Power system for supplying high voltage to an electron beam emitter, which is adapted to sterilize a packaging container or a packaging material by electron beam irradiation, the power system comprising a voltage multiplier for generating a high voltage, a first voltage measurement device for measuring an output voltage level of the voltage multiplier and providing a first measured voltage value, and an actuator for modifying the output voltage level of the voltage multiplier based on the first measured voltage value provided by the first voltage measurement device, characterized in that the power system further comprises a second voltage measurement device adapted to independently measure the output voltage level of the voltage multiplier and provide a second measured voltage value.