WO2010126453A1 - A varistor with a defined weak spot in the structure - Google Patents
A varistor with a defined weak spot in the structure Download PDFInfo
- Publication number
- WO2010126453A1 WO2010126453A1 PCT/SI2010/000022 SI2010000022W WO2010126453A1 WO 2010126453 A1 WO2010126453 A1 WO 2010126453A1 SI 2010000022 W SI2010000022 W SI 2010000022W WO 2010126453 A1 WO2010126453 A1 WO 2010126453A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- varistor
- weak spot
- intentionally incorporated
- spot
- intentionally
- Prior art date
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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
- H01C7/102—Varistor boundary, e.g. surface layers
-
- 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
- H01C7/126—Means for protecting against excessive pressure or for disconnecting in case of failure
Definitions
- the invention relates to a varistor with an intentionally defined and positionally determined weak spot on and in the structure of varistors with the fundamental purpose of upgrading a varistor with a thermal cut-off in overvoltage protection modules.
- a technical problem solved by the present invention is a constructional solution to a varistor that will be provided with an intentionally defined and positionally determined weak spot. Combined with a thermal cut-off, the intentionally defined and positionally determined weak spot will allow for precisely defined, quick, efficient and safe cut-offs of protection modules and their protection against total destruction in case of excessive electrical overloads.
- the invention solves positioning of an intentionally incorporated weak spot and defining its effect for a minimum needed yield that exceeds a natural non-homogeneity of a structure and does simultaneously not weaken the generally defined energy absorption of a varistor.
- Varistors are passive components preferably manufactured from a ceramic material like zinc oxide with additives of other metal oxides. They dispose over a specific nonlinear U/l characteristic that is very similar to the characteristic of a double Zener diode, yet with a considerably more powerful current absorption. They are mainly used in overvoltage protective devices. As elements having a limiting characteristic, they have to absorb the energy produced in cases of electrical overloads in the form of overvoltage or current surges and limit the voltage to a non-dangerous level that is no longer harmful for components, devices or systems they protect.
- Limitation of voltage is not the only characteristic of varistors, one of the most important characteristics is also their capability of absorbing energy, i.e. the energy that a varistor can still accept before total destruction. It is measured and indicated in the form of current absorption in [kA] for short-term pulse forms or in the form of temporary overvoltage [V] in case of defects in infrastructure systems, in which they are integrated. Energy received in all cases of electrical overloads regardless of their origin is converted to heat energy and it depends on a varistor structure, how the temperature will distribute over the structure. The current running through the body of a varistor is generally distributed unequally and in a non-defined way as a consequence of a technological process.
- the essence of a varistor with a defined weak spot in the structure lies in that local overheating is determined in advance on a precisely selected place on the body of a varistor, which does not impair energy absorption of a varistor.
- An incorporated weak spot in the structure of the body of a varistor may have a shape of a circle, rectangle or any other geometrical shape.
- the number of intentionally incorporated weak spots is optional as well. In case of several weak spots in the structure of the body of a varistor, they are of the same geometrical shape or have a combination of various geometrical shapes.
- Figure 1 presentation of various shapes of intentionally incorporated weak spots in the body of a varistor of the invention
- Figure 2 Temperature gradient (5) in the intentionally incorporated weak spots in the body of a varistor compared to gradient of average temperature (6) of the body of a varistor upon absorption of a current surge.
- a varistor with a defined weak spot in the structure is characterized in that a circular weak spot 2 with a deepening 2a is arranged in a body 1.
- the location on the body is optionally selected depending on the size of a varistor. Energy absorption of a varistor is not impaired despite the weak spot 2 where local overheating of the body of the varistor occurs.
- the varistor of the present invention reaches the fundamental purpose, namely when current flows through the varistor regardless of the cause of appearance of that current, a somewhat stronger current flows through the weak spot 2 of the body 1 of the varistor than through the remaining structure.
- the process of adequate distribution of current is triggered within the defined incorporated weak spot 2 of the varistor, the process of adequate local heating is started, which gets expanded over the entire body of the varistor due to a high conductivity coefficient.
- the temperature very quickly transfers from the location of the intentionally incorporated weak spot 2 over the entire body of the varistor, wherein in cases of long-lasting overloads the intentionally incorporated weak spot 2 functions as a relatively permanent source of temperature, which allows the superstructure thermal cut-off system to adequately react and to physically disconnect from the system.
- the weak spot representing a hot spot is a precisely defined selected location or several locations on the surface or within the varistor, where, in case of electrical overloads, the temperature of the varistor increases considerably more quickly than on the remaining part of the varistor and is on the average higher between 10 % and 40 %.
- the intentionally defined weak spot 2 may be located on any part of the body 1 and is of a circular shape having a diameter of 1 mm to 15 mm, which represents from 0.05 % to 60 % of the entire surface of the body 1.
- the deepening 2a of the spot 2 amounts to 0.1 mm to 1 mm, which is from 0.1 % to 30 % of the entire thickness of the body 1 of the varistor.
- the material intended for the spot 2 is a material similar to the basic ingredient of the varistor material, most often ZnO and adequate dopants, and is embedded in the basic varistor ceramic during a technological process.
- the intentionally defined weak or hot spot is a precisely controlled anomaly as to standard or typical shapes of varistors known in prior art.
- a controlled anomaly can be defined as any change on the surface with respect to the normal level to the depth or in height based on the reference (type) level.
- the varistor of the invention comprises a process for the introduction of an intentionally defined weak spot of the varistor on the surface or within the varistor, or in combination of both, on a precisely defined location, which is technologically defined and allows for an anticipation of a weak spot in case of electrical overloads. Since said spot gets considerably more heated in comparison with the remaining part of the body of the varistor in case of electrical overloads, this spot is also called a hot spot.
- a varistor with a defined weak spot in the structure according to variant I is characterized in that there is a weak spot 3 of a rectangular shape with a deepening 3a arranged on a body 1 of the varistor and the surface of the intentionally incorporated weak spot 3 on the surface of the body 1 of the varistor lies in the range from 0.05 % to 60 % of the entire surface of the varistor.
- a varistor with a defined weak spot in the structure according to variant Il is characterized in that a weak spot 4 is a foreign material embedded in a body 1.
- the foreign material is formed by inserting substances of organic or inorganic origin into the depth of the varistor on any part of the body of the varistor in similar geometrical proportions as in the varistor according to variant I.
- a characteristic of the varistor with the intentionally incorporated weak spot in the structure of the invention as well as of the varistors according to variants I and II lies in that temperature on the location with the intentionally incorporated weak spot increases by 10 % to 40 % more quickly in case of electrical overload than on the remaining parts of the body of the varistor.
- the varistor with the intentionally incorporated weak spot in the structure is characterized in that the surface of the intentionally incorporated weak spot on the surface of the body of the varistor lies in the range from 0.05 % to 60 % of the entire surface of the varistor.
- the varistor with the intentionally incorporated weak spot in the structure is characterized in that the intentionally incorporated weak spot is arranged at a depth of 0.1 to 1 mm or 0.1 % to 30 % of the thickness of the body of the varistor.
- the varistor with the intentionally incorporated weak spot in the structure may have an optional number of intentionally incorporated weak spots.
- the varistor with the intentionally incorporated weak spot in the structure may have an intentionally incorporated weak spot in an optional geometrical shape.
- defined incorporated weak spots are arranged on the surface, where they may have a shape of a circle or any other geometrical shape.
- Intentionally incorporated weak spots or anomalies comprise all changes made on the surface of the body of the varistor that deviate from the requirements of the principles of good industrial practice for a homogeneous material, without foreign material and bubbles.
Abstract
The invention relates to varistors with an intentionally defined and positionally determined weak spot on and in the structure of varistors with the fundamental purpose of upgrading a varistor with a thermal cut-off in overvoltage protection modules. The varistor with an intentionally incorporated weak spot in the structure according to Claim 1 is characterized in that a weak spot (2) of a circular shape with a deepening (2a) is arranged in a body (1) of the varistor and the location on the body (1) can be optionally selected depending on the size of the varistor. Energy absorption of a varistor is not impaired despite the weak spot (2) where local overheating of the body (1) occurs. A somewhat stronger current flows through the weak spot (2) of the body (1) of the varistor, when current flows through the varistor regardless of the cause of appearance of that current. Upon a process of adequate distribution of current through the varistor the latter is triggered within the defined incorporated weak spot (2) of the varistor and a process of adequate local heating is started, which gets expanded over the entire body (1) of the varistor due to a high conductivity coefficient. In case of huge, yet short-term electrical overloads, the temperature very quickly transfers from the location of the weak spot (2) over the entire body (1) of the varistor, wherein in cases of long-lasting overloads the intentionally incorporated weak spot (2) functions as a relatively permanent source of temperature, which allows the superstructure thermal cut-off system to adequately react and to physically disconnect from the system.
Description
A VARISTOR WITH A DEFINED WEAK SPOT IN THE STRUCTURE
Field of the Invention
The invention relates to a varistor with an intentionally defined and positionally determined weak spot on and in the structure of varistors with the fundamental purpose of upgrading a varistor with a thermal cut-off in overvoltage protection modules.
Technical Problem
A technical problem solved by the present invention is a constructional solution to a varistor that will be provided with an intentionally defined and positionally determined weak spot. Combined with a thermal cut-off, the intentionally defined and positionally determined weak spot will allow for precisely defined, quick, efficient and safe cut-offs of protection modules and their protection against total destruction in case of excessive electrical overloads. The invention solves positioning of an intentionally incorporated weak spot and defining its effect for a minimum needed yield that exceeds a natural non-homogeneity of a structure and does simultaneously not weaken the generally defined energy absorption of a varistor.
Prior Art
Varistors are passive components preferably manufactured from a ceramic material like zinc oxide with additives of other metal oxides. They dispose over a specific nonlinear U/l characteristic that is very similar to the characteristic of a double Zener diode, yet with a considerably more powerful current absorption. They are mainly used in overvoltage protective devices. As elements having a limiting characteristic, they have to absorb the energy produced in cases of electrical overloads in the form
of overvoltage or current surges and limit the voltage to a non-dangerous level that is no longer harmful for components, devices or systems they protect.
Limitation of voltage is not the only characteristic of varistors, one of the most important characteristics is also their capability of absorbing energy, i.e. the energy that a varistor can still accept before total destruction. It is measured and indicated in the form of current absorption in [kA] for short-term pulse forms or in the form of temporary overvoltage [V] in case of defects in infrastructure systems, in which they are integrated. Energy received in all cases of electrical overloads regardless of their origin is converted to heat energy and it depends on a varistor structure, how the temperature will distribute over the structure. The current running through the body of a varistor is generally distributed unequally and in a non-defined way as a consequence of a technological process.
All solutions from prior art are directed to an ideal varistor structure both on the material preparation level and in the manufacturing process. There are quite a few solutions intended to discover defects in a material and solutions aimed at supervising the manufacturing process in order to make precaution in eliminating all risks related to potential defects occurring in the structure of the body of a varistor. However, certain natural anomalies are always present in a manufacturing process and therefore no ideal homogeneity can be reached in any case, which results in an unequal distribution of current and in local overheating.
Available documents provided no solutions for a purposeful creation of weak spots or other anomalies in a structure of the body of a varistor on predetermined spots on the surface or within the body of the varistor and herewith linked solutions to an efficient definition of a weak or hot spot.
Description of the Solution
The essence of a varistor with a defined weak spot in the structure lies in that local overheating is determined in advance on a precisely selected place on the body of a varistor, which does not impair energy absorption of a varistor. An incorporated weak spot in the structure of the body of a varistor may have a shape of a circle, rectangle or any other geometrical shape. The number of intentionally incorporated weak spots is optional as well. In case of several weak spots in the structure of the body of a varistor, they are of the same geometrical shape or have a combination of various geometrical shapes.
A varistor with a defined weak spot in the structure will be described in the continuation by way of drawings, representing in:
Figure 1 - presentation of various shapes of intentionally incorporated weak spots in the body of a varistor of the invention Figure 2 - Temperature gradient (5) in the intentionally incorporated weak spots in the body of a varistor compared to gradient of average temperature (6) of the body of a varistor upon absorption of a current surge.
A varistor with a defined weak spot in the structure is characterized in that a circular weak spot 2 with a deepening 2a is arranged in a body 1. The location on the body is optionally selected depending on the size of a varistor. Energy absorption of a varistor is not impaired despite the weak spot 2 where local overheating of the body of the varistor occurs. The varistor of the present invention reaches the fundamental purpose, namely when current flows through the varistor regardless of the cause of appearance of that current, a somewhat stronger current flows through the weak spot 2 of the body 1 of the varistor than through the remaining structure. As the process of adequate distribution of current is triggered within the defined incorporated weak spot 2 of the varistor, the process of adequate local heating is started, which gets
expanded over the entire body of the varistor due to a high conductivity coefficient. In case of huge, yet short-term electrical overloads, the temperature very quickly transfers from the location of the intentionally incorporated weak spot 2 over the entire body of the varistor, wherein in cases of long-lasting overloads the intentionally incorporated weak spot 2 functions as a relatively permanent source of temperature, which allows the superstructure thermal cut-off system to adequately react and to physically disconnect from the system.
The weak spot representing a hot spot is a precisely defined selected location or several locations on the surface or within the varistor, where, in case of electrical overloads, the temperature of the varistor increases considerably more quickly than on the remaining part of the varistor and is on the average higher between 10 % and 40 %.
The intentionally defined weak spot 2 may be located on any part of the body 1 and is of a circular shape having a diameter of 1 mm to 15 mm, which represents from 0.05 % to 60 % of the entire surface of the body 1. The deepening 2a of the spot 2 amounts to 0.1 mm to 1 mm, which is from 0.1 % to 30 % of the entire thickness of the body 1 of the varistor. The material intended for the spot 2 is a material similar to the basic ingredient of the varistor material, most often ZnO and adequate dopants, and is embedded in the basic varistor ceramic during a technological process.
Technologically speaking, the intentionally defined weak or hot spot is a precisely controlled anomaly as to standard or typical shapes of varistors known in prior art. A controlled anomaly can be defined as any change on the surface with respect to the normal level to the depth or in height based on the reference (type) level.
The varistor of the invention comprises a process for the introduction of an intentionally defined weak spot of the varistor on the surface or within the varistor, or in combination of both, on a precisely defined location, which is technologically
defined and allows for an anticipation of a weak spot in case of electrical overloads. Since said spot gets considerably more heated in comparison with the remaining part of the body of the varistor in case of electrical overloads, this spot is also called a hot spot.
A varistor with a defined weak spot in the structure according to variant I is characterized in that there is a weak spot 3 of a rectangular shape with a deepening 3a arranged on a body 1 of the varistor and the surface of the intentionally incorporated weak spot 3 on the surface of the body 1 of the varistor lies in the range from 0.05 % to 60 % of the entire surface of the varistor.
A varistor with a defined weak spot in the structure according to variant Il is characterized in that a weak spot 4 is a foreign material embedded in a body 1. The foreign material is formed by inserting substances of organic or inorganic origin into the depth of the varistor on any part of the body of the varistor in similar geometrical proportions as in the varistor according to variant I.
A characteristic of the varistor with the intentionally incorporated weak spot in the structure of the invention as well as of the varistors according to variants I and II lies in that temperature on the location with the intentionally incorporated weak spot increases by 10 % to 40 % more quickly in case of electrical overload than on the remaining parts of the body of the varistor.
The varistor with the intentionally incorporated weak spot in the structure is characterized in that the surface of the intentionally incorporated weak spot on the surface of the body of the varistor lies in the range from 0.05 % to 60 % of the entire surface of the varistor.
The varistor with the intentionally incorporated weak spot in the structure is characterized in that the intentionally incorporated weak spot is arranged at a depth of 0.1 to 1 mm or 0.1 % to 30 % of the thickness of the body of the varistor.
The varistor with the intentionally incorporated weak spot in the structure may have an optional number of intentionally incorporated weak spots.
The varistor with the intentionally incorporated weak spot in the structure may have an intentionally incorporated weak spot in an optional geometrical shape. Defined incorporated weak spots are arranged on the surface, where they may have a shape of a circle or any other geometrical shape. Intentionally incorporated weak spots or anomalies comprise all changes made on the surface of the body of the varistor that deviate from the requirements of the principles of good industrial practice for a homogeneous material, without foreign material and bubbles.
Claims
1. A varistor with an intentionally incorporated weak spot in the structure comprising the basic material ZnO and adequate dopants is characterized in that it has an intentionally incorporated weak spot that may be arranged on the surface or within the body of the varistor.
2. Varistor with an intentionally incorporated weak spot in the structure as claimed in Claim 1 , characterized in that a weak spot (2) of a circular shape with a deepening (2a) is arranged in a body (1) of the varistor, that the location on the body (1) can be optionally selected depending on the size of the varistor, that energy absorption of a varistor is not impaired despite the weak spot (2) where local overheating of the body (1) of the varistor occurs, that a somewhat stronger current flows through the weak spot (2) of the body (1) of the varistor, when current flows through the varistor regardless of the cause of appearance of that current, that upon a process of adequate distribution of current through the varistor the latter is triggered within the defined incorporated weak spot (2) of the varistor, that a process of adequate local heating is started, which gets expanded over the entire body (1) of the varistor due to a high conductivity coefficient, that in case of huge, yet short-term electrical overloads, the temperature very quickly transfers from the location of the intentionally incorporated weak spot (2) over the entire body (1) of the varistor, wherein in cases of long-lasting overloads the intentionally incorporated weak spot (2) functions as a relatively permanent source of temperature, which allows the superstructure thermal cut-off system to adequately react and to physically disconnect from the system.
3. Varistor with an intentionally incorporated weak spot in the structure as claimed in Claims 1 and 2, characterized in that temperature on the location with the intentionally incorporated weak spot increases by 10 % to 40 % more quickly in case of electrical overload than on the remaining parts of the body of the varistor.
4. Varistor with an intentionally incorporated weak spot in the structure as claimed in Claims 1 and 2, characterized in that an intentionally incorporated defined weak spot (2) with a deepening (2a) is arranged on the surface of the body (1) of the varistor, that the surface of the spot (2) lies in the range from 0.05 % to 60 % of the entire surface of the body (1) of the varistor, that the deepening (2a) amounts to 0.1 to 1 mm or 0.1 % to 30 % of the entire thickness of the body (1) of the varistor.
5. Varistor with an intentionally incorporated weak spot in the structure as claimed in Claims 1 and 2, characterized in that there is a weak spot (3) of a rectangular shape with a deepening (3a) arranged on a body (1) of the varistor, that the surface of the spot (3) lies in the range from 0.05 % to 60 % of the entire surface of the varistor (1), that the deepening (3a) amounts to 0.1 to 1 mm or 0.1 % to 30 % of the thickness of the body (1 ) of the varistor.
6. Varistor with an intentionally incorporated weak spot in the structure as claimed in Claim 1 , characterized in that the intentionally incorporated weak spot (4) in the deepening of the body (1) of the varistor is formed by inserting substances of organic or inorganic origin that cause an effect of local heating as claimed in Claim 3.
7. Varistor with an intentionally incorporated weak spot in the structure as claimed in any Claims from 1 to 6, characterized in that there is an optional number of intentionally incorporated weak spots.
8. Varistor with an intentionally incorporated weak spot in the structure as claimed in any Claims from 1 to 6, characterized in that the intentionally incorporated weak spot is of an optional geometrical shape. Varistor with an intentionally incorporated weak spot in the structure as claimed in any Claims from 1 to 8, characterized in that the intentionally incorporated weak spots are of different geometrical shapes.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SIP-200900126 | 2009-04-29 | ||
| SI200900126A SI23040B (en) | 2009-04-29 | 2009-04-29 | Varistor with defined weak spot within its structure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2010126453A1 true WO2010126453A1 (en) | 2010-11-04 |
Family
ID=42563012
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/SI2010/000022 WO2010126453A1 (en) | 2009-04-29 | 2010-04-29 | A varistor with a defined weak spot in the structure |
Country Status (2)
| Country | Link |
|---|---|
| SI (1) | SI23040B (en) |
| WO (1) | WO2010126453A1 (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6252488B1 (en) * | 1999-09-01 | 2001-06-26 | Leviton Manufacturing Co., Inc. | Metal oxide varistors having thermal protection |
| US20040207969A1 (en) * | 2001-07-15 | 2004-10-21 | Bernd Kruska | Surge voltage protector for use in power transmission networks |
| US20040264092A1 (en) * | 2001-08-02 | 2004-12-30 | Hermann Grunbichler | Electroceramic component |
| DE102007049988A1 (en) * | 2007-10-12 | 2008-10-30 | Siemens Ag | Varistor blocks connecting method, involves connecting varistor blocks with electrically conductive intermediate layer by friction welding i.e. ultrasonic welding, at edge region of contact surface |
-
2009
- 2009-04-29 SI SI200900126A patent/SI23040B/en active Search and Examination
-
2010
- 2010-04-29 WO PCT/SI2010/000022 patent/WO2010126453A1/en active Application Filing
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6252488B1 (en) * | 1999-09-01 | 2001-06-26 | Leviton Manufacturing Co., Inc. | Metal oxide varistors having thermal protection |
| US20040207969A1 (en) * | 2001-07-15 | 2004-10-21 | Bernd Kruska | Surge voltage protector for use in power transmission networks |
| US20040264092A1 (en) * | 2001-08-02 | 2004-12-30 | Hermann Grunbichler | Electroceramic component |
| DE102007049988A1 (en) * | 2007-10-12 | 2008-10-30 | Siemens Ag | Varistor blocks connecting method, involves connecting varistor blocks with electrically conductive intermediate layer by friction welding i.e. ultrasonic welding, at edge region of contact surface |
Also Published As
| Publication number | Publication date |
|---|---|
| SI23040A (en) | 2010-10-29 |
| SI23040B (en) | 2018-06-29 |
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