Prof. Dr.-Ing. Bernard Nacke Institute of Electrotechnology Leibniz University of Hanover (Germany)

Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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1. Principle of induction heating 2. Advantages of induction heating and typical applications 3. Mathematical equations 4. Skin effect, proximity effect 5. Influence of frequency and electromagnetic penetration depth on induced power 6. Influence of material, non-linear material properties 7. Influence of work-piece geometry 2

Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

Magnetic flux / induction effect

Induced current

Quelle: RWE-Information Induktive Erwärmung Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Principle of induction heating

Heating of a steel tube

Quelle: RWE-Information Induktive Erwärmung

Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Heat generation without flame (variable atmosphere, vacuum) High power densities High process temperatures High heating-up speeds Direct heating within the work-piece High thermal efficiencies Excellent control of induced power Many chances for new technologies using induction 5

Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

Classical applications

Melting of metals in induction furnaces

(foundries, metal plants)

Heating of metals for deforming (forging, rolling) Heat treatment of metals like hardening and annealing Welding of steel tubes

Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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New applications

Heating of metallic strips and sheets (longitudinal field, transverse field)

Thixoforming, thixocasting Melting in cold crucible Stirring of metallic melts before solidification Electromagnetic processing of semiconductor melts for the production of semiconductor wafers and solar cells

Skull melting of oxides and glasses Combined induction pre or post heating and laser welding Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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The flow field can be described by the Navier-Stokes equation

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Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Current density distribution in a cylindrical work-piece (approximation) Electromagnetic penetration depth

The exponential distribution of current and magnetic field is exactly valid only for plane surfaces (approximately valid for cylinders for d/δ > 4) Quelle: RWE-Information Induktive Erwärmung Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Quelle: RWE-Information Induktive Erwärmung Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Quelle: RWE-Information Induktive Erwärmung Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Inductor efficiency of a cylindrical arrangement of inductor and work-piece as function of work-piece diameter to penetration depth ratio Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Induced power density dependent on the ratio of d/δ for constant frequency and variation of the work-piece diameter Prof. Dr.-Ing. B. Nacke / Institute of Electrotechnology, Leibniz University of Hannover

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Quelle: RWE-Information Induktive Erwärmung Prof. Dr.-Ing. B....