EP1665891A1

EP1665891A1 - Induction heater

Info

Publication number: EP1665891A1
Application number: EP04785416A
Authority: EP
Inventors: Jovan Adnadj
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-08-29
Filing date: 2004-08-27
Publication date: 2006-06-07
Also published as: WO2005022955A1

Abstract

The subject invention relates to the field of electrothermics and it solves a technical problem of construction of an electrical induction heater which has a high efficiency and is simple for manufacture and use, and which during work use a clean filtered air and is heating the surrounding area without higher themperature oscilations during its work. This has been achived with induction heater made so that the heating body (3) is realized as a modified three-phase transformer, to which yoke (13) are connected cyllindrical steel cores (33) in which is after current flow through windings (32) wind up on the thermoinsulated chamotte coils (17), (18) i (19), under effect of alternating electromagnetic field form eddy currents, warm it up to themperature ≈ 350 °C. Whichafter warmed air around the core (33) forced by fan (4) flow through three way ventilation passage (5) from the first coil (17) till the last coil (19) on which is placed an exhaust tube (34) with opening (25), through which is further going into surrounding space heating it.

Description

IND UCTION HE A TER

TECHNICAL FIELD

The subject of the invention, in general, belongs to the field of heating by electrical energy, i.e to electrothermics, and particularly relates to the induction heaters. According to the International Patent Classification (LPC), seventh edition Int.Cl.⁷, the subject of the invention is classified into H 05B 6/02, which symbol relates to heating by electrical, magnetic or electromagnetical field - induction heating, as well into H 05B 6/10 which relates to devices for indiction heating i.e. into H 05B 6/36 which relates to coil arrangements. Because of reason that heat in the heater, according to the invention, is made by use of an iron core through which are flowing Foucault currents and is functioning on the principle of circuits with coils and closed ferromagnetic core, the subject invention may be classified by additional secondary classification symbol F 27D 11/06, which relates to induction heating, in which the material being heated or its container or the elements embodied therein, form the secondary of a transformer.

TECHNICAL PROBLEM

Technical problem to be solved by the present invention consists in: how to built an electrical induction heater which enable economical use of electric power for heating of home and business premises, where besides, such heater is working continually without noticeable decrease of the temperature, enable rapid air heating in the heated area, is . simultaneously simple for manufacture and maintenance^' and in exploitation enable, as from heating aspect, by passing through a clean filtered air, a full comfort for work and stay within area heated with it. STATE OF THE ART

Nowadays are known different structures of heating devices made as electric heating apparatus used for heating the working or living areas. On some of these heaters, heating element is mounted on insulators fixed on the metal frame or the heating element is built from conductors settled within interiors of rods or tubes made of insulating materials. Number of heating elements in the heating apparatus which are in the common use is about two to three, where these are arranged parallely one over another within height of the heater. There exist the heating apparatus with electrical wire conductors arranged in one or more circles, like in one or in more planes, for example, winded spirally on the cone insulator. Nowadays in the massive use are heating apparatus known as thermal storage room heaters, which thermical effect relates to transformation of electrical into thermal energy (under Joule Law). Produced heat quantity depends of current intensity, of voltage and of conductor's resistance, and thanks to ability of furnace refractory panelling (made of chamotte or of special magnesite materials) accumulate most frequently at the time when it is most economical usually over-night using 'of-pea ' electricity. Thanking to the furnace refractory panelling a part of so accumulated heat may later be delivered in defined time period, mostly in the day time when the users reside in the areas heated themwith. All above mentioned heater apparatus and thermal storage room heaters have some disadvantages which are mostly reflected in the following: their thermical effect is insufficient; heaters often burn out; relating to the investments the life time of the use period is very short; the lasting efficiency is low; unpleasant smell may occure because of dust burning and from eventualy burned insects etc. Just above enumerated disadvantages have induced authors to construct new heating device which would be light, would produce heat rapidly and without great temperature oscillations, and which besides for the transformation and transfer of electrical into thermal energy use contactless mode of functioning. This is by the opinion of authors achievable only by induction heating. Such mode of heating, by authors knowledge is in use only in industry for ore melting, in manufacture of plastics likewise in different welding proceedings. In spite of a very careful search within home and international patent documentation and proffesional literature in the field of electrothermics, i.e. in the field of producing the heat by electromagnetic induction, it was not found not any similar technical solution comparative with induction heater of the present invention. DISCLOSING THE ESSENCE OF THE INVENTION Above defined technical problem is solved by new constructed induction heater. The essence of the invention reflects in that the electric induction heater, according to author's idea, is accomplished so that by its use may be achieved a high degree of electric efficiency (μc), it is realized as three-phase transformer with three reciprocaly inteconnected cylindrical steel cores placed in thermoinsulated chamotte coils. These coils beside their thermoinsulating function, use as parts of ventilation block of the device and are accomlished as threelayered coaxial mutualy spaced chamotte tubes, where the most wide one is wraped arround with copper spiral (inductor). The coils are connected in star- ■ connection and power suply is three-phase voltage (3 x 380V 50 Hz). The most narrow chamotte tube, beside its use for placing arround it concentricaly fixed steel core, is through hose coupling connected to three-way ventilation block and enable that heated air arround the core under action of electric fan flow from space arround the first heating body over the middle heating body till the last heating body on which is placed an exhaust opening through which is blown out into surrounding space. The essence of the invention is represented in fact, that is for the heating of home or working areas or for the obtaining of a hot air which may be used for the different purposes utilized the principle of induction heating so that the heating body has been realized in form of a cylindrical steel core inserted into inductor. Exactly such core design has achieved a very high values of induction heating. Talcing into consideration that for such a case of induction heating may be applied the relations: where:

D - - diameter of inductor coil H - - height of inductor coil d - ■ diameter of core h - • height of core pl - specific resistivity of inductor p2 - specific resistivity of core. Since in the case which is given as the example of the carrying out of the invention, copper is used as inductor and a for the core is used steel with temperature over a Curie

^temperature, for which are applied relations D ~ d and H ~ h, supposing that relative magnetic permeabilities μl and μ2, of inductor and of core relates as μl ~ μ2, we shall have

Since in the given case is pl> p2, it is quite clear that the efficiency of such induction heating^" body is exceptionaly high i.e far over the values achieved by other methods of electrical heating The essence of the invention is also the fact that during working of the subject induction heater, we have practically three-purpose energy transformation (electric energy into electromagnetic field, than into eddy current and later into heat' energy) which only on the first sight seem as disadvantage. By measuring energy consumption used for working of induction heater and comparing these values with values received by measuring consumption of heaters which for heating use other ways of transformation electric into heat energy, easy may be established that elimination of energy losses, talcing rise from classic heat transfer in all broadly used heating bodies, has been achieved by contactless heating used in " subject invention. This represent a significant saving in behalf of advantageous heat gain. The essence of the invention is also the fact that device under author's idea is characterized by low thermical sluggishness and high velocity of heat spreading into surrounding space, by working without frequency coverter (on main frequency 50 Hz), which decrease production costs and electricity losses, as well on the possibility of working in inactive atmosphere even in vacuum. That what particularly, essentially difere device according to the invention from all known electric heaters is that the temperature on the devices cover during working mode when blows the heated air of ~ 90 °C, is only few degrees higher than the temperature of the air in room which is heated. This characteristic enable use of such materials for the production of covers like wood, plastics or similar, and in itself open wide possibilities for the designers work. The essence of the invention reflects also in that the thermoinsulation system of chamotte coils, on which are wound inductor windings, is realized with three mutually coaxially placed chamotte tubes, mutually spaced so that form air barriers which prevent coil overheating and its damage, wherewith is provided considerably longer life time. Relating to technical solutions known to author's by which is solved the problem of conversion of electrical into thermal energy, paiticularly in those working on convection principle, the subject invention has many advantages where as the most important are stated namely: - production of induction heater is simple and it is possible to be produced rapidly moreover it is not complex for handling and maintenance; - it is exceptionally reliable during work; - it has consumption four times lower than the consumption of thermal storage room heaters of the same installed power (without emitting heat by fan); - considering materials used for production of covers (wood, particle boards, plastics etc.) it is possible to insert it into each interior; - use of micro filters or application of of some other corresponding good filters on, inlet openings and a possibility of their simply replacement and periodical cleaning, has achived that exceptionally clean air is circulating during the process of room heating; - fans used for obtaining convection of hot air into surrounding space are so designed that the air flow through the heated space is almost laminar and without large turbulent air flow; - during work of so constructed heater there are no large temperature oscillations so that minimal and maximal temperatures moves within (+ -) few degrees; - device is completely noiseless; - for the invention according to the exemplary embodiment given in the present specification anticipated is use of main voltageof 3x380 V, frequency of 50 Hz, which means that the device is working without converter consequence of which is less total losses and lower productions price; - with minor changes (by bridging input feeding lines) the device may work using main voltage of 220 V, 50 Hz. BRIEF DESCRIPTION OF THE DRAWINGS

In order for the better understanding of the present invention, like in order of disclosing its embodiment in practice, author is exemplary reffering to the accompanying drawings relating to induction heater where: - Figure 1. is showing construction appearance of the subject induction heater in frontal view; - Figure 2. is presenting the electrical and functional diagram of the induction heater with^" designated flowing directions of warmed air; - Figure 3. is front view of induction heater; - Figure 4. show appearance of induction coil in horizontal cross-section V - V;

DETAILED DESCRIPTION OF THE INVENTION

Looking on the figures on the enclosed drawings it may be easy notified that the induction heater, according to the present invention, consists of metal housing 1, cover 2 of the heater, three heating bodies 3, fan 4, three-way ventilation passage 5, housing 6 of the control arrangement 7 and of a capacitive compensation arrangement 8. The housing 1 is made of sectional metal pipes, in form of quadrilateral frame which in its lower part has fixed, preferably by welding, a previously formed quadrilateral metal bottom 9 with wheels 12, on which are fixed by screws, transversaly positioned by ends of lateral sides, horizontal foots 10, in the middle of which, also preferably by welding, are fixed vertical supporting columns 11 of yoke 13. Heating body 3 is realized as modified three-phase transformer and is fixed to supporting columns 11 so that ends of the yoke 13 are inserted in the sectioned lateral holders 14 placed near bottom and near to upper ending of supporting columns 11, and later secured against displacement by tension screws 15. On the upper side of the yoke 13, in order of more easier handling during displacement (assembling and dismantling) of the heating body 3 are placed, near ends, a metal handles 16. The difference between a classic three-phase transformer and a heating body 3 reflects in, according to the author's idea, that instead of a classic yokes made of transformer plates for yoke 13 fixed a steel yokes 33 inserted into chamotte coils 17, 18 and 19. These coils are formed of three circular coaxially placed and mutually separated chamotte tubes 35, 36 i 37, which forms tubular passages 38, 39 and 40 fulfilled with air, where two outer tubular passages represent thermal insulators for copper windings 32 whilst through the tubular passage 38 between a steel yoke 33 and a chamotte tube 35, moved by fan 4, flows the air which than through ventilation passage first goes to the middle chamotte coil 18 and afterwards to the third chamotte coil 19, after which it goes , into surrounding space. Around widest outer tube 37 with flange strengthening 41 are coiled up a copper windings 32, mutually joined into star connection and linked to the main power supply. On the lower elongated end of the most narrow chamotte tube 35 is shipped a cylindrical connector 20, through which is placed yoke 13 where the, flange of this connector 20 is connected with flange of the output opening on housing of the fan 4, whilst on the upper end of this tube is settled upper cylindical connector 21 whos flange is realized so that is joimed with flange of the folded ventilation passage 22 which connect output ventilation opening of the first chamotte coil 17 with input opening of the second chamotte coil 18. ^'Middle derivative of heating body 3 by its construction is identical with its first derivative, so that is on the upper and its lower side limited by yoke 13, and the only difference is that on its lower end is placed a cylindrical connector 20 which flange is joined with flange of the lower folded ventilation passage 23 which connects it with lower input opening of the third chamotte coil 19. This coil is identical with previous two coils 17 i 18 except in its upper end where is placed upper cylindrical connector 24 which in prolongation pass into exhaust tube 34 with opening 25 on which is placed grate 39,. through which the hot air from heating body 3 of induction heater, powered by circulation forced by fan 4, goes into surrounding space heating it. Here should be mentioned that connections between coils 17, 18 and 19 and between corresponding cylindrical connectors on their upper and lower sides must be well tighted, where the packing in the exemplary embodiment is made with chamotte sand. Motor of the fan 4 and the sole housing of the fan are well known in the state of the art and therefore, like other standard parts of the device, would be shown within specification and accompanying drawings only in extent which is necessary for purpose in explanation of functioning of device and prove of the feasibility of invention, without particular explanation of its work. The power of fan 4 motor is designated in accordance with designed power of heating. Selection of motor's working mode for fan 4 may be done with switch 25 placed on the front side of the housing 6. Control arrangement 7, which is placed into smaller laterally positioned housing 6 preferably in form of an quadrilateral, includes the switch 26 also, which is used for turning-on of the contactors, selectable circuit breaker 27 with collars, through which is connected to the main supply 3 x 380 V, 50 Hz, and fan, switch 29 for turning on of fan, electric clock 28 and arrangement 8 of capacitive compensation made of capacitors CI, C2 and C3 connected into triangle. Rectangular plates which made cover 2 of the heater, are dismountable fixed by screws to housing 1 and may be made of materials inert to heat transfer (e.g. wood, particle plates, plastics and similar). On the lateral sides of the cover 2 are the handles 42 and 43 which enable easy manipulation with heater. By selection of materials, colors, patterns etc. for making the cover 2 is enabled to designers of the heater, creation of various models so that heaters could be as easy as possible inserted into different interiors. On the cover 2, which is during the work only slightly warmer than the room themperature, are two openings 30 and 31 for the suction of air, with exchangeable micro filters (which in need may be cleaned are easy changeable) and exhausting opening 25 with grate 39 through which the warmed air from induction heater come to surrounding space. Automatic thermoregulation of the induction heater is achieved with thermostats Tel and Te2, fixed on the outer sides for the exhaust tubes 34, where thermostat Tel 44, control the work of the fan motor, since it is realized as normally open, and it activates on aproximately 90 °C by which is enabled supply of fan 4 moto until the themperature of the exhaust air fall to 30 °C, whilst the Te2 45, realized as normally closed and turns off when the themperature on the housing of the exhaust tube come up to aproximately 90 °C, switching off the supply of copper windings 32 primary in consequence of which interrupts further increasing of steel cores 33 themperature. Here should be mentioned that heating process continues after that until the core 33 cool down, since the fan 4 does not stop working until the air themperature on the exhaust tube 34 falls to value of aproximately 30 °C. Working principle of device is simply and is effected on the following way: When through the switch 26, breaker 27, copper windings 32, realized on coils 17, 18 and 19, mutually connected into star connection, are energized on R, S and T phase of main voltage supply 3 x 380 V, 50 Hz, in them appears a current making alternating magnetic field which is intersected a cylindrical steel core 33, placed into most narrow chamotte tube 35. Since the steel core 33 is connected to standard yoke 13 made of transformer plates, through the same flows flux, which is functioning under known working principle of complex transformers, so that eddy currents are been created, which cause fast heating of steel core 33 to the themperature of aproximately 350 °C. Warmed steel core 33 transfer the heat to the surrounding air which circulates through three way ventilation passage 5 forced by fan 4. Air flow goes from the first chamotte coil 17 through second 18 till last coil 19 on which through exhaust tube 34 passes out from the housing 1 of heater into surrounding space. There should be mentioned that by such flow of the warmed air after its exit from chamotte coil 17 practically achieve preheating effect which positivelly influence to total decrease of heater energy consumption. It should be noted that on the same principle, like in described working of the subject induction heater, are working monophase and two-phase devices, which may be energized with alternating voltage 380 V, 50 Hz or 220 V, 50 Hz , but in such cases the heating body shall have only one, respectively two cylindrical steel cores 33.

INDUSTRIAL OR OTHER APLLICABLLITY OF THE INVENTION

Realisation of the subject invention is absolutely possible, and its use is recommended for home buildings, small economy objects, green houses and in general there where exist the need for rationing the consumption of electric energy for the heating. Particularly is recommended its use in objects where is used the hot air for example in the drying chambers etc. The subject invention is suitable for mass production and may be produced in the Works manufacturing electrical heating appliances, as well in the specialized good equipped electro workshops on the base of technical documentation which the specialists from the art may design using description and drawings as stated in the present patent application. It should be mentioned that working experiments on the prototype devices of different power which have been manufactured by author of the present invention was successfully effected with extraordinary savings of electric energy. In illustration purposes, economy of the device according to the invention, was compared with thermal storage room heater of designated power 4,5 KW. Thermal storage room heater for one heat storage cycle lasting 8 hours consume 36 KWh of electric energy and induction heater of the same installed power is during the same time period, with intensive blow out of the hot air spent 9,2 KWh of electric energy. Measuring was effected for the both devices with same watthour meter „Iskra" - type T1BY10 - 30 A. Such measuring has shown that difference in consumption of electric energy of induction heater is aproximately four times lesser (where should be notified that in case that measuring of consumption of thermal storage room heater is effected in the working regime where the heat was blowed out, the difference would be significantly higher).

Claims

1. Induction heater, CHARCTERIZED IN THAT, a metal housing (1), cover (2) with handles (42) and (43), three- heating bodies (3), fan (4), three way ventilation passage (5), housing (6) control arrangement (7) and capacitive ^"compensation arrangement (8), where the housing (1) is in form of quadrilateral frame, on which lower end is a metal rectangular bottom (9) with wheels (12), on upper inner side of which are fixed transversaly by ends horizontal foots (10), in the middle of which, preferably by welding, are fixed vertical supporting columns (11), which at its lower end and at its higher end have formed sectional lateral holders (14), in which are inserted ends of the yoke (13), secured by tension screws (15) whilst on their upper side have manipulation handles (16).

2. Induction heater, according to claim 1, CHARCTERIZED IN THAT, a heating body (3) consists of yoke (13) connected with three paralel spaced cylindrical steel cores (33), inserted into chamotte coils (17), (18) and (19) realized as three coaxially placed, mutually separated chamotte tubes (35), (36) and (37) so that form a tubular passages (38), (39) and (40), where around widest chamotte tubes (37) between flange strenghtenings (41) are coiled up a copper windings (32), where ventilation passage (5) consists of fan (4), cylindrical connectors (20) and (21), ventilation passages (22) and (23) and where on the output of the chamotte coil (19) is upper cylindrical connector (24) with exhaust opening (25) and grate (39).

3. Induction heater, according to claims 1 and 2, CHARCTERIZED IN THAT, the control arrangement consists of circuit breaker (27) with collars, switch (26) for turning on of contactor, switch (29) for turning on of fan, electric clock (28), capacitive compensation arrangement (8) made of capacitors CI, C2 and C3 conected into triangle connection, where the automatic thermoregulation has been achived by thermostats Tel (44) and Te2 (45) which are fixed to exhaust tube (34).