Data from measurements on the first Powerformer generator installed in Porjus, Sweden, will be-presented. The generator has a rating of 45 kV and 11 MVA. In total, the machine has been running more than 13700 h (October 2001) and has been exposed to a number of different tests including short-circuit tests on the terminal at 100% magnetization. Experience and some results from these short-circuit tests will be presented. Also, the response on the auxiliary winding during a short circuit on the main winding will be shown.