Patent ID: 7910865

Claim:
A method for supplying power to a plurality of induction coils in an induction apparatus, each said induction coil having a respective frequency converter and being supplied with said power by means of said respective frequency converter operating at a given frequency, wherein during simultaneous operation of the plurality of said induction coils, said frequencies of said frequency converters are set as a function of said power provided with respect to a frequency difference between said frequencies according to one of the following operating modes: a) said frequency difference is zero, b) said frequency difference is less than 1 kHz, or c) said frequency difference is between 15 kHz and 25 kHz, and wherein at a start of operation a first induction coil and a second induction coil are operated: a) with said first induction and said second induction coil both starting at a first common frequency and decreasing from the first common frequency to a second common frequency wherein at said second common frequency operation results in: 1) a first power provided to said first induction coil that is greater than a subsequently provided first average power provided to said first induction coil, and 2) a second power provided to said second induction coil that is less than a subsequently provided second average second power provided to said second induction coil; b) wherein subsequent to reaching said second common frequency, said induction coils are operated: 1) during a first time period wherein said first power of said first induction coil decreases to a level less than said first average power, and said second power of said second induction coil increases to a level greater than said second average power, and 2) during a second time period wherein said first power of said first induction coil increases to a level above said first average power, and said second power of said second induction coil decreases to a level less than said second average power.