Concentric Induction Heating for Dismantlable Adhesion Method

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1 Concentic Induction Heating fo Dismantlable Adhesion Method Keywods «Induction heating», «Inteio constuction», «High fequency invete», «Allove method», «Dismantleable adhesion» Abstact A dismantlable (=dismantle-able) adhesion method using electomagnetic induction heating (IH) and themoplastic adhesive has been poposed. The featue of this method is easily able to bond and dismantle in many times. In conventional inteio woks, a cicle type induction coil is applied. But this coil is ineffective fo concentic heating and deep distance heating to load metal. So due to effective adhesion depend on induction heating (IH), we cay an expeiment on the new concentic coil with feite coe because it geneates many magnetic fluxes to load metal at deep distance. In the study, a single-phase concentic coil using U-shape feite coe is poposed. Its expeiments and analysis fo induction heating (IH) and the electic chaacteistics ae discussed in this pape, and the usefulness of poposed coil is poved. Intoduction As shown Fig.1, in inteio constuctions, fo example, gluing woks of floo panels, tiles and cokboads etc, a novel dismantleable adhesion method using induction heating (IH) and themoplastic adhesive was named as the Allove method [1]-[5]. The gluing and dismantle of inteio mateials ae opeated by melting of themoplastic adhesive depend on themal enegy with induction heating (IH). Theefoe the method is usefulness fo easy bonding and dismantlement with no damage of mateials in many times. As the examples of paied poducts of glued mateial and heating metal, a tile o cokboad pasted a thin galvanized steel plate to its behind ae shown in Fig.2. The poducts have been applied in many facilities as shown in Fig.3. The woking time was shoted in compaison with conventional inteio woks. And the method is convenient in daily woks of woke, because of no vibation and noise in woks. In geneally, the suface of steel plate is coated with a themoplastic adhesive which is melted by induction heating (IH). In usually, the load metal is heated by conventional cicle type coil [5]. But this coil is ineffective fo concentic heating and deep distance heating [4], [5]. Fo the pefect heating to above taget steel using induction heating (IH), we popose a new induction coil using U-shape feite coe. U-shape Coli fo Concentic Heating Fo the effective heating by induction coil, it is vey impotant the stong magneto-motive foce (MMF), low magnetic impedance and high elative magnetic pemeability. Because heating enegy becomes bigge to the squae of the MMF. And the low magnetic impedance and high elative magnetic pemeability incease magnetic flux in the load metals. So, it is bette to be made of magnetism steel plate fo a load. Fig.4(a) shows the tial coil wound by Litz wie to U-shape feite coe and the magnetism steel plate fo heating taget. In the figue, most of magnetic flux will pass in

2 the feite coe and steel plate because of the high pemeability. Thus, the geat majoity of magnetic flux path in the tial coil is shote than the case of conventional cicle coil, because each coe head ae opposite to load metal. It is mean of low magnetic impedance. And also the distance between coe head and load metal is stongly affected fo effective induction heating (IH). Consequently, the coil wound to U-shape coe is able to geneate a lage magnetic flux and eddy cuent on the steel plate. Thus the eddy cuent in the load is concentated between the coe heads, because most of eddy cuent is induced aound the coe head. Fig. 1: Pinciple of the Allove method. Fig. 2: Paied poducts of glued mateial and heating metal. Fig. 3: Bonding woks. (a) Setting of tial coil and load steel plate. (b) Size of coil and U-shape feite coe. Fig. 4: Tial coil and load metal.

3 Specification of U-shape coil and load metal Fig.4(b) shows the measuement of induction coil with feite coe. The elative magnetic pemeability of coe is The induction coil is applied a Litz wie fo flow a high fequency cuent. The coil s numbe of tun is 40 and impedance is ( ) at 20 (khz). And the applied invete has a capability of 200 (V) and 20 (A) at 20 (khz). The load impedance included coil is adjusted about 10( ), because of the maximum capability of invete. So, as shown Fig.5, the seies capacito poduced the esonance at 20(kHz) is connected. The capacitance of capacito is (nf). Fig.6 shows the measuement of the analyzed steel plate as a load metal. That is: Length: 300 (mm) Width: 60 (mm) Thickness: (mm) and elative magnetic pemeability: 150. Incidentally the steel plate applied in Fig.2 is a same thickness plate. Fig.5: Seies esonance cicuit. Fig.6: Heating taget s steel plate. Heating analysis by FEM simulation It is able to inspect above electomagnetic-heat conductivity phenomenon using compute simulation with finite element method (FEM). We pefom the 3D simulation using ANSYS Ve (Academic Teaching Intoductoy) [6]. But, the maximum elements and nodes of the pogam ae limited as a 32,000. Although we d like to ty 1/1 model of Fig.4 in the simulation, it is impossible by ove elements and nodes. Theefoe, the following simulation is pefomed with half model in Fig.4 (b), because magnetic flux and eddy cuent on the steel plate ae symmety to the cental cossing line. Fom the limited elements, the divided element size in the steel plate become to 5(mm). Edge elements ae also used in the simulation. Thus the pecision of analysis isn t a compaative poo [6]. As the esults of FEM simulation, Fig.7 shows the contou distibution of magnetic flux. The concentated flux between the both coe heads is confimed. Fig.8 shows the eddy cuent vectos on steel plate. Colo vectos fom ed to blue ae shown eddy cuent density fom high to low. In this figue, cuent flowing aea with colo vecto is shown only a half aea of steel plate with the compute simulation. In pactical, symmetical colo vectos should be added in dotted aea. The heating enegy of the steel plate in each segment is means of the calculated powe loss with eddy cuent in each element. Fig.9 shows the distibution of heating enegy in the steel plate. Colos fom ed to blue ae tempeatues fom high to low. At the edges of steel plate, the highest tempeatue depend on concentated cuent is obseved. Theefoe the steel plate size should be sufficiently lage than coe size, because the edges of the metal might be oveheated and buned by concentated cuent. So in the subsequent expeiment, we d like to exchange a heating metal to the width steel plate applying tile and flooboad. That is, the width of steel plate is 212(mm), and othe measuements ae same as Fig.6. Heating Expeiment by U-shape Coil In pactical inteio woks of bonding o dismantlement, it is impotant an investigation on heating chaacteistics of actual thin steel plate as heating taget. Theefoe, an expeiment of heating to the steel plate is pefomed by tial coil. Expeiment condition In the expeiments, the gap is vey impotant paamete fo heating. The gap is means of a thickness of inteio mateials, but it is expeimented only spacing because of the vaious heat conductivity of

4 mateials. So we disegad thei mateial popety. That is, the gap expess a distance between the coil and steel plate, and is set fom 3 (mm) to 21 (mm) at evey 3 (mm) in the expeiments. The expeiments and analysis of electic chaacteistics ae pefomed with constant coil cuent, because of having none linea heating chaacteistics with induction heating (IH). By adjusting invete output voltage, the constant coil cuent I 1 is held in 10 (A, ms). Then coil input voltage E (V, ms), input powe W (Watt) and powe facto PF (%) ae measued by digital multi-mete. Themal distibution on the steel plate is obseved with themo-gaph and tempeatue in maximum heating point on the steel plate is gauged by themocouple. It is cente of both coe heads as shown in Fig.10. The figue shows in the case of gap: 3 (mm), heating time: 4 (sec), aived tempeatue in cente : 200 ( ). A consideation of skin effect is impotant because of high fequency cuent. So the about 90 (%) of heating enegy depend on eddy cuents is consumed in thickness fom suface of the steel plate [7]. When the thickness of steel plate is nealy equal to (skin depth), the calculated invete fequency to consume 90 (%) of heating enegy is deduced unde 21.7 (khz) fom Eq.(1) ( m) ( mm ) (1) 2 f f f whee :esistivity, : elative magnetic pemeability, f : fequency. And the paametes of the steel plate ae =0.115 (mm), =150, = ( m). Thus the invete fequency is decided as 20 (khz). And the themocouple is set on the evese side of the steel plate fom view of the coil side. Fig. 7: Contou of magnetic flux aound coil by FEM simulation. (Colo ba shows magnetic flux density) Fig. 8: Eddy cuent vectos in steel plate by FEM simulation. (gap: 3(mm) and coil cuent: 10(A,ms)) Fig. 9: Rising tempeatues by heating enegy in steel plate. (gap: 3mm and coil cuent: 10(A,ms)) Heating Chaacteistics of Steel Plate Gap is most impotant paamete fo decision of suitable heating time. When gap inceases, the heating time is also inceased. The magneto motive foce (MMF) depend on coil cuent is also concened with heating time and the coil cuent. In this coil, the cuent is limited about 10 (A,ms)

5 constant. The limit of the cuent is detemined by the cuent capacity of using Litz wie. If it is possible to apply 20 (A), heating time becomes to quate because MMF is double. Fig.10 shows a themal distibution on the steel plate which is obseved by themo-gaph. In Fig.10, the maximum tempeatue point is cente of coe heads and it becomes 200( ). Thus the U-shape coil is effective fo concentic heating. Fig.11 shows the tansient heating chaacteistics with gap paamete. And Fig.12 shows the elationship between gap and heating time at a melting tempeatue of one s adhesive. These chaacteistics ae pactical usefulness in field bonding woks. Fig. 10: Themal distibution on steel plate. Fig. 11: Tansient heating chaacteisitics with gap paamete. Fig. 12: Gap vs. heating time with melting tempeatue of adhesives. Electical Analysis of U-shape Coil In this section, tial coil and thin steel plate as load ae defined as a pimay coil and a seconday load espectively. At fist, a no-load expeiment that is mean of nothing the steel plate is pefomed. No-load expeiment Fo a no-load expeiment, an adjusted cuent 10(A, ms) at 20 (khz) is supplied to the pimay coil in the condition of emoved seconday load. In this expeiment, measued E, I, PF and W change the symbols to E 1, I 1, PF 1 and W 1 fo distinction them fom data of load expeiment. Fom no-load data, the coil s coppe loss W R1 and esistance R 1 ae calculated by Eq. (2)-(3). Whee the coe s ion loss W i in Eq. (2) and its esistance R i in Eq.(4) ae deduced by efeence of coe s data [8] of magnetic flux density B vs. powe loss and Eq.(4)-(5). Consequently, fom measued data E 1 =434 (V), I 1 =10.06 (A), PF 1 =1.38 (%) and W 1 =60.6 (W), R 1 and R i ae deduced 0.58 ( ) and 12 (m ). W1 W i WR1 (2) WR 1 R1 (3) 2 I1 Wi Ri (4) 2 I 1 E1 B 2 f N S Whee B: magnetic flux density, N : 40 (numbe of coil tun), S : 625 (mm 2, coss section of coe). Load expeiment Load expeiment is put the steel plate as seconday. It is pefomed with gap paamete unde the constant 10 (A, ms) and 20 (khz) of invete. So, the symbol of coil cuent I 1 also changes to the same value I 2. In this time, measued paametes change to E 2, I 2, PF 2 and W 2 too. W 2 is able to (5)