Iran:2nd International Conference TPE-2004Electrical Engineering DepartmentAzarbaijan University of Tarbiat MoallemTabriz, Islamic Republic of IranP.D.Box: 53714-161Tel.:(+ 98412) 4524982, 4325146-8 (ext. 2100)Fax: (+ 98412) 4322594E-mail: n.m.tabatabaei@dr.comURL: http://www.azaruniv.edu

Azerbaijan:2nd International Conference TPE-2004H. Javid pr.{ 33 Institute of PhysicsAzerbaijan National Academy of SciencesAZ 1143{ Baku - 143, Republic ofAzerbaijanTel.: (+ 99 412) 393263{ 394161Fax: (+99412)395961E-mail: arif@physics.ab.azURl: http://www.ab.az

Turkey:2nd International Conference TPE-2004Electrical and Electronics DepartmentFaculty of Engineering and Architecture{ GaziUniversity06570{ Maltepe{ Ankara{ Republic of TurkeyTel.: (+90312) 2311340,2317400 (ext.2331 or 2315)Fax: (+90 312) 2308434E-mail: t9RjiJm~~QfL~Q1!lr:.i[~~@giJfL~_(t\J..trURL: b1!JJ:JLwww.mmf.gazLedu.tr/elektrik

Date: June 30, 2004

Dear Dr. (s) Halil Murat Unver, M. Timur Aydemirunver@kku.edu.tr { aydemirmt@gazi.edu.tr

We are pleased to inform you that your submitted paper entitled "A Simple Inductionheatingdesign forthe Steel Molds of Aluminum Extrusion Presses" has been accepted for oral presentation at the SecondInternational Conference on "Technical and Physical Problems in Power Engineering" (TPE-2004).

The TPE-2004 Conference is organized by Azarbaijan University of Tal'biat Moallem (Tabriz, IslamicRepublic of Iran), Institute of Physics of Azerbaijan National Academy of Sciences (Baku, The Republicof Azerbaijan) and Cazi University (Ankara, The Republic of Turkey) that will be held on September6-8, 2004 in Tabriz, Trail.

Please kindly complete the Registration form on the conference website www.tpe-conf.com and informus about attendance progl'am in the conference bye-mail addresstpe2004@tpe-conf.com .

Your attendance and presentation is important for the Conference. Please notify the Secretariat if forany reason you are unable to attend at the Conference and give your paper.

Dr. Mohammad AghazadehDO' {PI! O'vi,J.

Al'l~'/TPE-2004 Chairman and President ofAzarbaijan University of Tarbiat MoallemTabriz, Islamic Republic of Iran

mailto:n.m.tabatabaei@dr.comhttp://www.azaruniv.edumailto:arif@physics.ab.azhttp://www.ab.azhttp://b1!JJ:JLwww.mmf.gazLedu.tr/elektrikmailto:unver@kku.edu.trmailto:aydemirmt@gazi.edu.trhttp://www.tpe-conf.commailto:addresstpe2004@tpe-conf.com

2nd International Conference onTechnical and Physical Problems

in Power Engineering

TABRIZ - IRAN

No: 14

AzMEAFI

AzETEELI

A SIMPLE INDUCTION HEATING DESIGN FOR THE STEEL MOLDS OFALUMINUM EXTRUSION PRESSES

Department ojElectrical and Electronics Engineering, Kirikkale University. Kirikkale, Turkey*Department of Electrical and Electronics Engineering, Gazi University, Ankara, Turkey

unver@kku.edu.fr, aydeminnf@gaziedufr

Abstract- Induction heating is a widely preferred method forheating metals. However, its initial investment can be costly forsimple processes. In this work. an affordable heating system hasbeen developed for use in induction heating. Steel molds used inaluminum extrusion presses can be heated up to the extrusiontemperatures by using this system.

I. INTRODUCTIONInduction heating is used in several applications such asmelting, annealing, welding, shrink fitting and plasma.The heat energy obtained in induction heating is given as

Power supplies intended for this application has toprovide the necessary power, frequency and physicalconditions. Investment cost of these power supplies ishigh, and therefore, for simple applications theseinduction heating systems are not preferred.Heating the steel molds used in aluminum extrusionpresses is one of these simple applications. These moldsare preheated up to the press temperature (450 - 500 °Clfor approximately 30 minutes in resistive ovens. Thisprocess has to be repeated every morning when startingthe first press and anytime when a new mold is placed.Since the mold hardness may deteriorate, it is not properto keep the molds in these ovens for prolonged periods.Heating period may be considered as a lost time.Moreover, the energy loss is higher since the efficiency ofresistive ovens is less than that of the induction ovenS.There have been some work in wh ich a metal strip washeated by using a coil placed on a yoke or inside in a packof laminated steel (magnetic yoke.) Medium frequencyhas been used in these applications, and temperatures ashigh as 900°C have been reached on aluminum and steelwork pieces [1-4].This work suggest a simple and cheap system utilizing thebasic principles of induction heating to quickly heat thesteel molds used in aluminum extrusion presses. Lowpower consumption is also aimed.

II. METHODFigure I shows the system designed for the heatingprocess. It is connected to three-phase 50 Hz power grid.The 3-phase power transformer is rated 150 kVa, and hasseveral taps. The balance inductor also has a tappedstructure. There are also a balance capacitor and areSOnance capacitor in the system. A II the components areconnected on the secondary of the transformer in delta.Component values are given as follows so that balance isachieved: Balance inductor, 11.74 mH, balance capacitor863 ~lF, heating inductor 2.66 mH, resonance capacitor3795 ~lF. The 3rd terminal of the 13-tap transformer isused. The no-load voltage at this terminal is measured tobe 160 V.The winding is made by using a 15x 17 mm cross-sectionconductor and it has 2x 15 turns. This coil is placedaround a core with a cross-section of 140x200 mm. Thearm height is 300 mm, and the window opening is 110mm. Two yokes with a cross-section of 140x200 mm areat the top, and the mold is placed between these twoyokes. The inductor design is pictured in Figure 2.The parameters for the balance inductor are as follows:core cross-section= 120x 170 mm, ann height= 3 I0 mm,window opening= 80 mm. There are two windings with34 turns of lOx I0 mm conductor On each one.

:-:--:n,,,,,,III. EXPERIMENTAL RESULTS

Experiments aiming to reach to 450-500 °C in 120seconds were performed. Figure 3 shows some data andwaveforms related to the heating section. Figure 3a showsthe voltage and current variations of the heating inductor

mailto:unver@kku.edu.fr,

for 120 seconds. Mold temperature was measured to beto=20 °C at the beginning of the experiment, and t120=470°C at the end.

'~"'oke: mold

\ !•

Balance inductor and balance capacitor currents weremeasured to be Ib=44.57 A and [c= 44.20 A, respectively,while the heating inductor current was 66.1 A at 158.1 V,as seen in Figure 3b. Therefore, the apparent power is

Since the power factor was PF=0.87 as seen in Figure 3c,the active power can be calculated as

The displacement factor during this operation is measuredto be Cos

As the minimum power required by the heater is 7.06 kW,the minimum efficiency for the total power transfer canbe found as

'7 = 7,06 xlOO = 64.98%10,87

Since the maximum efficiency for the medium frequencyinduction steel annealing and melting ovens is 60%, it isobvious that a considerably better value of efficiency isobtained with the developed system.Table I gives the current and harmonic values for eachphase. It is clear from the table that, the currents aredistributed to each phase very evenly although the line-to-line voltages are not balanced.

0.66PF0.93 C05.SUOH2

FUHOAMEHTAl

._----.--_ .._--_ ..__ .-------~_._.-/0.. _ .~l • : !....~.~~

:--'::·~v~-·A/·y-·_X\v-..~•.-.r/L~~~~\.rf~·~.-~~~~~~~:.... - ... :

0.74PF0.76 C05.49.9112

fUHOAMEHTl1L

Figure 4 Power drawn by each phase: (a) Phase R. (b) Phase S. (e)Phase T

IV. CONCLUSIONA simple and low cost system to heat the steel molds forthe aluminum extrusion presses was developed. Thetemperature was increased to 470°C in 120 seconds. Apicture showing the heating set-up is given in Figure 5.The temperature that is read on the instrument wasobtained in 160 seconds.The efficiencies of the heating unit and the total systemwere obtained as 77.69% and 64.98%, respectively. Thisis better than the maximum value of 60% for mediumfrequency induction steel annealing and melting oven.The current harmonics exist at the 3rd and 5thfrequencies, but since the total power drawn from the lineis 10.87 kW. their effect on the supply is not important.

1" "," 51h 7thJ

50 Hz 150 Hz 250 Hz 350 Hz

THO 48.3 %r 22.30 A 5.04 A 14.52 A 103 A2561 A 83.2 %r 18.3 %r 522 %r 3.5°.lor

KF 63 00 -1690 21 0 1570

I Sl 3rd 5th th50 Hz 150 Hz 250 Hz 350 Hz

THO 72.1 %r 17.83 A 6.14 A 17.38 A 0.99 A25.74 A 69.5 %r 24.3 %r 67.6%r 3.7%rKF 12.7 00 -1360 -1240 -1480

I" .••rd 5th thJ50l-lz 150 Hz 250 Hz 350l-lz

THO 205 %r 2964 A 1.97 A 556 A 056 A30.28 A 98.0 %r 6.5%r 183 %r 1.9%rKF 2.1 00 620 850 180

(b)Figure 5. Pictures orlhe healing unit

REFERENCES[I)S. Fukushima, K. Okamura, T. Krase, G. Prost, "A

High-Performance Edge Heater for the Hot StripMill", IEEE Transactions on Industry Appl., Vol 29,No.5, Sep/Oct 1993.

[2)C. Guaneri, P. Masse, Y. Ten'ail, "ExperimentalThermal Validation of Two Vector PotentialFormulations in Industrial Transverse Flux InductionHeating Process", IEEE Transactions on Magnetics,Vo131, No, 3, May 1995.

[3]K. Tani, T. Yamada, " ew Approach to CoupledMagnetic and Thermal Problem in Induction HeatingSystem with Traveling Conducting Plate Using CubicInterpolated Pseudo-Particle Method", IEEETransactions on Magnetics, Vol 33, No.2, March1997.

[4]N. Bianchi, F. Dughicro, "Optimal Design TechniquesApplied to Transverse - Flux Induction HeatingSystems", IEEE Transactions on Magnetics, Vol. 31,No.3, May 1995.