What RedOctobyr says is correct, you have a 3 phase generator with a delta connection. It has three coils connected in such way that they form a triangle, from each vertex, a line is taken to connect one pole of the 3 phase connector. From each coil ends two lines are connected to each single phase outlet . There are 240 VAC between each pair of lines, but they are not in phase, it means that between each pair of lines an AC voltage appears, reaching its minimum and maximum values at distint times, so at anytime a voltage difference will be present between lines, this is the reason because it is not possible to joint two lines in a three phase system. Please see the attached diagram.
Last edited by Osviur; 06-24-2019 at 11:18 AM.