Abstract: An inductive welding device includes a circuit for the inductive heating of a metal that is embedded in a non-magnetic bed. A transformer induces eddy currents in the metal as a function of an exciter current and an exciter voltage and forms a load impedance together with the metal to be heated. Temperature monitoring is provided for the metal to be heated. The load impedance is operated in the region of the resonant frequency of the load impedance. The exciter current and exciter voltage and their phase shift relative to each other are measured and logged when the metal is heated. A temperature progression which is proportional to the phase shift is calculated from the exciter current, exciter voltage, and phase shift.

Abstract: The invention relates to a circuit for the inductive heating of a metal that is optionally embedded in a non-magnetic bed by means of a transformer. The transformer induces eddy currents in the metal as a function of an exciter current IL and an exciter voltage UL and forms a load impedance XL together with the metal to be heated. Moreover, temperature monitoring is provided for the metal to be heated. In order to provide advantageous monitoring conditions it is proposed that the load impedance XL is preferably operated in the region of the resonant frequency thereof, the exciter current IL and exciter voltage UL and their phase shift ?? relative to each other are measured and logged when the metal is heated, and a temperature progression which is proportional to the phase shift ?? is calculated from the exciter current IL, exciter voltage UL and phase shift ??.