WO1990000825A1 - Assemblies of ptc circuit protection devices - Google Patents

Assemblies of ptc circuit protection devices Download PDF

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Publication number
WO1990000825A1
WO1990000825A1 PCT/US1989/003074 US8903074W WO9000825A1 WO 1990000825 A1 WO1990000825 A1 WO 1990000825A1 US 8903074 W US8903074 W US 8903074W WO 9000825 A1 WO9000825 A1 WO 9000825A1
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WO
WIPO (PCT)
Prior art keywords
devices
ptc
assembly according
series
device assembly
Prior art date
Application number
PCT/US1989/003074
Other languages
French (fr)
Inventor
David A. Horsma
Hundi P. Kamath
Shou-Mean Fang
Original Assignee
Raychem Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Raychem Corporation filed Critical Raychem Corporation
Priority to EP89908919A priority Critical patent/EP0429489B1/en
Priority to KR1019900700539A priority patent/KR0178953B1/en
Priority to DE68922733T priority patent/DE68922733T2/en
Publication of WO1990000825A1 publication Critical patent/WO1990000825A1/en
Priority to HK98105930A priority patent/HK1006899A1/en

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Classifications

    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
    • H02H9/026Current limitation using PTC resistors, i.e. resistors with a large positive temperature coefficient
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H33/00High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
    • H01H33/02Details
    • H01H33/04Means for extinguishing or preventing arc between current-carrying parts
    • H01H33/16Impedances connected with contacts
    • H01H33/161Variable impedances
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H33/00High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
    • H01H33/02Details
    • H01H33/04Means for extinguishing or preventing arc between current-carrying parts
    • H01H33/16Impedances connected with contacts
    • H01H33/161Variable impedances
    • H01H2033/163Variable impedances using PTC elements

Definitions

  • This invention relates to electrical devices comprising PTC materials.
  • PTC materials whose resistivity increases sharply with temperature over a relatively small temperature range. Such materials are said to be "PTC materials” or to “exhibit PTC behavior", PTC being an abbre ⁇ viation of "positive temperature coefficient”.
  • a PTC material should exhibit an R_ value of at least 2.5 and/or an va l ue ° ⁇ - at least 10 , and particularly preferred that it should have an R30 value of at least 6 , where R_4 is the ratio of the resistivities at the end and the beginning of a 14°C range, R]_00 is the ra tio of the resistivities at the end and the beginning of a 100°C range, and R30 is the ratio of the resistivities at the end and the beginning of a 30°C range.
  • a plot of the log of the resistance of a PTC element (i.e. an element composed of a PTC composition) against temperature will often show a sharp change in slope over a part of the temperature range in which the composition has an R_oo v l ue of at least 10.
  • switching temperature (usually abbreviated T s ) is used herein to denote the temperature at the intersection point of extensions of the substantially straight portions of such a plot which lie either side of the portion showing the sharp change in slope.
  • peak resistivity is used herein to denote the maximum resistivity which the composition exhibits above T s
  • peak temperature is used to denote the temperature at which the composition has its peak resistivity.
  • PTC elements have proved particularly useful as com ⁇ ponents of self-regulating heaters and of circuit protection devices.
  • the PTC materials which have been used or proposed for use in such electrical devices are certain ceramics and certain conductive polymers, the term "conductive polymer” being used herein to denote a composition which comprises an organic polymer (this term being used to include poly- siloxanes) and, dispersed or otherwise distributed in the organic polymer, a particulate conductive filler.
  • Suitable ceramic materials include doped barium titanates, and suitable conductive polymers include crystalline polymers having carbon black dispersed therein.
  • PTC ceramics generally exhibit a sharp change in resistivity at the Curie point of the material, and PTC conductive polymers generally exhibit a sharp change in resistivity over a temperature range just below the crystalline melting point of the poly ⁇ meric matrix.
  • the PTC ceramics which are used in commercial practice generally show a sharper rate of increase in resistivity than do the PTC conductive polymers.
  • PTC ceramics generally have a resistivity of at least 30 ohm-cm at 23°C, whereas PTC conductive polymers can have a lower resistivity at 23°C, e.g. down to about 1 ohm-cm or lower.
  • PTC ceramics tend to crack and thus to fail suddenly if exposed to excessive electrical stress, whereas PTC conductive polymers tend to degrade relatively slowly.
  • hold current (or "pass current”) is used to denote the maximum steady current which can be passed through a PTC circuit protection device without causing it to trip (i.e. be converted into a high temperature, high resistance state such that the circuit current is reduced to a very low level).
  • the hold current of a device depends upon the rate at which heat is lost from the device; for example, the higher the ambient temperature, the higher the hold current. It is known to connect a plurality of substantially identical devices in parallel to provide a PTC protection assembly having a hold current which is sub ⁇ stantially equal to the sum of the hold currents of the individual devices.
  • the performance characteristics of a PTC circuit protection device depend importantly on the voltage which is dropped across it in the tripped state; the higher the voltage, the.
  • Another unsolved problem is the provision of devices which will protect against voltages that can be handled by existing devices, but which are easier to manufacture than existing devices (e.g. require less or no crosslinking) and/or which have a more convenient shape (the shape often being largely determined by the configuration and separation of the electrodes), either for installation or in use (e.g. on a printed circuit board or in other situations where space is at a premium) and/or for thermal balance considerations.
  • the device assembly can be used on its own, if it will withstand the electrical stress exerted on it when a fault condition occurs.
  • the assembly can be used in conjunction with a circuit breaker.
  • the device assembly holds and controls the excessive current for a period of time which is short but which nevertheless substantially reduces the electrical stress on the circuit breaker, whose cost and complexity can, therefore, be substantially reduced.
  • switching apparatus which incorporates a device assembly comprising a plurality of PTC protection devices connected in series.
  • the device assembly is preferably connected in series between the terminals (which are being separated or engaged) during the switching operation but is disconnected when the switch is fully open and is disconnected or con ⁇ nected in parallel when the switch is fully closed. In this way, the device assembly controls the current during the critical period while the terminals are being separated or engaged, and reduces the danger that an arc will be struck between the terminals.
  • Figure 1 is a circuit diagram of the use of the invention for circuit protection.
  • FIGS. 2A, 2B and 2C are diagrammatic representations of successive stages of operation of a switch making use of the invention as the switch is opened.
  • Figures 3 and 4 are cross-sections of composite device assemblies of the invention.
  • Figure 5 is a plan view of another composite device assembly of the invention, and Figure 6 is a cross-section on line 6-6 of Figure 5.
  • the number of protection devices which are connected in series is generally at least three, preferably at least five, and can be many more, e.g. up to 100.
  • the devices will often all be devices which have been made by the same manufacturing process. However, this is not necessary.
  • the number of devices connected in series will be B/A.
  • the rating is generally a conservative one, a number of devices which is less than B/A can be used, particularly when a large number of devices are employed.
  • a device assembly for protecting a 6KV 600 amp circuit might comprise 600 sets, connected in parallel, each set being made up of ten 600 volt 1 amp protection devices.
  • the device assembly can be operated under adiabatic conditions, or can be such that heat is transferred between the devices during the tripping operation.
  • the devices can be separated from each other, e.g. by an inert insulating liquid, or (particularly when laminar devices are employed) can be stacked one on top of the other or secured to a thermally conductive substrate.
  • Figure 1 is a circuit diagram in which a device assembly 1 is connected in series with a circuit breaker 12, a switch 13, a source of power 14 and a load RL.
  • Figure 2 shows the sequential opening of a switch which comprises a stationary portion 21 and a slidable portion 22. Electrical connection from the device assembly 1 is made through stationary terminal 23.
  • switch When the switch is closed ( Figure 2A) , terminal 23 is in physical contact with slidable portion 22.
  • a specific event e.g. a voltage surge
  • the contact is broken between the portions of the switch, and slidable portion 22 moves away from stationary portion 21 ( Figure 2B) .
  • the switch is completely open, the terminal 23 is physically separated from the slidable portion 22 of the switch ( Figure 2C) .
  • Figures 3 and 4 show cross-sectional views of composite device assemblies 30 of the invention.
  • Each assembly shown comprises three devices 31 which are adjacent to, and electrically in series with, one another.
  • the devices comprise a PTC element 32 and two electrodes 33, although in some embodiments in which the devices are in physical and thermal contact, some or all of the devices need have only a single electrode.
  • Electrical leads 34 are attached to the opposite faces of the assembly stack in order to make electrical connection to a power supply or circuit.
  • the assembly of Figure 3 comprises devices of the same size, although, as shown in Figure 4, devices of different sizes and/or comprising compositions of different resistivities may be used.
  • Figure 5 is a plan view of a composite device assembly 50.
  • a substrate 51 which comprises a PTC composition is laminated, printed, or otherwise supplied with metal electrode strips 52. Slots 53 may be machined or etched through the thickness of the PTC substrate and lead wire 54 may be attached to individual devices 55 in order to produce the desired series/parallel configuration.
  • Figure 6 shows a cross-sectional view on line 6-6 of Figure 5 in which the PTC substrate 51 comprises a conductive polymer.
  • a conductive polymer composition was prepared by mixing the following ingredients (by volume) in a Banbury mixer: 56.7% high density polyethylene (MarlexTM 6003, available from Phillips Petroleum), 25.1% carbon black (SterlingTM SO, available from Cabot), 16.5% silane-coated alumina tri- hydrate (SolemTM 916SP, available from J. M. Huber) , and 1.7% antioxidant (an oligomer of 4,4-thio bis(3-methyl 1-6-t-butyl phenol) as described in U.S. Patent No. 3,-986,981).
  • Banbury mixer 56.7% high density polyethylene (MarlexTM 6003, available from Phillips Petroleum), 25.1% carbon black (SterlingTM SO, available from Cabot), 16.5% silane-coated alumina tri- hydrate (SolemTM 916SP, available from J. M. Huber) , and 1.7% antioxidant (an oligomer of 4,4-thio bis(3-methyl 1-6-t-butyl phenol) as described in
  • pellets of the composition were melt-extruded around two 20 AWG 19/32 nickel-coated copper wires which had been coated with a graphite/silicate com ⁇ position (Electrodag 1 * 181, available from Acheson Colloids).
  • the extrudate was cut into pieces, and the conductive polymer was removed from part of the device to expose the electrodes.
  • the devices were heat-treated at 150°C in nitrogen for one hour, irradiated with a 1.5 MeV electron beam to a dose of 20 Mrad, heat-treated a second time, irradiated to a dose of 150 Mrad, and heat-treated a third ti e. After processing, the devices had a resistance of 16.5 to 18.5 ohms and had maximum voltage and current ratings of 600 volts and 1 amp, respectively.
  • Ten devices were electrically connected in series and were then inserted into a beaker which was filled with a thermally dissipating liquid (Fluorinert ,M FC-75, available from DuPont) .
  • the beaker was placed in a water bath heated to 100°C and the devices were allowed to equilibrate to the temperature.
  • the devices were connected to a series ballast resistance of 500 ohms and were then powered at 6000 volts/2 amps r s for a period of 0.4 seconds.
  • the voltage and current were monitored with an oscilloscope during the test, and the resistance of each device was measured at the start and conclusion of the test.
  • the oscilloscope traces indi ⁇ cated that the devices which tripped did so within three AC cycles.
  • a conductive polymer composition with a resistivity of about 4 ohm-cm was prepared by mixing 56.1 vol% high density polyethylene (MarlexTM HXM 50100, available from Phillips Petroleum), 26.7 vol% carbon black (StatexTM G, available from Columbian Chemicals), 15.5 vol% magnesium hydroxide (Kisuma" * 5A, available from Kisuma), and 1.7 vol% antioxidant (as
  • Example 1 Pellets of the composition were extruded to produce a sheet with a thickness of 0.040 inch (0.10 cm). After laminating the sheet on each side with electrodeposited nickel foil electrodes (available from Fukuda), the sheet was irradiated to a dose of 10 Mrad. Devices with a diameter of 0.360 inch (0.914 cm) and a resistance of 0.66 ohms were cut from the plaque. Each device was nominally capable of withstanding 60 volt/40 amp electrical powering. Three devices were stacked together and two metal leads were soldered to the top and bottom surfaces of the stack.
  • Example 4 Five devices as described in Example 2 were stacked to produce a composite device assembly with a resistance of 3.94 ohms. When tested at 600 volts/1 amp, the composite device assembly survived 17 seconds before tripping. When tested at 300 volts/1 amp, the composite device assembly survived 145 cycles.
  • Example 4 Five devices as described in Example 2 were stacked to produce a composite device assembly with a resistance of 3.94 ohms. When tested at 600 volts/1 amp, the composite device assembly survived 17 seconds before tripping. When tested at 300 volts/1 amp, the composite device assembly survived 145 cycles. Example 4
  • a conductive polymer composition with a resistivity of about 1 ohm-cm was prepared by mixing 65.8 vol% high density polyethylene (MarlexTM 6003, available from Phillips Petroleum) with 34.2 vol% carbon black (RavenTM 600, available from Columbian Chemicals) in a Banbury mixer. The composition was extruded, laminated with metal foil, and irradiated as described in Example 2. Two devices with a diameter of 0.360 inch (0.91 cm) and a resistance of 0.148 ohm were cut from the laminated sheet. Using the procedure of Example 2, these devices were positioned on either side of a device as described in Example 2 to produce a composite device assembly with a resistance of 1.185 ohms. When tested at 600 volts/1 amp, the composite device assembly survived 45 seconds before tripping. At 300 volts/1 amp (power applied for 40 seconds), the composite device assemblies survived 145 cycles.
  • Example 2 A device as described in Example 2 (diameter 0.360 inch) was sandwiched between two devices with a diameter of 0.250 inch (0.64 cm) cut from the sheet described in Example 4 to produce a composite device assembly with a resistance of 2.1 ohms. When powered at 600 volts/1 amp, the composite device assembly tripped in 11 seconds. At 300 volts/ 1 amp/40 sec, the composite device assemblies survived 20 to 120 cycles.

Abstract

A device assembly (1) in which a plurality of PTC circuit protection devices (31) are connected in series. Assemblies of this type are useful in providing protection under voltage conditions which would be unsafe for an individual protection device. In a preferred system the device assembly (1) is connected in series with a circuit breaker (12).

Description

ASSEMBLIES OF PTC CIRCUIT PROTECTION DEVICES
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to electrical devices comprising PTC materials.
Background of the Invention
There are a number of known materials whose resistivity increases sharply with temperature over a relatively small temperature range. Such materials are said to be "PTC materials" or to "exhibit PTC behavior", PTC being an abbre¬ viation of "positive temperature coefficient". For many purposes, it is preferred that a PTC material should exhibit an R_ value of at least 2.5 and/or an
Figure imgf000003_0001
value °~- at least 10 , and particularly preferred that it should have an R30 value of at least 6 , where R_4 is the ratio of the resistivities at the end and the beginning of a 14°C range, R]_00 is the ratio of the resistivities at the end and the beginning of a 100°C range, and R30 is the ratio of the resistivities at the end and the beginning of a 30°C range. Many PTC materials show increases in resistivity which are very much greater than these minimum values. A plot of the log of the resistance of a PTC element (i.e. an element composed of a PTC composition) against temperature will often show a sharp change in slope over a part of the temperature range in which the composition has an R_oo v lue of at least 10. The term "switching temperature" (usually abbreviated Ts) is used herein to denote the temperature at the intersection point of extensions of the substantially straight portions of such a plot which lie either side of the portion showing the sharp change in slope. The term "peak resistivity" is used herein to denote the maximum resistivity which the composition exhibits above Ts, and the term "peak temperature" is used to denote the temperature at which the composition has its peak resistivity.
PTC elements have proved particularly useful as com¬ ponents of self-regulating heaters and of circuit protection devices. The PTC materials which have been used or proposed for use in such electrical devices are certain ceramics and certain conductive polymers, the term "conductive polymer" being used herein to denote a composition which comprises an organic polymer (this term being used to include poly- siloxanes) and, dispersed or otherwise distributed in the organic polymer, a particulate conductive filler. Suitable ceramic materials include doped barium titanates, and suitable conductive polymers include crystalline polymers having carbon black dispersed therein. PTC ceramics generally exhibit a sharp change in resistivity at the Curie point of the material, and PTC conductive polymers generally exhibit a sharp change in resistivity over a temperature range just below the crystalline melting point of the poly¬ meric matrix. The PTC ceramics which are used in commercial practice generally show a sharper rate of increase in resistivity than do the PTC conductive polymers. PTC ceramics generally have a resistivity of at least 30 ohm-cm at 23°C, whereas PTC conductive polymers can have a lower resistivity at 23°C, e.g. down to about 1 ohm-cm or lower. PTC ceramics tend to crack and thus to fail suddenly if exposed to excessive electrical stress, whereas PTC conductive polymers tend to degrade relatively slowly.
Documents which disclose circuit protection devices comprising PTC conductive polymers include U.S. Patent Nos. 4,237,441, 4,239,812, 4,255,698, 4,315,237, 4,317,027, 4,329,726, 4,352,083, 4,475,138, 4,481,498, 4,639,818, 4,647,894, 4,645,896, 4,685,025, 4,689,475, 4,724,417, and 4,774,024; European Publication No. 38,713 (published September 2, 1987); International Publication No. WO89/03162 (published April 6, 1989); and the trade pamphlets published by Raychem Corporation in January 1987 and entitled "A General Approach to Circuit Design with PolySwitch Devices", "Protection of Subscriber Line Interface Circuits with PolySwitch Devices", "Protection of PBX and Key Telephone Systems with PolySwitch Devices", "Protection of Telecommunications Networks with PolySwitch Devices", "Protection of Loudspeakers with PolySwitch Devices", and "Protection of Batteries with PolySwitch Devices". ("PolySwitch" is a registered trademark of Raychem Corporation. )
The term "hold current" (or "pass current") is used to denote the maximum steady current which can be passed through a PTC circuit protection device without causing it to trip (i.e. be converted into a high temperature, high resistance state such that the circuit current is reduced to a very low level). The hold current of a device depends upon the rate at which heat is lost from the device; for example, the higher the ambient temperature, the higher the hold current. It is known to connect a plurality of substantially identical devices in parallel to provide a PTC protection assembly having a hold current which is sub¬ stantially equal to the sum of the hold currents of the individual devices. The performance characteristics of a PTC circuit protection device depend importantly on the voltage which is dropped across it in the tripped state; the higher the voltage, the. greater the danger that the device will be damaged and will thus fail to provide the desired protection and/or will fail in a hazardous way, e.g. will explode or burn. As is apparent from the patents and appli¬ cations incorporated herein by reference, much effort has been devoted to increasing the voltage which can safely be dropped over PTC conductive polymer circuit protection devices. In general, the greater the distance between the electrodes, and the greater the extent of the crosslinking of the conductive polymer, the higher the voltage which can be employed. While there are available protection devices which can safely handle a voltage of about 600 volts RMS, protection against higher voltages remains a problem. Another unsolved problem is the provision of devices which will protect against voltages that can be handled by existing devices, but which are easier to manufacture than existing devices (e.g. require less or no crosslinking) and/or which have a more convenient shape (the shape often being largely determined by the configuration and separation of the electrodes), either for installation or in use (e.g. on a printed circuit board or in other situations where space is at a premium) and/or for thermal balance considerations.
SUMMARY OF THE INVENTION
As noted above, it is known to connect a plurality of substantially identical PTC protection devices in parallel in order to provide a protection assembly having a hold current substantially equal to the sum of the hold currents of the'individual devices. It is not known, however, to connect a plurality of PTC protection devices in series in order to provide an assembly which can safely handle a voltage higher than can be handled by any of the devices individually. The reason for this is as follows. Theoretical considerations make it clear that this desirable result should be achieved by a plurality of series-connected devices which are precisely identical and which are in precisely identical thermal environments. However, those skilled in the art have held the belief that this desirable result would never in fact be achieved because it is not in practice possible to make devices which are precisely identical or to place them in precisely identical thermal environments, and because even the smallest difference, under fault conditions, would cause a single one of the devices to increase in resistance much more rapidly than the others and thus to shoulder the whole of the voltage burden. Consequently, those skilled in the art have believed that the ability of a number of devices, connected in series, to control excessive current is no greater than the ability of the single device which trips.
We have discovered that there are many circumstances in which this belief is not justified. In particular, we have discovered that if due account is taken of the dynamic variables during the tripping process (e.g. the rate of change of the current, the rate of change of resistivity with temperature, and the rate at which heat is removed from the devices, including in some cases transfer of heat between devices), the electrical stress can be shared between the devices. In some cases, the sharing of the electrical stress will last only for a limited time, and maintenance of the fault condition which caused tripping will result in substantially all of the electrical stress being concentrated on a single device. In some such cases, this is a satisfactory outcome because the single device, having been converted into the tripped condition over a substantially longer time period because of the temporary sharing of the electrical stress, can safely handle the voltage which is being dropped over it in the steady state condition. In other such cases, this is not true, but the time during which electrical stress is shared is neverthe¬ less highly significant because it is long enough to allow another desired change (e.g. the making or breaking of a contact) to take place under conditions which are substan¬ tially less severe than they would otherwise be, for example if only one or a lesser number of protection devices had been present. Providing such other change (a) takes place before there is an excessive electrical stress on the device which is bearing the greatest share of the stress and (b) interrupts the circuit (or otherwise prevents the exertion of excessive stress on that device, then the series of devices will safely handle a substantially higher voltage than any one of the devices alone. In other cases, the electrical stress is also shared in the steady state con¬ dition, with more than one of the protection devices being in a tripped condition; in some cases one or more of the tripped devices is also in a latched condition (i.e. the device remains in the high resistance state even if the fault condition is removed, unless power is removed from the circuit) .
One very valuable use of this discovery is in circuit protection applications wherein a plurality of PTC protec¬ tion devices are connected in series to form a device assembly. The device assembly can be used on its own, if it will withstand the electrical stress exerted on it when a fault condition occurs. Alternatively, the assembly can be used in conjunction with a circuit breaker. In the latter embodiment, the device assembly holds and controls the excessive current for a period of time which is short but which nevertheless substantially reduces the electrical stress on the circuit breaker, whose cost and complexity can, therefore, be substantially reduced.
Another very valuable use of this discovery is in switching apparatus which incorporates a device assembly comprising a plurality of PTC protection devices connected in series. The device assembly is preferably connected in series between the terminals (which are being separated or engaged) during the switching operation but is disconnected when the switch is fully open and is disconnected or con¬ nected in parallel when the switch is fully closed. In this way, the device assembly controls the current during the critical period while the terminals are being separated or engaged, and reduces the danger that an arc will be struck between the terminals.
BRIEF DESCRIPTION OF THE DRAWING
The invention is illustrated in the accompanying drawing, in which
Figure 1 is a circuit diagram of the use of the invention for circuit protection.
Figures 2A, 2B and 2C are diagrammatic representations of successive stages of operation of a switch making use of the invention as the switch is opened.
Figures 3 and 4 are cross-sections of composite device assemblies of the invention.
Figure 5 is a plan view of another composite device assembly of the invention, and Figure 6 is a cross-section on line 6-6 of Figure 5.
DETAILED DESCRIPTION OF THE INVENTION *
The number of protection devices which are connected in series is generally at least three, preferably at least five, and can be many more, e.g. up to 100. The devices will often all be devices which have been made by the same manufacturing process. However, this is not necessary. In general, when using devices which have been rated for use up to a particular voltage (A volts), and the voltage across the assembly in the fault condition is B volts, the number of devices connected in series will be B/A. However, since the rating is generally a conservative one, a number of devices which is less than B/A can be used, particularly when a large number of devices are employed. It is of course important to ensure also that the hold current of the device assembly is sufficiently high, and for this purpose a plurality of sets of devices in series can be placed in parallel with each other. For example a device assembly for protecting a 6KV 600 amp circuit might comprise 600 sets, connected in parallel, each set being made up of ten 600 volt 1 amp protection devices.
The device assembly can be operated under adiabatic conditions, or can be such that heat is transferred between the devices during the tripping operation. For example, the devices can be separated from each other, e.g. by an inert insulating liquid, or (particularly when laminar devices are employed) can be stacked one on top of the other or secured to a thermally conductive substrate.
The invention is illustrated in the drawing in which Figure 1 is a circuit diagram in which a device assembly 1 is connected in series with a circuit breaker 12, a switch 13, a source of power 14 and a load RL.
Figure 2 shows the sequential opening of a switch which comprises a stationary portion 21 and a slidable portion 22. Electrical connection from the device assembly 1 is made through stationary terminal 23. When the switch is closed (Figure 2A) , terminal 23 is in physical contact with slidable portion 22. When a specific event (e.g. a voltage surge) occurs, the contact is broken between the portions of the switch, and slidable portion 22 moves away from stationary portion 21 (Figure 2B) . When the switch is completely open, the terminal 23 is physically separated from the slidable portion 22 of the switch (Figure 2C) .
Figures 3 and 4 show cross-sectional views of composite device assemblies 30 of the invention. Each assembly shown comprises three devices 31 which are adjacent to, and electrically in series with, one another. The devices comprise a PTC element 32 and two electrodes 33, although in some embodiments in which the devices are in physical and thermal contact, some or all of the devices need have only a single electrode. Electrical leads 34 are attached to the opposite faces of the assembly stack in order to make electrical connection to a power supply or circuit. The assembly of Figure 3 comprises devices of the same size, although, as shown in Figure 4, devices of different sizes and/or comprising compositions of different resistivities may be used.
Figure 5 is a plan view of a composite device assembly 50. A substrate 51 which comprises a PTC composition is laminated, printed, or otherwise supplied with metal electrode strips 52. Slots 53 may be machined or etched through the thickness of the PTC substrate and lead wire 54 may be attached to individual devices 55 in order to produce the desired series/parallel configuration.
Figure 6 shows a cross-sectional view on line 6-6 of Figure 5 in which the PTC substrate 51 comprises a conductive polymer.
EXAMPLES
The invention is illustrated by the following examples.
Example 1
A conductive polymer composition was prepared by mixing the following ingredients (by volume) in a Banbury mixer: 56.7% high density polyethylene (Marlex™ 6003, available from Phillips Petroleum), 25.1% carbon black (Sterling™ SO, available from Cabot), 16.5% silane-coated alumina tri- hydrate (Solem™ 916SP, available from J. M. Huber) , and 1.7% antioxidant (an oligomer of 4,4-thio bis(3-methyl 1-6-t-butyl phenol) as described in U.S. Patent No. 3,-986,981). Using a Brabender crosshead extruder fitted with, a dogbone-shaped die, pellets of the composition were melt-extruded around two 20 AWG 19/32 nickel-coated copper wires which had been coated with a graphite/silicate com¬ position (Electrodag1* 181, available from Acheson Colloids). The extrudate was cut into pieces, and the conductive polymer was removed from part of the device to expose the electrodes. The devices were heat-treated at 150°C in nitrogen for one hour, irradiated with a 1.5 MeV electron beam to a dose of 20 Mrad, heat-treated a second time, irradiated to a dose of 150 Mrad, and heat-treated a third ti e. After processing, the devices had a resistance of 16.5 to 18.5 ohms and had maximum voltage and current ratings of 600 volts and 1 amp, respectively.
Ten devices were electrically connected in series and were then inserted into a beaker which was filled with a thermally dissipating liquid (Fluorinert,M FC-75, available from DuPont) . The beaker was placed in a water bath heated to 100°C and the devices were allowed to equilibrate to the temperature. The devices were connected to a series ballast resistance of 500 ohms and were then powered at 6000 volts/2 amps r s for a period of 0.4 seconds. The voltage and current were monitored with an oscilloscope during the test, and the resistance of each device was measured at the start and conclusion of the test. The oscilloscope traces indi¬ cated that the devices which tripped did so within three AC cycles.
The resistances for three different experimental groups of ten devices are listed in Table I. Those devices which did not trip during the test are indicated by an asterisk (*). When the ratio of resistance after the test (Rf) to initial resistance (R_) was greater than 1.2, the device was deemed to have tripped; those between 1.10 and 1.19 did not completely trip. During each test, 50 to 70% of the devices tripped.
Example 2
A conductive polymer composition with a resistivity of about 4 ohm-cm was prepared by mixing 56.1 vol% high density polyethylene (Marlex™ HXM 50100, available from Phillips Petroleum), 26.7 vol% carbon black (Statex™ G, available from Columbian Chemicals), 15.5 vol% magnesium hydroxide (Kisuma"* 5A, available from Kisuma), and 1.7 vol% antioxidant (as
Figure imgf000014_0001
described in Example 1) in a Banbury mixer. Pellets of the composition were extruded to produce a sheet with a thickness of 0.040 inch (0.10 cm). After laminating the sheet on each side with electrodeposited nickel foil electrodes (available from Fukuda), the sheet was irradiated to a dose of 10 Mrad. Devices with a diameter of 0.360 inch (0.914 cm) and a resistance of 0.66 ohms were cut from the plaque. Each device was nominally capable of withstanding 60 volt/40 amp electrical powering. Three devices were stacked together and two metal leads were soldered to the top and bottom surfaces of the stack. During the lead attachment process, solder stuck to the exposed edges of the electrodes of each of the three devices, fusing the devices' together to give a composite device assembly with a resistance of 2.56 ohms. When tested under 600 volt/1 amp impulse conditions, the composite device assembly survived 12 to 18 seconds before failing. When tested at 300 volts/1 amp, the composite device assembly tripped in less than 17 seconds and survived 132 test cycles. Under conventional testing, the individual devices comprising the composite device assembly would not survive voltage impulses of 300 to 600 volts.
Example 3
Five devices as described in Example 2 were stacked to produce a composite device assembly with a resistance of 3.94 ohms. When tested at 600 volts/1 amp, the composite device assembly survived 17 seconds before tripping. When tested at 300 volts/1 amp, the composite device assembly survived 145 cycles. Example 4
A conductive polymer composition with a resistivity of about 1 ohm-cm was prepared by mixing 65.8 vol% high density polyethylene (Marlex™ 6003, available from Phillips Petroleum) with 34.2 vol% carbon black (Raven™ 600, available from Columbian Chemicals) in a Banbury mixer. The composition was extruded, laminated with metal foil, and irradiated as described in Example 2. Two devices with a diameter of 0.360 inch (0.91 cm) and a resistance of 0.148 ohm were cut from the laminated sheet. Using the procedure of Example 2, these devices were positioned on either side of a device as described in Example 2 to produce a composite device assembly with a resistance of 1.185 ohms. When tested at 600 volts/1 amp, the composite device assembly survived 45 seconds before tripping. At 300 volts/1 amp (power applied for 40 seconds), the composite device assemblies survived 145 cycles.
Example 5
A device as described in Example 2 (diameter 0.360 inch) was sandwiched between two devices with a diameter of 0.250 inch (0.64 cm) cut from the sheet described in Example 4 to produce a composite device assembly with a resistance of 2.1 ohms. When powered at 600 volts/1 amp, the composite device assembly tripped in 11 seconds. At 300 volts/ 1 amp/40 sec, the composite device assemblies survived 20 to 120 cycles.

Claims

1. A device assembly which comprises a plurality of PTC circuit protection devices connected in series.
2. An assembly according to Claim 1 which comprises at least three devices connected in series.
3. An assembly according to Claim 1 or 2 which comprises at least three laminar PTC elements, each of said PTC elements being sandwiched between two laminar metal electrodes, and the PTC elements being stacked on top of each other but separated by laminar metal electrodes.
4. An assembly according to any one of the preceding claims wherein the devices have all been manufactured by the same manufacturing process.
5. An assembly according to any one of the preceding claims which comprises a plurality of sets of devices connected in series, the sets being connected in parallel with each other.
6. An assembly according to any one of the preceding claims wherein each of the devices comprises a PTC element composed of a conductive polymer.
7. An assembly according to Claim 1, 3 or 5 wherein each of the devices comprises a PTC element composed of a ceramic.
8. An assembly according to any one of the preceding claims wherein the devices are immersed in an insulating liquid.
9. An electrical circuit breaking system which comprises (1) a circuit breaker, and
(2) a device assembly according to any one of the preceding claims which is connected in series with the circuit breaker.
10. An electrical switching system which has a closed configuration, an intermediate configuration, and an open configuration, and which comprises
(1) a first metal contact surface,
(2) a second metal contact surface, and
(3) a device assembly according any one of the preceding claims
wherein the first and second surfaces are in direct physical contact when the system is in the closed configuration; the first and second surfaces being physically separated from each other but electrically connected to each other through the device assembly when the system is in the intermediate configuration; and the first and second surfaces being physically and electrically separated from each other when the system is in the open configuration.
PCT/US1989/003074 1988-07-15 1989-07-14 Assemblies of ptc circuit protection devices WO1990000825A1 (en)

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EP89908919A EP0429489B1 (en) 1988-07-15 1989-07-14 Assemblies of ptc circuit protection devices
KR1019900700539A KR0178953B1 (en) 1988-07-15 1989-07-14 Assemblies of ptc circuit protection device
DE68922733T DE68922733T2 (en) 1988-07-15 1989-07-14 PTC CIRCUIT PROTECTION ARRANGEMENTS.
HK98105930A HK1006899A1 (en) 1988-07-15 1998-06-22 Assemblies of ptc circuit protection devices

Applications Claiming Priority (2)

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US219,416 1980-12-22
US07/219,416 US4967176A (en) 1988-07-15 1988-07-15 Assemblies of PTC circuit protection devices

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4340632A1 (en) * 1993-11-30 1995-06-01 Abb Patent Gmbh Electrical switching device
FR2716754A1 (en) * 1994-01-31 1995-09-01 Gen Electric Current limiter with calibration module.
EP0749140A1 (en) * 1995-06-13 1996-12-18 Gec Alsthom T Et D Sa Interruption device for high-tension DC
EP0780849A2 (en) 1995-12-23 1997-06-25 Abb Research Ltd. Process of manufacturing a PTC resistor material
US5644283A (en) * 1992-08-26 1997-07-01 Siemens Aktiengesellschaft Variable high-current resistor, especially for use as protective element in power switching applications & circuit making use of high-current resistor
DE19702094A1 (en) * 1997-01-22 1998-07-23 Abb Research Ltd Circuit breaker

Families Citing this family (52)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3203803B2 (en) * 1992-09-01 2001-08-27 株式会社デンソー Thermistor type temperature sensor
US5379176A (en) * 1993-05-03 1995-01-03 John Fluke Mfg. Co., Inc. Protective input circuit for an instrument
CA2143711A1 (en) * 1994-12-30 1996-07-01 Craig A. Miller High voltage d-c current limiter
US5668521A (en) * 1995-03-22 1997-09-16 Littelfuse, Inc. Three piece female blade fuse assembly having fuse link terminal with a clip receiving portion
ES2182971T3 (en) * 1995-05-04 2003-03-16 Aventis Pasteur ACCELULAR PERTUSSIS VACCINES AND METHODS OF PREPARATION OF THE SAME.
US5945903A (en) * 1995-06-07 1999-08-31 Littelfuse, Inc. Resettable automotive circuit protection device with female terminals and PTC element
US5663861A (en) * 1995-06-07 1997-09-02 Littelfuse, Inc. Resettable automotive circuit protection device
WO1997006660A2 (en) * 1995-08-15 1997-02-27 Bourns, Multifuse (Hong Kong), Ltd. Surface mount conductive polymer devices and method for manufacturing such devices
TW309619B (en) * 1995-08-15 1997-07-01 Mourns Multifuse Hong Kong Ltd
US5864458A (en) * 1995-09-14 1999-01-26 Raychem Corporation Overcurrent protection circuits comprising combinations of PTC devices and switches
US5737160A (en) * 1995-09-14 1998-04-07 Raychem Corporation Electrical switches comprising arrangement of mechanical switches and PCT device
US5666254A (en) * 1995-09-14 1997-09-09 Raychem Corporation Voltage sensing overcurrent protection circuit
US5689395A (en) * 1995-09-14 1997-11-18 Raychem Corporation Overcurrent protection circuit
US6059997A (en) * 1995-09-29 2000-05-09 Littlelfuse, Inc. Polymeric PTC compositions
US5907272A (en) * 1996-01-22 1999-05-25 Littelfuse, Inc. Surface mountable electrical device comprising a PTC element and a fusible link
FR2748166B1 (en) * 1996-04-26 1998-06-05 Gec Alsthom T & D Sa HIGH VOLTAGE POLYMER CURRENT LIMITER
US6023403A (en) * 1996-05-03 2000-02-08 Littlefuse, Inc. Surface mountable electrical device comprising a PTC and fusible element
DE69739666D1 (en) 1996-07-16 2009-12-31 Ewd L L C PROTECTION CIRCUITS
FR2761204B1 (en) * 1997-03-24 1999-05-14 Siemens Automotive Sa DEVICE FOR DISTRIBUTING ELECTRICAL ENERGY IN MULTIPLE PARALLEL-POWERED CIRCUITS, AND METHOD FOR MANUFACTURING THE DEVICE
DE19882444T1 (en) 1997-06-04 2000-06-15 Tyco Electronics Corp Circuit protection devices
US5796569A (en) * 1997-06-19 1998-08-18 Yazaki Corporation Cylindrical PTC circuit overcurrent protection device
US5805393A (en) * 1997-08-29 1998-09-08 Raychem Corporation Overcurrent protection circuit with improved PTC trip endurance
US6020808A (en) * 1997-09-03 2000-02-01 Bourns Multifuse (Hong Kong) Ltd. Multilayer conductive polymer positive temperature coefficent device
US6078160A (en) * 1997-10-31 2000-06-20 Cilluffo; Anthony Bidirectional DC motor control circuit including overcurrent protection PTC device and relay
AU2492999A (en) 1998-02-06 1999-08-23 Raychem Limited Electrical protection systems
CN1201456C (en) * 1998-02-06 2005-05-11 泰科电子有限公司 Electrical systems
US6282072B1 (en) 1998-02-24 2001-08-28 Littelfuse, Inc. Electrical devices having a polymer PTC array
US6236302B1 (en) 1998-03-05 2001-05-22 Bourns, Inc. Multilayer conductive polymer device and method of manufacturing same
US6172591B1 (en) 1998-03-05 2001-01-09 Bourns, Inc. Multilayer conductive polymer device and method of manufacturing same
US6242997B1 (en) 1998-03-05 2001-06-05 Bourns, Inc. Conductive polymer device and method of manufacturing same
AU2961999A (en) 1998-04-07 1999-10-25 Tyco Electronics Reychem K.K. Secondary cell, temperature detector of secondary cell and method of manufacturing temperature detector
US6349022B1 (en) 1998-09-18 2002-02-19 Tyco Electronics Corporation Latching protection circuit
JP2002526911A (en) 1998-09-25 2002-08-20 ブアンズ・インコーポレイテッド A two-stage method for producing positive temperature coefficient polymeric materials
US6582647B1 (en) 1998-10-01 2003-06-24 Littelfuse, Inc. Method for heat treating PTC devices
US5963121A (en) * 1998-11-11 1999-10-05 Ferro Corporation Resettable fuse
US6278596B1 (en) 1999-06-17 2001-08-21 Tektronix, Inc. Active ground fault disconnect
US6300859B1 (en) 1999-08-24 2001-10-09 Tyco Electronics Corporation Circuit protection devices
US6640420B1 (en) * 1999-09-14 2003-11-04 Tyco Electronics Corporation Process for manufacturing a composite polymeric circuit protection device
US6429533B1 (en) 1999-11-23 2002-08-06 Bourns Inc. Conductive polymer device and method of manufacturing same
US6911652B2 (en) * 2000-03-22 2005-06-28 Jonathan A. Walkenstein Low light imaging device
EP1168560A3 (en) * 2000-06-19 2005-12-21 Haldor Topsoe A/S High electrical power current limiter being useful in electrical power system
US6628498B2 (en) 2000-08-28 2003-09-30 Steven J. Whitney Integrated electrostatic discharge and overcurrent device
US6853527B2 (en) * 2001-11-01 2005-02-08 Polytronics Technology Corporation Over-current protection apparatus for high voltage
TW529846U (en) * 2001-11-12 2003-04-21 Polytronics Technology Corp Over-current protection component and the device
US7050283B2 (en) * 2002-04-29 2006-05-23 Won-Door Corporation Method and apparatus for protecting monitor circuit from fault condition
US7119655B2 (en) * 2004-11-29 2006-10-10 Therm-O-Disc, Incorporated PTC circuit protector having parallel areas of effective resistance
DE102005008313A1 (en) * 2005-02-17 2006-08-24 Siemens Ag Switching resistor for an electrical switching device
US20060273876A1 (en) * 2005-06-02 2006-12-07 Pachla Timothy E Over-temperature protection devices, applications and circuits
US20100255353A1 (en) * 2008-12-15 2010-10-07 Mcdonald Robert C Thermal switch material suitable for use in controlling short circuits in lithium-ion batteries and method of making the thermal switch material
US8529729B2 (en) 2010-06-07 2013-09-10 Lam Research Corporation Plasma processing chamber component having adaptive thermal conductor
DE102011053415A1 (en) * 2011-09-08 2013-03-14 Phoenix Contact Gmbh & Co. Kg Surge protection device
EP2933577B1 (en) 2014-04-14 2017-12-06 Mahle Behr France Rouffach S.A.S Electric heating device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2331708A1 (en) * 1973-06-22 1975-01-16 Gerd Rudi Willi Ebinger Overload protection circuit with PTC resistor in series with load - uses sharp step in resistor temperature resistance characteristics
US4329726A (en) * 1978-12-01 1982-05-11 Raychem Corporation Circuit protection devices comprising PTC elements
FR2506067A1 (en) * 1981-05-15 1982-11-19 Alsthom Atlantique High voltage circuit breaker - where main switch has by=pass circuit contg. rows of resistors employed to quench arc when switch is opened

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4017715A (en) * 1975-08-04 1977-04-12 Raychem Corporation Temperature overshoot heater
US4177376A (en) * 1974-09-27 1979-12-04 Raychem Corporation Layered self-regulating heating article
US4421582A (en) * 1975-08-04 1983-12-20 Raychem Corporation Self-heating article with deformable electrodes
US4246468A (en) * 1978-01-30 1981-01-20 Raychem Corporation Electrical devices containing PTC elements
US4346424A (en) * 1980-02-22 1982-08-24 Eaton Corporation Electronic remote control D.C. power controller and circuit breaker
US4574188A (en) * 1982-04-16 1986-03-04 Raychem Corporation Elongate electrical assemblies
GB8602507D0 (en) * 1986-02-01 1986-03-05 Micropore International Ltd Electric radiation heater

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2331708A1 (en) * 1973-06-22 1975-01-16 Gerd Rudi Willi Ebinger Overload protection circuit with PTC resistor in series with load - uses sharp step in resistor temperature resistance characteristics
US4329726A (en) * 1978-12-01 1982-05-11 Raychem Corporation Circuit protection devices comprising PTC elements
FR2506067A1 (en) * 1981-05-15 1982-11-19 Alsthom Atlantique High voltage circuit breaker - where main switch has by=pass circuit contg. rows of resistors employed to quench arc when switch is opened

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5644283A (en) * 1992-08-26 1997-07-01 Siemens Aktiengesellschaft Variable high-current resistor, especially for use as protective element in power switching applications & circuit making use of high-current resistor
DE4340632A1 (en) * 1993-11-30 1995-06-01 Abb Patent Gmbh Electrical switching device
FR2716754A1 (en) * 1994-01-31 1995-09-01 Gen Electric Current limiter with calibration module.
EP0749140A1 (en) * 1995-06-13 1996-12-18 Gec Alsthom T Et D Sa Interruption device for high-tension DC
FR2735611A1 (en) * 1995-06-13 1996-12-20 Gec Alsthom T & D Sa DEVICE FOR CUTTING A HIGH VOLTAGE DIRECT CURRENT
EP0780849A2 (en) 1995-12-23 1997-06-25 Abb Research Ltd. Process of manufacturing a PTC resistor material
DE19548741A1 (en) * 1995-12-23 1997-06-26 Abb Research Ltd Process for the production of a material for PTC resistors
DE19702094A1 (en) * 1997-01-22 1998-07-23 Abb Research Ltd Circuit breaker
US6038117A (en) * 1997-01-22 2000-03-14 Abb Research Ltd. Power switching apparatus
DE19702094B4 (en) * 1997-01-22 2008-01-24 Abb Research Ltd. Power switching device

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CA1331399C (en) 1994-08-09
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ATE122827T1 (en) 1995-06-15
US4967176A (en) 1990-10-30
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KR900702614A (en) 1990-12-07
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EP0429489B1 (en) 1995-05-17

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