My guess as to why not many people make 277 compatible equipment is that for UL safety ratings. The spacing and clearance requirements for line voltage carrying components become larger above 265 VAC.
Larry C
Right. Although it really isn't much more to go from the spacing needed for 240V (NEMA 6-15) to the spacing needed for 277V (NEMA 7-15). Even SOJ cable is rated for 300V. Switch mode power supplies, including those in lots of small wall warts, are safe as high as 240V and are listed as safe for use in places like Europe.
The big reason power supplies are not made in any quantity for 277V is the lack of market. The lack of market exists because 277V is not a domestic or even customary receptacle voltage. You MIGHT have 277V fluorescent lights in the office, but not 277V convenience outlets. If someone has a machine that needs 277V they call an electrician to run a new circuit and install a special outlet for it (assuming 277V is even available in the building).
But, I'm not trying to make computer run directly on 277V. Even if we could convince manufacturers to design them to work and be safe on 277V, flushing out the old ones already integrated in equipment would be years, if not a couple decades.
They do work on 240V. Since +/- 10% is considered an acceptable range, I'm guessing they should be fine on the 244.5V I'd get from the 240+32:240 buck-boost arrangement derived from 277V. That does limit my upper voltage swing to 7.9%. And it might be easier to get the utility to tap their transformers down to deliver around 272V, than to get them to deliver a 416Y/240 service (easy to do with common pole pigs, but for pad mount that would require a special order for three phase, or 3 separate single phase units).
If it turns out the 244.5V is an issue, one fall-back is to go with a 240+48:240 buck-boost arrangement, which would step 277V down to 231V. That would change the buck-boost capacity ratio from 7.5 down to just 6.
