Importance

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Abstract

A coreless induction furnace includes a vertical melting crucible defining a melting chamber having upper and lower chamber portions and at least two coils. A first one of the coils is disposed so as to surround the upper chamber portion and a second one of said coils is disposed so as to surround the lower chamber portion. The furnace also includes a single-phase load-commutated oscillation circuit converter, a plurality of capacitors and an electrical circuit system electrically connecting the coils, the capacitors and the converter. The electrical interconnection is such that the first one of the coils is electrically connected in series with a first one of the capacitors having a first capacitvie impedance to thereby present a first oscillation circuit, and the second one of the coils is electrically connected in series with a second one of the capacitors having a second capacitive impedance to thereby present a second oscillation circuit. The electrical interconnection is also such that the converter, the first oscillation circuit, the second oscillation circuit and a third one of the capacitors having a third captive impedance are all connected in parallel relative to one another. In one aspect of the disclosure, the capacitive impedance of at least one of the first and second capacitors may be selectively varied. In another aspect of the disclosure, the furnace may include an on-off switch connected in series with at least one of the first and second coils.

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First Claim