b dielectric heating for this purpose the outputs of the medium voltage supply module b supply higher voltages than the basic supply module b a respective one of the silicon rods or thin silicon rods r 1 r 2 r 3 r 4 is connected at each of the outputs preferably the medium voltage provided at the outputs has also a higher frequency of for example 5 khz than the mains frequency the medium voltage supply module mv shown in fig1 has a total of three converters 20 which can be used to generate from a three phase mains voltage a voltage with higher frequency this voltage is then upconverted by the transformers 21 to a higher voltage of for example up to 12 kv this medium voltage which has a higher frequency than the mains voltage is then supplied at the outputs of the medium voltage supply module mv a respective one of the silicon rods or thin silicon rods r 1 r 2 r 3 r 4 is connected at each of the outputs the outputs 23 of the medium voltage supply module mv are linked with one another for this reason only five terminals 231 to 235 are provided for the illustrated four outputs of these five terminals the terminals 232.