Several problems of melting in the induction crucible furnaces are described. A short description of ICF ELTA program for simulation of electromagnetic and

thermal parameters in these systems is given. The program was used at the initial stage of the development of new technological processes and the induction

crucible furnaces. Preliminary results allowed to find a rational decision of an induction system, the required parameters of a refractory and a power supply. Non-

conductive and graphite crucibles of the furnace were compared from electrical and economical points of view.

Introduction

A preliminary investigation of the melting processes in the induction crucible furnaces was carried out

using ICF ELTA. The results of simulation permitted to find the required geometrical parameters of the

induction coils, the refractory and the electrical parameters of the power supply for the new

technological process. The advantage of the graphite crucible from an economical point of view was

proved.

Future information may be found at: www.nsgsoft.com.

Conclusion

Introduction

Preliminary investigation of metal melting in ICF ELTAV. Bukanin¹, A. Ivanov¹, A. Zenkov¹

¹St. Petersburg Electrotechnical University (LETI), 5, Prof. Popov Str., St. Petersburg, Russia, 197376

where Q, P – elements of system, zQ – impedance of coil, xQP – reactance,

I – current of element, U – voltage of coil, NQP – coefficient of Magnetization

Forces, W – number of turns, SQ = µQ /(1 – µQ) – coefficient, µQ – magnetic

permeability

Description of ICF ELTA: Calculation methods

ICF ELTA program provides a two dimensional calculation of electromagnetic and

thermal fields in cylindrical induction system using both integral and differential

numerical methods

where R – radius, – resistivity, – angular frequency, µµ0 – magnetic permeability. Cv – specific heat, t – time, λ – thermal conductivity, Z – axial coordinate, w – volumetric power density

The ICF of 10 tons steel with 2 parallel connected 8 windings coils and 2 Faradayrings was described in [5]. Frequency of power supply is 286 Hz.

Results of Simulation: Comparison of results

, ;

, 0;

, 0 ;

, 0

Q Q QP P Q

P

k Q Q QP P

P

f Q QP P P

P

Q Q QP P P

P

Q B Z I j x I U

Q N Z I j x I

Q N I N W I

Q F S I N W I

B

1

1

( ) ( ) ( )

( ) ( ) ( ) ( ) 0

0( ) ( ) ( ) ( )

0( ) ( ) ( ) (( ( ))

Bk Bf BF B B

kkB kk kk kf kF

ffB B fk ff fF

FB B Fk Ff FF F

Z j x j x j x I U

Ij x Z jx j x j x

IN W N N N

N W N N N S I

Three types of crucible for coreless induction crucible furnaces are known

• crucibles with non-conductive refractory;• conductive crucible;• cold crucible.

Main equations for internal electromagnetic (Н) and temperature (T) fields

HjR

HR

RR

0ωμμρ

1

)(

wZ

T

Z

T

R

TR

R

T

Rt

TCv

)( )( λλ

1

Description of ICF ELTA:Main features of the program

ICF ELTA program has been developed by induction specialists to preliminary

simulation of induction melting technologies and equipment

• short time of calculation

• selection of required compensating circuits and

leads

• convenient preprocessing for input parameters

• convenient post processing for visualization of

output parameters

Preprocessing

Postrocessing

References[1] Mühlbauer, A. (2008). History of Induction Heating and Melting. Vulkan-Verlag, Essen., 202.

[2] Muelbauer, A., Raming, A, Muiznieks, A, Vogt, M, Bernier, F, Choudhury, A, Jarczyk, G. (1998). Induction melting of metallic high-temperature alloys and oxides

in a cold crucible. In: Proc. of the International Induction Heating Seminar, Padua, May 13-15. 271-278.

[3] Ernst, R., Garnier, C., Petitpas, P., Trassy, C. (2007). 2D and 3D numerical modeling of a cold crucible for Induction melting of metallic high-temperature alloys

and oxides in a cold crucible. In: Proc. of the International Symposium Heating by Electromagnetic Sources, Padua, June 19-22. 33-40.

[4] Umbrasko, A., Baake, E., Nacke, B., Jakovics, A. (2007). Numerical studies of the melting processes in the induction furnace with cold crucible. In: Proc. of the

International Symposium Heating by Electromagnetic Sources, Padua, June 19-22. 277-284.

[5] Nemkov, V. (2013). Magnetic flux control in induction installations. In: Proc. of the international conference HES-13 Heating by Electromagnetic Sources,

Padua, May 21-24. 117-125.

[6] Demidovich, V., Pozniak, I., Baake, E., Muelbauer, A. (1998). Methods and tools for simulation and design of induction crucible furnaces. In: Proc. of the

international Induction Heating Seminar, Padua, May 13-15. 389-396.

[7] Nemkov, V.S., Demidovich, V.B. (1988). Theory and Calculation of Induction Heating Devices. Energoatomizdat, Leningrad, 280. (in Russian).

Pind [kW] Pind [kW] Iind [A] Pwork [kW] Qind [kVAr] ind

ICF ELTA 902 5000 24550 4098 53860 0.819

FLUX 2D 850 5000 24040 4110 47800 0.822

Comparison of some obtained results showed a good practical correlation betweenan experiment and calculation.

Results of Simulation: Melting of copper and aluminum in graphite crucibles

Graphite crucible can increase electricalefficiency of heating. The rational solution forthis configuration is graphite crucible atfrequency 8000 Hz.

Coil•29 cm interior dia;•50 cm length;•9 turns;•rectangle tube profile4×3×0.9 cm

Generator•250 kW output max.;•Frequency: available range is 50; 250; 500; 1000; 2400; 8000; 10000 Hz;

Crucible: height 55 cm, external dia. 46 cm, internal dia. 34 cm. Magnesite refractory: thickness 6 cm – wall, 15 cm – bottom. Coil: 47 cm ID, 37 cm length, 10 number of turns, rectangle tube: 3.2×3.2×0.4 cm. Melt: height 37 cm, diameter 34 cm.Power supply: thyristor inverter 800 V, 800 kW, 500 Hz. Constant inductor power 600 kW.

Variant of crucible t, [s] Avg. η

Specific W, Copper/Total

[kW·h/t]

Product. [t/h]

Mean T, [C]

Non-conductive, cold start

1515 0.316 265/845 0.712 1200

hot start 1125 0.342 213/628 0.959 1200

Graphite, cold start 940 0.592 309/525 1.15 1200

hot start 630 0.606 212/352 1.71 1200