EP0105770A1 - Industrielle elektrische Heizumrahmung - Google Patents

Industrielle elektrische Heizumrahmung Download PDF

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Publication number
EP0105770A1
EP0105770A1 EP83401728A EP83401728A EP0105770A1 EP 0105770 A1 EP0105770 A1 EP 0105770A1 EP 83401728 A EP83401728 A EP 83401728A EP 83401728 A EP83401728 A EP 83401728A EP 0105770 A1 EP0105770 A1 EP 0105770A1
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EP
European Patent Office
Prior art keywords
heating
unit
resistor
value
enclosure
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
EP83401728A
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English (en)
French (fr)
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EP0105770B1 (de
Inventor
Jean-Louis Morice
Robert Pernelle
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.)
Selas SA
Original Assignee
Selas SA
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Publication date
Application filed by Selas SA filed Critical Selas SA
Publication of EP0105770A1 publication Critical patent/EP0105770A1/de
Application granted granted Critical
Publication of EP0105770B1 publication Critical patent/EP0105770B1/de
Expired legal-status Critical Current

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    • 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
    • H05B1/00—Details of electric heating devices
    • H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
    • H05B1/0227—Applications
    • H05B1/023—Industrial applications
    • 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
    • H05B3/0014—Devices wherein the heating current flows through particular resistances

Definitions

  • the present invention relates to an industrial electric heating device, in particular for an oven and other heat treatment enclosure or drying installation, of the type comprising radiant panels, themselves heated by electrical resistors, the latter being supplied by means of semiconductor elements, such as thyristors.
  • the invention also relates to a method for implementing the above-mentioned device.
  • the installation has n areas of. heating, n being at most equal to the number of radiant panels.
  • These installations may include, for controlling the current in the heating resistors of each radiant panel, a power semiconductor unit generally constituted by power thyristors controlled by a regulation chain depending for example on the temperature difference. between a setpoint and the value actually measured in the heating chamber by temperature sensors.
  • thyristors and their electronic control device are generally placed in specific boxes, most often assembled in distribution boards in a specialized room and connected to the corresponding resistors by means of electric power cables. Given the often difficult environment of this type of installation in which heavy objects or numerous parts are handled, these cables are often buried in distribution channels specially made for this purpose. It follows from these provisions that the lengths of power cables used are generally large and that the cost of such installations is high.
  • the regulation chain of the central control device comprises a certain number of circuits: cold junction correction, analog-digital converters (A / D) intended to convert the analog signals received from the sensors into digital signals which can then be processed by a computer or microprocessor.
  • the computer acquires these measurements as well as those of the set-point temperatures then, using the calculation algorithm, calculates a regulation value R specific to each heating zone.
  • these regulation values R are reconverted into analog signals by a D / A converter, then these signals are applied to interface circuits before controlling the switching on or off of the thyristors.
  • the object of the present invention is to remedy. to the aforementioned drawbacks by presenting an electric heating device by radiant panels and an implementation method which make these installations more economical, more reliable and more flexible in their implementation by the user.
  • the industrial electric heating device comprising at least one radiant panel which carries at least one heating resistor, this panel being connected to a power semiconductor unit controlling the supply of the resistor, this unit being controlled by electronic temperature regulation means is characterized in that each power semiconductor unit is directly placed on the radiant panel and in that it is connected to the same central electronic device for remote control of the radiant panels.
  • the heating resistor is connected directly to the terminals of the semiconductor control unit but placed on the opposite side thereof relative to the radiant panel.
  • the semiconductor control unit is advantageously constituted by thyristors mounted head to tail with which are associated on the radiant panel their static control relays.
  • the power control part is fully integrated into the panel which constitutes a modular, complete and separate element from the central electronic control device.
  • the central electronic device for controlling the semiconductor units comprises a computing unit such as a microprocessor or a computer, the input of which is connected to means supplying signals indicative of the temperature.
  • a computing unit such as a microprocessor or a computer, the input of which is connected to means supplying signals indicative of the temperature.
  • various heating resistors or an arbitrarily chosen signal whose output delivering the control signals is directly connected to the power semiconductor control means of the corresponding panels.
  • a permanent control value R attached to each panel is continuously compared in the computer - or the microprocessor - to a value C which is cyclically variable from zero to a maximum value N , incremented at a frequency F, the range of evolution of R being in all cases between O and N, a binary signal O being delivered when R is less than C and a binary signal 1 when R is greater than C, said binary signals then generating a zero voltage for the binary signal O and a positive voltage - for example 15 volts - for the binary signal 1, these voltages being then applied directly to the static thyristor control relays for the delivery of current wave trains to the heating resistance.
  • This R value can be either calculated by the calculation unit from the signals indicative of the temperature of the heating resistors, or chosen arbitrarily.
  • the radiant panel 1 constitutes the basic modular element for the production of the wall A of the enclosure of a heat treatment oven or of a drying installation, for example of paint materialized by the dotted lines 2a and 2b.
  • the radiant panel 1 has the general shape of a parallelepipedal block 3 made of refractory material, preferably fibrous material which constitutes the thermal insulation of the installation.
  • a resistor 4 cut into zig-zag strips is applied by its widest face to the face of the block 3 forming the wall 2a situated towards the heating enclosure A and at its ends 5 folded over the lateral faces of the block 3.
  • This resistance has two tabs 6a, 6b, having holes 7a, 7b for its connection to supply conductors 23.
  • the outer face of the panel 1 carries a metal carcass 15, constituted by two plates 15a, 15b separated by spacers 18 and which supports the power semiconductor unit 39 and its annexes, fixed on the plate 15b.
  • This unit essentially comprises two thyristors 8, mounted head to tail and compressed strongly, in known manner, between two elements of finned radiator 9 which ensure their cooling.
  • the two thyristors are oversized.
  • thyristors of nominal size 500 A are used for normal operation at 130 A.
  • the radiators 9 must likewise have a sufficient cooling surface so that the temperature of the thyristors 8 does not exceed 110 ° C.
  • the support force of the radiators 9 is for example of the order of 1 ton. Mechanical mounting with Belleville washers, not shown, keeps the contact force constant, even if the temperature of the assembly changes.
  • the electrical part of the panels 1 also includes a surge limiter circuit 10 and a power fuse 11.
  • the control circuit 12 of the thyristors receive the temperature regulation signals from a central electronic control device 31 (FIG. 3 ) which will be described later.
  • a temperature sensor 13 such as a thermocouple which is connected by a line 14 to the central device 31.
  • the flanges 19 have holes 21 allowing their connection with the harologous flanges for supporting the adjacent radiant panels 1. It is thus possible to produce, with an external metal frame, not shown, a heating modular wall, each panel 1 of which is removable and whose external wall 2b, opposite the heating wall 2a, is accessible for the wiring of the radiant panels.
  • the thermal insulation between the adjacent panels is completed by simply sliding between them sheets of fibrous insulation, of adequate thickness, folded and forming a joint.
  • the power supply of the radiant panel 1 is provided by a single power cable 30 ( Figure 3) which runs along the wall 2b of the heating enclosure and on which are connected for each radiant panel 1 the conductor 23a d power supply of the resistor 4, and the power supply conductor 22 of the semiconductor unit formed by the thyristors 8, the conductor 23b being connected between the protective fuse 11 of the latter and the other terminal of the resistor 4.
  • the single cable 30 which provides the power supply is advantageously of the three-phase type and it serves all of the radiant panels 1, constituting separate heating zones Zl ... Zn distributed along the enclosure A.
  • the radiant panels 1 are alternately connected with a phase rotation (see FIG. 3) on the cable 30 for well-known load balancing reasons.
  • FIG 3 there is shown the general diagram of an installation according to the present invention thus comprising n heating zones corresponding to the n radiant panels 1 used, of which only the extreme panels l 1 and l n have been shown with their thyristor control units 39, their heating resistors 4 and their thermocouples 13 connected to cables 14.
  • the installation comprises a central electronic control device, common to all the radiant panels 1, at l n and which essentially comprises a calculation unit, such as a computer or a microprocessor 31, shown diagrammatically with its processor and its peripherals 32, the data bus 33, the address bus 34, the measurement acquisition circuits 35 and the address validation circuit 36 for the n heating zones.
  • the connection between the radiant panels 1 of the n zones Z 1 to Z and the calculation unit 31 is provided at the input by the conductors 14 connected between the temperature sensors 13 and the data acquisition circuit 35 and on the other hand, at the output by the control links 38 transmitting the output signals from the calculation unit 31 of the address validation circuit 36 to the thyristor control units 39.
  • Each thyristor control unit 39 as shown in FIG. 4 comprises a power stage and a control stage mounted on a printed circuit.
  • the power stage essentially comprises the two thyristors 8 mounted head to tail protected by the common fuse 11 placed in the supply circuit 22.
  • the thyristors 8 comprise a trigger 44 connected by each of them to a static relay 45 by l 'through a current limiting resistor 46.
  • These solid state relays 45 are such that they can be controlled by a low level signal, such as that delivered by a computer and they include an electro-diode luminescent 47 which controls a photo-transistor 48 by an opto-electronic coupling thus achieving a total galvanic break between the circuits of the computing unit 31 and the power circuits.
  • the power supply circuit for light-emitting diodes 47 comprises a ground 49 which is connected to the ground of the computing unit 31, the connection with the central control stage being thus effected by a single conductor 38.
  • FIG. 5 schematically represents the operating sequences for the purpose of explaining the process.
  • the analog signals representing the temperatures of the n heating zones Z 1 ... Z n emitted by the sensors 51 (51a, 51b, ... 51n) - are transmitted to isolation circuits , linearization and cold junction compensation 52 before being transformed into digital signals by the analog / digital converters 53.
  • All of these circuits mainly form the data acquisition circuits 35 (see FIG. 3).
  • the values thus established are entered and stored in registers 54 and are refreshed each time the measurement sensors are scanned.
  • Values corresponding to the set temperatures that is to say the temperatures which it is desired to obtain on the resistances of each of the zones are entered using the keyboard of the calculation unit 31 in the register 55. These temperatures can be different or identical for all or part of the n zones of the oven or of the drying tunnel.
  • the scanning times are defined by a clock internal to the device 62, of adjustable frequency which controls all of the operations over time.
  • the signals of the registers 54, 55, 56 are then transmitted on each scan to the processing unit 57 which delivers the regulation value R. This value is entered and stored in a register 59.
  • a register 58 makes it possible to enter arbitrarily chosen values of R, that is to say without reference to the temperature of the heating resistors 4. These values are directly entered in register 58 using the computer keyboard.
  • the heating device delivers a fixed power, fraction or all of its maximum power, solely as a function of the value R applied. Whatever the mode of establishment of R, calculated or chosen, the subsequent steps of the method are then identical.
  • the method then implements a set of zone counters 60 controlled by the internal clock 62 of adjustable frequency F, whose range of evolution from 0 to a value N is adjustable. (When the counter reaches the prefixed value N, it is reset to 0, then starts its cycle again).
  • N chosen are entered using the computer keyboard and stored in a register 61 to be transmitted to the counter 60.
  • a comparator 59 will then carry out at each incrementation step of the counter 60 which corresponds to a scan of the temperatures of the heating resistances of the device, a comparison between the value of R calculated or chosen for each zone and the value C of the zone counter (variable between O and N) to deliver a binary signal S.
  • the aim of the previously mentioned scale coefficient KE is, in the context of a given temperature regulation, to bring the calculated value of R into the range 0, N of evolution of the counter 60 corresponding thereto.
  • a binary signal O is delivered when R is less than C and a signal 1 when R is greater than C.
  • This signal 1 or 0 is then applied to a set of voltage generator memory flip-flop circuits 63, also comprising one circuit per zone. These circuits deliver an adjustable voltage T, for example 15 volts.
  • This voltage T delivered on the outputs of the computer or of the microprocessor is then transmitted by the shielded cable 38 to be applied to the light-emitting diodes 47 of the static relays 45 for controlling the triggers of the power thyristors 8.
  • the calculation unit 31 has a mass connected to the ground 49 of the solid state relays 45.
  • the regulation value R of a zone varies over time depending on various parameters such as size and shape of the parts to be heated, losses from the oven, date of introduction of the part or parts, introduction of new parts, possibly speed of scroll parts, positions within the heating cycle ...
  • FIG. 7 illustrates the operation of the thyristors 8 under the influence of the voltage signals T delivered by the computer 31.
  • a voltage signal T - for example 15 volts - is delivered by the flip-flop memory generator circuits 63 to the solid state relays 45, these apply the starting voltage to the thyristors 8.
  • these will only start when the voltage which is applied to authors terminals 22 goes to 0.
  • each of the thyristors 8 thus contributes to the passage of consecutive half-wave alternations which form the wave trains 70 of current applied to the resistor 4.
  • the known embodiments comprise at the output of the computer interface circuits including digital / analog converters, the multiplicity of which significantly reduces the reliability of the installation.
  • the connection between the computer and the semiconductor units is carried out without any intermediate circuit significantly reducing these risks of breakdowns.
  • the device of the invention makes it possible to obtain this result simply by choosing a value of N much greater than the regulation value R.
  • N a short current flow time t followed by a cut-off time t 0 long (see Figure 6) which will correspond well to the application of a small percentage of the maximum power of the installation.
  • t a cut-off time t 0 long
  • the fine regulation will then intervene with the variation of the regulation value R.
  • the device operates as a power limiter which can only be obtained with the known devices by acting in a much more complex and costly manner on the parameters of the regulation algorithm.
  • the means provided by the invention make it possible to control the resistors 4 as well with a high-performance computer as with an 8-bit mini-computer. Only the execution speed will be changed. For example, the time taken to regulate the temperature of an area with a 16-bit minicomputer is 1 millisecond.
  • the invention is not limited to the embodiments described above and it is possible to make variant embodiments.
  • the heating resistors in strips 4 could be replaced by helical or wave resistors.
  • static relays with light-emitting diodes and phototransistors could be replaced by conventional miniature relays with very low current consumption.

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  • Control Of Resistance Heating (AREA)
EP83401728A 1982-09-24 1983-08-31 Industrielle elektrische Heizumrahmung Expired EP0105770B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8216108 1982-09-24
FR8216108A FR2533791A1 (fr) 1982-09-24 1982-09-24 Dispositif de chauffage electrique industriel a commande electronique et procede s'y rapportant

Publications (2)

Publication Number Publication Date
EP0105770A1 true EP0105770A1 (de) 1984-04-18
EP0105770B1 EP0105770B1 (de) 1988-06-01

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ID=9277709

Family Applications (1)

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EP83401728A Expired EP0105770B1 (de) 1982-09-24 1983-08-31 Industrielle elektrische Heizumrahmung

Country Status (3)

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EP (1) EP0105770B1 (de)
DE (2) DE105770T1 (de)
FR (1) FR2533791A1 (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0304333A1 (de) * 1987-08-21 1989-02-22 BRITISH TELECOMMUNICATIONS public limited company Heizvorrichtung
WO1997017583A1 (en) * 1995-11-07 1997-05-15 Sandvik Aktiebolag (Publ) Power control for furnace
EP1335631A1 (de) * 2002-01-31 2003-08-13 Gefran S.p.A. Vorrichtung für die Stromversorgung und die Steuerung von elektrischen Heizwiderstände in Arbeitsmaschinen
US8544923B2 (en) 2008-09-29 2013-10-01 Engineered Lifting Technologies, Inc. Lifting assembly

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2067342A1 (de) * 1969-11-17 1971-08-20 Borg Warner
FR2258758A1 (en) * 1974-01-17 1975-08-18 Gachot Sa Centralised control for central heating radiators - has ambient temp. controlled delayed switching units
FR2298248A1 (fr) * 1975-01-17 1976-08-13 Carrier Corp Circuit de commande d'appareil generateur de chaleur fonctionnant a l'electricite
US4090062A (en) * 1976-07-12 1978-05-16 Phillips Control Corp. Energy demand controller and method therefor
FR2393357A1 (fr) * 1977-06-02 1978-12-29 Lockheed Electronics Co Regulateur de puissance delivree a des charges multiples, equipe d'un calculateur en temps partage

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2067342A1 (de) * 1969-11-17 1971-08-20 Borg Warner
FR2258758A1 (en) * 1974-01-17 1975-08-18 Gachot Sa Centralised control for central heating radiators - has ambient temp. controlled delayed switching units
FR2298248A1 (fr) * 1975-01-17 1976-08-13 Carrier Corp Circuit de commande d'appareil generateur de chaleur fonctionnant a l'electricite
US4090062A (en) * 1976-07-12 1978-05-16 Phillips Control Corp. Energy demand controller and method therefor
FR2393357A1 (fr) * 1977-06-02 1978-12-29 Lockheed Electronics Co Regulateur de puissance delivree a des charges multiples, equipe d'un calculateur en temps partage

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0304333A1 (de) * 1987-08-21 1989-02-22 BRITISH TELECOMMUNICATIONS public limited company Heizvorrichtung
WO1989001401A1 (en) * 1987-08-21 1989-02-23 British Telecommunications Public Limited Company Heating device
US5870423A (en) * 1995-11-06 1999-02-09 Sandvik Ab Individual heating element power control for a furnace
WO1997017583A1 (en) * 1995-11-07 1997-05-15 Sandvik Aktiebolag (Publ) Power control for furnace
EP1335631A1 (de) * 2002-01-31 2003-08-13 Gefran S.p.A. Vorrichtung für die Stromversorgung und die Steuerung von elektrischen Heizwiderstände in Arbeitsmaschinen
US8544923B2 (en) 2008-09-29 2013-10-01 Engineered Lifting Technologies, Inc. Lifting assembly

Also Published As

Publication number Publication date
EP0105770B1 (de) 1988-06-01
FR2533791A1 (fr) 1984-03-30
FR2533791B1 (de) 1985-01-18
DE105770T1 (de) 1984-08-16
DE3376951D1 (en) 1988-07-07

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