resistors respectively associated with each of the non-linear resistors to ensure substantially equal current sharing among the plurality of varistors.
Electrical equipment protection apparatus is provided comprising a plurality of varistor devices con-nected mutually in parallel, each of which exhibits a non-linear characteristic with an inherent differential in such characteristics, in combination with current sharing elements comprising a plurality of positive temperature coefficient resistors respectively associated with each of the non-linear resistors to ensure substantially equal current sharing among the plurality of varistors.
Description
1 49,409 ELECTRICAL EQUIPMENT PROTECTIVE APPARATUS
WITH ENER5Y BALANCING AMONG PAP~L,LEL VARISTORS
BACKG~UND AND 5UMMARY OF THE INVENTION
This invention relates to protection apparatus for electrical equipment and particularly to protection of series capacitors.
Reference is made to U. S. Patent 4,295,174 issued October 13, 1981 by C. A. Peterson, et al.; and Canadian Serial No. 369,869, filed February 2, 1981 by C. A. P~terson, both of which are assigned to the present assignee, for background description ln relation to the application of non-linear resistors, particularly those of the metal oxide varistor type, to the protection of elec-trical power apparatus, particularly series capacitors.
Size, cost, and availa~ility constraints make it necessary to provide a plurality, frequently ten or more, varistor assemblies electrically in parallel across the equipment to be protected in order to obtain a sufficient level of current carrying capacity and energy absorption capability upon occurrence of a ~ault condition. It is intended that the various paralleled resistor assemblies have matching characteristics. Ideally, they would all turn on and become highly conductive upon the same overvoltage being impressed upon them. This would result in their common operation so that the current resulting from the applied voltage would be equally shared. I:f so, the design o~ the equipment would be relatively stralghtforward to provide a sufficient number of parallel units to handle the current , . . . . . .
. ~:
'' :' -,: , .-.
. .
3~
WITH ENER5Y BALANCING AMONG PAP~L,LEL VARISTORS
BACKG~UND AND 5UMMARY OF THE INVENTION
This invention relates to protection apparatus for electrical equipment and particularly to protection of series capacitors.
Reference is made to U. S. Patent 4,295,174 issued October 13, 1981 by C. A. Peterson, et al.; and Canadian Serial No. 369,869, filed February 2, 1981 by C. A. P~terson, both of which are assigned to the present assignee, for background description ln relation to the application of non-linear resistors, particularly those of the metal oxide varistor type, to the protection of elec-trical power apparatus, particularly series capacitors.
Size, cost, and availa~ility constraints make it necessary to provide a plurality, frequently ten or more, varistor assemblies electrically in parallel across the equipment to be protected in order to obtain a sufficient level of current carrying capacity and energy absorption capability upon occurrence of a ~ault condition. It is intended that the various paralleled resistor assemblies have matching characteristics. Ideally, they would all turn on and become highly conductive upon the same overvoltage being impressed upon them. This would result in their common operation so that the current resulting from the applied voltage would be equally shared. I:f so, the design o~ the equipment would be relatively stralghtforward to provide a sufficient number of parallel units to handle the current , . . . . . .
. ~:
'' :' -,: , .-.
. .
3~
2 -49,~09 produced and the energy required to be absorbed. In prac-tice, this ideal situation is not obtainable because of inherent small variations in characteristics of individual varistors. This re~uires a design involving an excess number of units to be applied to the protection equipment so as to provide the necessary insurance ~or proper func-- tioning. Any such excess units of course entails addi-tional cost which is desirably to be avoided.
The problem being addressed here is that of "energy balancing~' among the ~everal parallel varistor elements in the protective apparatus. The problem results from the slight manufacturing variability of characteris~
tics of the varistors, such as those essentially of zinc oxide and other metal oxides, which result in a large variation of current among parallel varistors under maxi-mum fault current conditions. The non-linearity charac-teristic of such device is expressed by the equation ln(I2/Il) ~ 1n(E2/El) in which the coefficient n represents the degree of non~
linearity. It is particularly difficult to fabricate a large number of resistor asse~blies in which the a values are exactly the same. The higher the a valu~, the hig~er the potential current imbalance among various resistors having the same variation in a. That is, for device of interest having an ~ of at least about 30, a variation in discharge voltage of +1%, which is about the practical limit of device fabrication in accordance with the present state of the art, may produce a current variation between parallel units of about 15-20%. This imbalance requires an extra margin of protective elements to be applied to the equipment to achieve the required overall energy absorption capability ~oughly speaking in terms of energy required to be absorbed, the~e may be required up to about 20% additional ~nergy absorption capability, as .
~ :'' . , ;' . . , : ~ , .D~ 8
The problem being addressed here is that of "energy balancing~' among the ~everal parallel varistor elements in the protective apparatus. The problem results from the slight manufacturing variability of characteris~
tics of the varistors, such as those essentially of zinc oxide and other metal oxides, which result in a large variation of current among parallel varistors under maxi-mum fault current conditions. The non-linearity charac-teristic of such device is expressed by the equation ln(I2/Il) ~ 1n(E2/El) in which the coefficient n represents the degree of non~
linearity. It is particularly difficult to fabricate a large number of resistor asse~blies in which the a values are exactly the same. The higher the a valu~, the hig~er the potential current imbalance among various resistors having the same variation in a. That is, for device of interest having an ~ of at least about 30, a variation in discharge voltage of +1%, which is about the practical limit of device fabrication in accordance with the present state of the art, may produce a current variation between parallel units of about 15-20%. This imbalance requires an extra margin of protective elements to be applied to the equipment to achieve the required overall energy absorption capability ~oughly speaking in terms of energy required to be absorbed, the~e may be required up to about 20% additional ~nergy absorption capability, as .
~ :'' . , ;' . . , : ~ , .D~ 8
3 4g,409 compared to an ideal case of precisely matched character-istics, which results in a requirement of 20% additional pounds of varistor material and related cost.
The purposes of this invention have to do with being able to tolerate the inherent variation of charac-teristics betw2en relatively well made metal oxid~ varist-or units and at the same time being able to utilize fewer such units in achi~ving th~ reguired functional perfor-mance for the protection of high voltage equipment such as series capacitors.
Briefly, the invention achieves the foregoing objectives by connecting a resistor having a positive temperature coefficient (PTC) of resistance in series with each of the varistor assemblies. The resistor el0ments, which may comprise merely a wire of material such as Nichrome alloy, will under'fault condition ~ heat up and increase in resistance as a function of I2t through each of the respective varistors. Therefore, a varistor whose inherent characteristics are such that it would tend on its own to carry more current than another parallel var-istor, would heat the wire up more and cause an increase in the resistance of the affect~d series connected wire.
This would reduce the current flow to the affected var-ist~r and shift the current to adjacent varistors that have lower impedance. The current and the conse~uent joules of energy would therefore be forced dynamically to be shared among all of the parallel assemblies. This ensures again~t overburdening an individual assembly which could result in damage to it.
The invention is attractive for application to protecting series capacitors because they normally require a relatively large number of varistors. It is desirable that the selection of the individual voltage limiters be not critical as to the slope of their non-linear voltage-current characteri~tic and hence the invention will reduce the matching and testing of zinc oxide llmiter units as well as minimize the numbers thereof re~uired in the total .
~ ;?~ t~
~ .49,409 assembly. Also, the positive tempera~ure coefficient resistance wire employed can be readily incorporated in the equipment at relatively 1GW cost. rrhe PTC will intro-duce almost no losses u~der normal operating condition~
because the current through the varistor~resistor combin-ation will be less than a milliampere.
Although this application of the PTC resistors will result in a slight reduction of the a value of the series combination of the wire and the varistor (e.g.
2-4%), a result which is unfavorable in itself, a point can be selected at which the tradeoff is very favorable because the higher the resistance of the connected series wire, the greater is the energy balancing ~ffect. For example, the energy balance may be improved -~ i30% to +10%.
BRIEF DESCRIPTION OE THE DRAWINGS
The single Figure is a general schematic circuit diagram of a series capacitor and protection eguipment therefore in accord~nce with the present invention.
DESCRIPTION OE T~E PREFERRED EMBODIMENT
Referring to the Figure, a series capacitor 10, which may be any part of or a complete series capacitor bank, is shown connected in series with a transmission line between a yenerator and a load. Protection equipment comprising a plurality of parallel non-linear, preferably metal oxide, varistors 14A, 14B, 14C and 14D, is connected across the series capacitor 10. The non-linear resistors 14A through 14D have the inherent capability of reaching turn on upon the application of a certain overvoltage, as may result from a fault on the transmission line 12. The overvoltage could cause damage to the capacitor unless bypassed by the non-linear elements. As was discussed in the background portion above, the capability of available devices is such that there is an i~herent variation in the discharge voltage of the various paralleled units and it is therefore difficult to ensure egual current sharing among them if only the varistors14A, 14B, 14C and 14D are connected in the paralleled circuit branches.
4g,40g The Figure shows an embodimenk of the present invention in which each of the metal oxide varistor assem-blies 14A through 14D that are paralleled ~cross the protected capacitor 10, or other electrical equipmen-t, have in series with them a respective resistor 16A through 16D which is selected to be of the poYitive temperature coefficient IPTC) type. The resistor may be provided as a wire connecting the metal oxide assembly to the main terminals and may be of a material such as Nichrome alloy.
The effect of the PTC resistors 16A through 16D is that as the wire temperature increases due to the amount o cur-rent conducted by its series connected metal oxide unit, the resistance of the wire will increase resulting in reduction of current flow through that varistor. The current Will be shifted to adjacent assemblies that have lower impedance resulting in an overall balancing. The joules of energy to be absorbed will by this technique be forced dynamically to the assemblies that have lower current through them and, hence, available energy absorb-ing capacity.
The wire, or other elements for resistors 16A-16D, will be selected in accordance with the non-linear capability a~d the voltage-ampere characteristic of the non-linear resistors. The tradeoff is that the higher the resistance of the wire, the greater the energy balancing effect of the device. The greater resistance, however, has the effect of reducing the ~ value of the series combination of ~he wire and non-linear resistor. The resistors 16A-16D and ~ temperature coefficient of change will be selected to give a certain temperature rise that results in the desired change in resistance for the level o I2t required in order to transfer current to adjacent parallel units. It is suitable in most instances for the Nichrome wire or other PTC resistors 16A-16D to 5 have a resistance value of the order of 1% of the maximum ~3rQ.
(~ffl~-turn on) resistance o the varistors 14A-14D.
- .:
The purposes of this invention have to do with being able to tolerate the inherent variation of charac-teristics betw2en relatively well made metal oxid~ varist-or units and at the same time being able to utilize fewer such units in achi~ving th~ reguired functional perfor-mance for the protection of high voltage equipment such as series capacitors.
Briefly, the invention achieves the foregoing objectives by connecting a resistor having a positive temperature coefficient (PTC) of resistance in series with each of the varistor assemblies. The resistor el0ments, which may comprise merely a wire of material such as Nichrome alloy, will under'fault condition ~ heat up and increase in resistance as a function of I2t through each of the respective varistors. Therefore, a varistor whose inherent characteristics are such that it would tend on its own to carry more current than another parallel var-istor, would heat the wire up more and cause an increase in the resistance of the affect~d series connected wire.
This would reduce the current flow to the affected var-ist~r and shift the current to adjacent varistors that have lower impedance. The current and the conse~uent joules of energy would therefore be forced dynamically to be shared among all of the parallel assemblies. This ensures again~t overburdening an individual assembly which could result in damage to it.
The invention is attractive for application to protecting series capacitors because they normally require a relatively large number of varistors. It is desirable that the selection of the individual voltage limiters be not critical as to the slope of their non-linear voltage-current characteri~tic and hence the invention will reduce the matching and testing of zinc oxide llmiter units as well as minimize the numbers thereof re~uired in the total .
~ ;?~ t~
~ .49,409 assembly. Also, the positive tempera~ure coefficient resistance wire employed can be readily incorporated in the equipment at relatively 1GW cost. rrhe PTC will intro-duce almost no losses u~der normal operating condition~
because the current through the varistor~resistor combin-ation will be less than a milliampere.
Although this application of the PTC resistors will result in a slight reduction of the a value of the series combination of the wire and the varistor (e.g.
2-4%), a result which is unfavorable in itself, a point can be selected at which the tradeoff is very favorable because the higher the resistance of the connected series wire, the greater is the energy balancing ~ffect. For example, the energy balance may be improved -~ i30% to +10%.
BRIEF DESCRIPTION OE THE DRAWINGS
The single Figure is a general schematic circuit diagram of a series capacitor and protection eguipment therefore in accord~nce with the present invention.
DESCRIPTION OE T~E PREFERRED EMBODIMENT
Referring to the Figure, a series capacitor 10, which may be any part of or a complete series capacitor bank, is shown connected in series with a transmission line between a yenerator and a load. Protection equipment comprising a plurality of parallel non-linear, preferably metal oxide, varistors 14A, 14B, 14C and 14D, is connected across the series capacitor 10. The non-linear resistors 14A through 14D have the inherent capability of reaching turn on upon the application of a certain overvoltage, as may result from a fault on the transmission line 12. The overvoltage could cause damage to the capacitor unless bypassed by the non-linear elements. As was discussed in the background portion above, the capability of available devices is such that there is an i~herent variation in the discharge voltage of the various paralleled units and it is therefore difficult to ensure egual current sharing among them if only the varistors14A, 14B, 14C and 14D are connected in the paralleled circuit branches.
4g,40g The Figure shows an embodimenk of the present invention in which each of the metal oxide varistor assem-blies 14A through 14D that are paralleled ~cross the protected capacitor 10, or other electrical equipmen-t, have in series with them a respective resistor 16A through 16D which is selected to be of the poYitive temperature coefficient IPTC) type. The resistor may be provided as a wire connecting the metal oxide assembly to the main terminals and may be of a material such as Nichrome alloy.
The effect of the PTC resistors 16A through 16D is that as the wire temperature increases due to the amount o cur-rent conducted by its series connected metal oxide unit, the resistance of the wire will increase resulting in reduction of current flow through that varistor. The current Will be shifted to adjacent assemblies that have lower impedance resulting in an overall balancing. The joules of energy to be absorbed will by this technique be forced dynamically to the assemblies that have lower current through them and, hence, available energy absorb-ing capacity.
The wire, or other elements for resistors 16A-16D, will be selected in accordance with the non-linear capability a~d the voltage-ampere characteristic of the non-linear resistors. The tradeoff is that the higher the resistance of the wire, the greater the energy balancing effect of the device. The greater resistance, however, has the effect of reducing the ~ value of the series combination of ~he wire and non-linear resistor. The resistors 16A-16D and ~ temperature coefficient of change will be selected to give a certain temperature rise that results in the desired change in resistance for the level o I2t required in order to transfer current to adjacent parallel units. It is suitable in most instances for the Nichrome wire or other PTC resistors 16A-16D to 5 have a resistance value of the order of 1% of the maximum ~3rQ.
(~ffl~-turn on) resistance o the varistors 14A-14D.
- .:
Claims (6)
1. Electrical equipment overvoltage protection apparatus comprising:
a plurality of varistor devices connected mutually in parallel for connection across the protected electrical equipment, each of said varistor devices exhibiting a drop in resistance value to become highly conductive upon application of a voltage of a magnitude that would be injurious to the protected electrical equipment, the total number of said plurality of varistor devices being sufficient to absorb without damage the energy associated with an anticipated fault current; and, current sharing means connected with said plurality of varistor devices for insuring approximate equality of cur-rent conducted, and hence energy absorption required, by respective ones of said plurality of varistor devices despite inherent variation in the conduction characteristics of the varistor devices themselves;
said current sharing means comprising a plurality of resistors connected respectively in series with said plurality of varistor devices, said resistors each having a positive temperature coefficient of resistance so a more highly con-ductive one of said varistor devices is relieved of excessive current by the resistive heating of the resistive connected in series with it to force current to another, less highly con-ductive, one of said varistor devices.
7 49,409
a plurality of varistor devices connected mutually in parallel for connection across the protected electrical equipment, each of said varistor devices exhibiting a drop in resistance value to become highly conductive upon application of a voltage of a magnitude that would be injurious to the protected electrical equipment, the total number of said plurality of varistor devices being sufficient to absorb without damage the energy associated with an anticipated fault current; and, current sharing means connected with said plurality of varistor devices for insuring approximate equality of cur-rent conducted, and hence energy absorption required, by respective ones of said plurality of varistor devices despite inherent variation in the conduction characteristics of the varistor devices themselves;
said current sharing means comprising a plurality of resistors connected respectively in series with said plurality of varistor devices, said resistors each having a positive temperature coefficient of resistance so a more highly con-ductive one of said varistor devices is relieved of excessive current by the resistive heating of the resistive connected in series with it to force current to another, less highly con-ductive, one of said varistor devices.
7 49,409
2. Electrical equipment overvoltage protection apparatus in accordance with claim 1 wherein:
said resistors each comprise a wire connected in series with one of said varistor devices and having a positive temperature coefficient of resistance.
said resistors each comprise a wire connected in series with one of said varistor devices and having a positive temperature coefficient of resistance.
3. electrical equipment overvoltage protection apparatus in accordance with claim 1 wherein:
4. Series capacitor equipment comprising:
capacitor equipment for connection in series with a high voltage transmission line;
protection apparatus for said capacitor equip-ment to protect against damage due to excessive voltage appearing thereacross and comprising a plurality of var-istors having substantially equal breakdown voltage char-acteristics but with some inherent variation therebetween, connected mutually in parallel across said capacitor equipment, each of said plurality of varistors being connected in series with respective ones of a plurality of resistors having a positive temperature coefficient of resistance to insure substantially equal current sharing among said plurality of varistors.
capacitor equipment for connection in series with a high voltage transmission line;
protection apparatus for said capacitor equip-ment to protect against damage due to excessive voltage appearing thereacross and comprising a plurality of var-istors having substantially equal breakdown voltage char-acteristics but with some inherent variation therebetween, connected mutually in parallel across said capacitor equipment, each of said plurality of varistors being connected in series with respective ones of a plurality of resistors having a positive temperature coefficient of resistance to insure substantially equal current sharing among said plurality of varistors.
5. Series capacitor equipment in accordance with claim 4 wherein each of said plurality of varistors comprises at least one metal oxide element having a non-linearity in its voltage-current characteristic.
6. series capacitor equipment in accordance with claim 5 wherein said plurality of varistors said said plurality of resistors are directly connected across said capacitor equipment without any spark gap discharge device in series herewith.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US270,176 | 1981-06-03 | ||
| US06/270,176 US4347539A (en) | 1981-06-03 | 1981-06-03 | Electrical equipment protective apparatus with energy balancing among parallel varistors |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1167918A true CA1167918A (en) | 1984-05-22 |
Family
ID=23030224
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000403929A Expired CA1167918A (en) | 1981-06-03 | 1982-05-27 | Electrical equipment protective apparatus with energy balancing among parallel varistors |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4347539A (en) |
| CA (1) | CA1167918A (en) |
Families Citing this family (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59105226A (en) * | 1982-12-09 | 1984-06-18 | 株式会社日立製作所 | Breaker |
| SE449151B (en) * | 1983-06-17 | 1987-04-06 | Asea Ab | PROTECTIVE DEVICE FOR A SERIES CONDENSER |
| SE452823B (en) * | 1984-03-07 | 1987-12-14 | Asea Ab | Series capacitor EQUIPMENT |
| US4807081A (en) * | 1986-09-05 | 1989-02-21 | Raychem Limited | Circuit protection arrangement |
| FR2631156B1 (en) * | 1988-05-06 | 1994-07-22 | Signaux Equip Electroniques | CAPACITIVE TYPE ELECTRIC ENERGY ACCUMULATOR, LARGE CAPACITY |
| DE4142523A1 (en) * | 1991-12-21 | 1993-06-24 | Asea Brown Boveri | RESISTANCE WITH PTC BEHAVIOR |
| EP0649150B1 (en) * | 1993-10-15 | 1998-06-24 | Abb Research Ltd. | Composite material |
| AUPO605397A0 (en) * | 1997-04-07 | 1997-05-01 | Erico Lightning Technologies Pty Ltd | Improvements in transient overvoltage and lightning protection of power connected equipment |
| US6226166B1 (en) | 1997-11-28 | 2001-05-01 | Erico Lighting Technologies Pty Ltd | Transient overvoltage and lightning protection of power connected equipment |
| US6128168A (en) * | 1998-01-14 | 2000-10-03 | General Electric Company | Circuit breaker with improved arc interruption function |
| GB2345187A (en) * | 1998-12-24 | 2000-06-28 | Telematic Ltd | Metal oxide varistors |
| US6144540A (en) * | 1999-03-09 | 2000-11-07 | General Electric Company | Current suppressing circuit breaker unit for inductive motor protection |
| US6157286A (en) * | 1999-04-05 | 2000-12-05 | General Electric Company | High voltage current limiting device |
| US6930871B2 (en) * | 1999-11-19 | 2005-08-16 | Citel | Lightning arrester device for low-voltage network |
| US20050083628A1 (en) * | 2003-10-17 | 2005-04-21 | Holzenthal Leo L.Jr. | Close tolerance surge suppression circuit |
| CN103001201A (en) * | 2011-09-13 | 2013-03-27 | 黄岩 | Method and device for suppressing high-energy surge |
| WO2015046258A1 (en) * | 2013-09-25 | 2015-04-02 | タイコエレクトロニクスジャパン合同会社 | Protection device |
| WO2015092553A2 (en) * | 2013-12-18 | 2015-06-25 | Ingeteam Power Technology, S.A. | Variable impedance device for a wind turbine |
| DE102014210797A1 (en) * | 2014-06-05 | 2015-12-17 | Osram Gmbh | Circuit arrangement for converting voltages |
| CN104836218A (en) * | 2015-06-01 | 2015-08-12 | 合肥扬帆通信元器件有限公司 | High-capacity overvoltage absorber |
| CN112563030B (en) * | 2020-12-01 | 2022-02-15 | 上海上电电容器有限公司 | Non-inductive voltage-sharing damping voltage-dividing capacitor |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH218209A (en) * | 1941-06-20 | 1941-11-30 | Bbc Brown Boveri & Cie | Surge arresters. |
| US3254290A (en) * | 1963-01-16 | 1966-05-31 | Westinghouse Electric Corp | Protective means for rectifier apparatus |
| US3246206A (en) * | 1965-02-25 | 1966-04-12 | Gen Electric | Voltage surge protector |
| GB1163795A (en) * | 1967-06-02 | 1969-09-10 | Ass Elect Ind | Over-Voltage Protection Circuit |
| SE352992B (en) * | 1967-11-06 | 1973-01-15 | Asea Ab | |
| US3662250A (en) * | 1970-11-12 | 1972-05-09 | Gen Electric | Thyristor overvoltage protective circuit |
| US3894274A (en) * | 1974-07-01 | 1975-07-08 | Gen Electric | Electric motor transient voltage suppressing circuit |
| US3947726A (en) * | 1974-12-18 | 1976-03-30 | General Electric Co. | Reverse voltage surge protection for high-voltage thyristors |
| CH586483A5 (en) * | 1975-01-16 | 1977-03-31 | Bbc Brown Boveri & Cie | |
| US4023071A (en) * | 1975-06-09 | 1977-05-10 | Fussell Gerald W | Transient and surge protection apparatus |
| US4068281A (en) * | 1976-09-15 | 1978-01-10 | General Electric Company | Thermally responsive metal oxide varistor transient suppression circuit |
| US4152743A (en) * | 1977-06-27 | 1979-05-01 | Comstock Wilford K | Transient voltage suppression system |
-
1981
- 1981-06-03 US US06/270,176 patent/US4347539A/en not_active Expired - Lifetime
-
1982
- 1982-05-27 CA CA000403929A patent/CA1167918A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4347539A (en) | 1982-08-31 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |