I went out to an steel whole seller plant. In the yard they have a huge crane that moves and loads steel. which is being fed by #2AWG from a 225Amp three phase breaker. Next to that panel they have another panel with a 20Amp/3 phase breaker that powers 277Volt lighting. When i opened both panels i did not see a grounded(neutral) conductor. The way they are getting the 277 from 480 is they are using the grounding in this case the frame of the panel.
The reason i know it is the neutral because there are three colored conductors and one grounded(neutral) going to the lighting fixtures. Besides there are photo cells that control the lighting fixtures which are rated for 277 and have a neutral conductor.