It appears as though the minimum recommended generator size is 6kVA. This size would allow the use of 'brushless' generators (poor voltage regulation & poor output waveform).
See the below image, which comes from http://apac.thermadyne.com/IM-Upload...29%20Final.pdf
“I do not think there is any thrill that can go through the human heart like that felt by the inventor as he sees some creation of the brain unfolding to success... Such emotions make a man forget food, sleep, friends, love, everything.” - Nikola Tesla.