It is odd that Siemens seems to only offer single phase stoves in Sweden. And I don't see why anyone would want to buy a model, that needs to be modified in a way that the maker has not specified, and it would still not work on full power.
Darn it. They have - or had an equivalent model which draws 10,9 kW http://www.siemens-home.bsh-group.com/se/produktlista/HC748233U#/tab=section-technicalspecs, but was discontinued and replaced by the model I want. 
That is probably because the older model did non regulate the power consumption, so that it blew fuses.