EP0335617A2 - Limitateur de courant pour éléments chauffants à couche épaisse - Google Patents

Limitateur de courant pour éléments chauffants à couche épaisse Download PDF

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Publication number
EP0335617A2
EP0335617A2 EP89302961A EP89302961A EP0335617A2 EP 0335617 A2 EP0335617 A2 EP 0335617A2 EP 89302961 A EP89302961 A EP 89302961A EP 89302961 A EP89302961 A EP 89302961A EP 0335617 A2 EP0335617 A2 EP 0335617A2
Authority
EP
European Patent Office
Prior art keywords
track
tracks
temperature
heating element
thick film
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.)
Granted
Application number
EP89302961A
Other languages
German (de)
English (en)
Other versions
EP0335617B1 (fr
EP0335617A3 (fr
Inventor
Simon Neville Balderson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thorn EMI PLC
Original Assignee
Thorn EMI PLC
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 Thorn EMI PLC filed Critical Thorn EMI PLC
Priority to AT89302961T priority Critical patent/ATE98082T1/de
Publication of EP0335617A2 publication Critical patent/EP0335617A2/fr
Publication of EP0335617A3 publication Critical patent/EP0335617A3/fr
Application granted granted Critical
Publication of EP0335617B1 publication Critical patent/EP0335617B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
    • H05B3/74—Non-metallic plates, e.g. vitroceramic, ceramic or glassceramic hobs, also including power or control circuits
    • H05B3/748—Resistive heating elements, i.e. heating elements exposed to the air, e.g. coil wire heater
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/26—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/002—Heaters using a particular layout for the resistive material or resistive elements
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/002—Heaters using a particular layout for the resistive material or resistive elements
    • H05B2203/005—Heaters using a particular layout for the resistive material or resistive elements using multiple resistive elements or resistive zones isolated from each other
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/013—Heaters using resistive films or coatings
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/017—Manufacturing methods or apparatus for heaters
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/019—Heaters using heating elements having a negative temperature coefficient

Definitions

  • This invention relates to a heating element comprising a thick film electrically resistive track, the thick film being formed of a base metal and a glass.
  • such a heating element be formed by depositing one or more thick film tracks on a glass ceramic surface of a composite support member, the track or tracks then being overglazed with a glass ceramic material for protection and to allow high temperature stable operation.
  • One or a number of such heating elements may provide one or a number of hot-plate elements in a hob-top or alternatively a heating element may be mounted closely adjacent the underside of a glass ceramic cooktop to provide a heated area on the cooktop. More than one such heating element or a unitary support member bearing more than one heating element can be used to provide more than one heated area on the glass ceramic cooktop.
  • a particularly suitable thick film for such applications includes nickel as base metal and will operate at the necessary power densities.
  • An advantage of a heating element made of such a thick film, as disclosed in our copending EP 0286215A, is its high temperature coefficient of resistance (TCR), i.e. in excess of 0.006 per degree C in the temperature range of from 0°C to 550°C, which provides for rapid heat-up and effective self-regulation.
  • TCR temperature coefficient of resistance
  • the associated problem of the high TCR is that when the heating element is activated, there is a high current surge which may be up to five times the operating current of the heating element and may be sufficient to blow the fuse in many high power appliances.
  • a cooker hob consisting of e.g. four such heating elements would have to be designed so that the elements could not be switched on within a few seconds of each other. Such control is expensive and could offset the low cost advantages of the heating element itself.
  • a range of thick films have been developed which utilise a base metal and have a low TCR. Such low TCR thick films may be used for heating elements and will meet the requirements for most applications. However their power handling characteristics are significantly worse than those for a thick film heating element in which the base metal is nickel.
  • a heating element comprising a plurality of thick film electrically resistive tracks, the plurality of tracks including a first track for electrical connection to a power supply and a second track, at least one of said first and said second tracks being made of a thick film having in the temperature range of from 0°C to 550°C a temperature coefficient of resistance in excess of 0.006 per degree C, wherein a means for electrically connecting said first and said second tracks in parallel comprises a component which depends on temperature such that, in use, the current flowing in said second track increases with the temperature of said first track.
  • the first and second tracks become electrically connected in parallel, allowing current to flow in the second track.
  • the first track has a resistance which is higher than that of the first and second tracks electrically connected in parallel. Accordingly, the current initially drawn, and any current surge, which is characteristic of the resistance of the first track because of the temperature dependence of the means for electrically connecting, is less than would be the case if the first and second tracks were electrically connected in parallel when the heating element was initially connected to the power supply.
  • the first track which is electrically connected to the power supply when the heating element is activated may have a high TCR. In this case, the heat up of the heating element would be more rapid when first activated.
  • the temperature-dependent component is provided by a material having a negative temperature coefficient of resistance (NTC) and so is self-regulating with temperature.
  • NTC negative temperature coefficient of resistance
  • a heating element 1 comprises a plurality of thick film tracks 2, 4, 6 applied to a substrate 7.
  • the tracks 2, 4, 6 are made of a nickel thick film having a high TCR as described in our copending EP 0286215. Thick films including cobalt or iron as base metal have similarly high TCRs and may also be used to produce tracks for heating elements.
  • the track 2 has terminals 8, 10 for connection to an external power supply via electrical connectors (not shown).
  • the track 2 is connected to the other tracks 4, 6 and they to each other at each end by components formed as bridges 12, 14 of a thick film material containing a composition which has an NTC of resistance.
  • Suitable compositions include the following:
  • the NTC bridges 12, 14 have a high resistance compared to the tracks 2, 4, 6 and thus the tracks 2, 4, 6 are effectively insulated from each other.
  • the heating element When power is applied to the heating element there is a small current surge characteristic of the track 2 connected to the power supply. As the temperature increases, the current in this track 2 decreases (due to its increasing resistance) but at the same time the resistance of the NTC bridges 12, l4 decreases, thereby allowing increased current flow in the other tracks 4, 6.
  • the net result is an overall current flow to the heating element 1 which shows no large increase or decrease with change in time or temperature.
  • the principle of this is illustrated schematically in Figure 2 which shows variation of current with temperature for the following heating elements:
  • control of the NTC material characteristics and the track geometry would allow design of a heating element with a virtually flat current response with temperature whatever the TCR value of the track material.
  • FIG. 3 a suitable configuration for connection of tracks 16, 18 and an NTC bridge 20 is shown in which the NTC bridge 20 is sandwiched between the tracks 16, 18 on a substrate 22.
  • the tracks and NTC bridges are protected from oxidation by an overglaze layer (not shown), allowing high temperature stable operation.
  • NTC bridges need only be provided at one end of the thick film tracks, at the other end the tracks being electrically connected by conventional means.
  • An NTC bridge could be provided only between the track 2 and its adjacent track 4 to limit current surge.
  • a plurality of tracks could be provided between the connections to the external power supply and the first NTC bridge to determine the extent of current surge.
  • each NTC bridge could form part of a track and be connectable in parallel which would allow the selective connection of the tracks to the power supply to vary the operating temperature of the heating element.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Resistance Heating (AREA)
  • Surface Heating Bodies (AREA)
  • Control Of Resistance Heating (AREA)
EP89302961A 1988-03-25 1989-03-23 Limitateur de courant pour éléments chauffants à couche épaisse Expired - Lifetime EP0335617B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT89302961T ATE98082T1 (de) 1988-03-25 1989-03-23 Strombegrenzung bei dickschichtfilmheizelementen.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB888807139A GB8807139D0 (en) 1988-03-25 1988-03-25 Current source limitation for thick film heating elements
GB8807139 1988-03-25

Publications (3)

Publication Number Publication Date
EP0335617A2 true EP0335617A2 (fr) 1989-10-04
EP0335617A3 EP0335617A3 (fr) 1991-03-20
EP0335617B1 EP0335617B1 (fr) 1993-12-01

Family

ID=10634106

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89302961A Expired - Lifetime EP0335617B1 (fr) 1988-03-25 1989-03-23 Limitateur de courant pour éléments chauffants à couche épaisse

Country Status (4)

Country Link
EP (1) EP0335617B1 (fr)
AT (1) ATE98082T1 (fr)
DE (1) DE68911008T2 (fr)
GB (1) GB8807139D0 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2049180A2 (es) * 1992-09-17 1994-04-01 Eika S Coop Ltda Mejoras en calefactores radiantes.
WO1996017496A1 (fr) * 1994-11-26 1996-06-06 Pifco Limited Perfectionnements apportes a des elements a couche epaisse
GB2307384A (en) * 1995-11-17 1997-05-21 Ceramaspeed Ltd Damping initial currents using NTC ballast resistance
GB2307385A (en) * 1995-11-17 1997-05-21 Ceramaspeed Ltd Radiant heater having resistance heating element with dynamic TCR
WO2001093638A1 (fr) * 2000-05-30 2001-12-06 Otter Controls Limited Ameliorations apportees a des elements de chauffage electrique

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2777930A (en) * 1954-04-28 1957-01-15 Nathanson Max Heating unit
US3396055A (en) * 1965-04-16 1968-08-06 Vitreous Steel Products Compan Radiant heating panels and resistive compositions for the same
EP0208823A1 (fr) * 1985-07-15 1987-01-21 Kanthal AB Résistance de chauffage électrique
EP0227405A2 (fr) * 1985-12-16 1987-07-01 RAYCHEM CORPORATION (a Delaware corporation) Résistance chauffante à autorégulation utilisant des composants réactifs

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2777930A (en) * 1954-04-28 1957-01-15 Nathanson Max Heating unit
US3396055A (en) * 1965-04-16 1968-08-06 Vitreous Steel Products Compan Radiant heating panels and resistive compositions for the same
EP0208823A1 (fr) * 1985-07-15 1987-01-21 Kanthal AB Résistance de chauffage électrique
EP0227405A2 (fr) * 1985-12-16 1987-07-01 RAYCHEM CORPORATION (a Delaware corporation) Résistance chauffante à autorégulation utilisant des composants réactifs

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2049180A2 (es) * 1992-09-17 1994-04-01 Eika S Coop Ltda Mejoras en calefactores radiantes.
WO1996017496A1 (fr) * 1994-11-26 1996-06-06 Pifco Limited Perfectionnements apportes a des elements a couche epaisse
GB2307384A (en) * 1995-11-17 1997-05-21 Ceramaspeed Ltd Damping initial currents using NTC ballast resistance
GB2307385A (en) * 1995-11-17 1997-05-21 Ceramaspeed Ltd Radiant heater having resistance heating element with dynamic TCR
GB2307384B (en) * 1995-11-17 2000-05-24 Ceramaspeed Ltd Infra-red heater
GB2307385B (en) * 1995-11-17 2000-05-24 Ceramaspeed Ltd Radiant electric heater
WO2001093638A1 (fr) * 2000-05-30 2001-12-06 Otter Controls Limited Ameliorations apportees a des elements de chauffage electrique

Also Published As

Publication number Publication date
EP0335617B1 (fr) 1993-12-01
GB8807139D0 (en) 1988-04-27
DE68911008T2 (de) 1994-06-16
DE68911008D1 (de) 1994-01-13
ATE98082T1 (de) 1993-12-15
EP0335617A3 (fr) 1991-03-20

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