This would be useful

[SpliphHendrix]

I would like to find an economical way to transform 277 into 240 without wasting wattage. This will be line to neutral voltage. I’m planning on using it on 800 plus outlets at 4000 watts (continuous load) 3250 is the normal wattage. I found a converter for 69$ and that would be way less than the 200k+ in transformer cost as well as surge protection but the outlet itself is split and it’s a huge box as well. I don’t want to waste energy with resistors either. I’ve been trying to solve this all night and I’m down to 10 volts difference but it’s nominal and I would like to have protection as well as regulation in place. A small battery and led would be awesome if I could convert and invert back. Anyone have any ideas? Feel free to message me or post publicly. This is just one of many projects I’ll be completing within the next few weeks, one way or another

 

[Nigel Goodwin]

You need transformers, large and expensive - as simple as that. Anything else is just going to be something crap pretending to be a transformer, and making a poor (and unreliable) job of it.

However, as usual in these kinds of posts, there's no context - why you have you got such a stupid voltage?.

 

[rjenkinsgb]

277V L to N is from one of the common USA three phase supplies - 480V line-to-line voltage.

Transformers are the only efficient way to do it; auto transformers are cheaper and more efficient than isolating.

Or, 2:1 using line to line input gives 240 out.

For that quantity, custom wound transformers may be economical.

Or just put in a substation transformer to feed the whole system - a normal US "120V System" style with 120-0-120 output would be perfect.

Again, if necessary, have some large ones custom wound for the job.
eg. 480V three phase primary autos with 240V output taps and neutral connected star point, say 80 - 160 KVA each, to run multiple outlets.

They would be big, 3ft x 3ft x 2ft at a guess, but it's easier to locate a small number of large objects in utility rooms that 800 roughly 8" to 10" cube transformers, one near each outlet!

[You cannot use resistors or any other kind of "dropper" box, as the voltage drop across such things is proportional to the load. If it drops 37V with a 3KW load, it would drop 0,37V with a 30W load. Plus wasting massive amounts of energy].

 

[Tony Stewart]

You may be increasing VAR consumption 10% just from excitation current, in case you pay for VARs. Then you would need a VAR compensation Cap to improve p.f.

Must be EV charge ports?
I agree on the central auto-transformer approach. That's going to be one noisy parking lot! I'd also be concerned about EMI noise suppression.

Where did you find a 200kW converter for $69 alibaba ?

In Winnipeg we had power outlets for engine heaters and load switching for every row on an hourly basis for about 500 stalls. In the winter we never had a heating system even at -40'C because the Burroughs peripheral factory had so many large computers, and disk drives heating the building in the factory. I think we were the power company's best customer. But even some old cars would have lousy batteries and fail below -30'C so we had a transformer on a dolly that could start a car with over 500A @ 12Vdc

 

[Tony Stewart]

I understand 120/208/240 and 270/400 V lines cannot share conduit.
The American EV market screwed up without considering commercial power availability yet Tesla figured it out. EU seems to have been wiser.

At some point soon both SAE and EV mfrs will figure this out, and it must be an option. New parking lots with streetlamps will need some planning for ease of future distribution so that re-trenching and wiring everything is not a waste.

A 200+ kVA transformer might supply 6 to 10W/$ but then there are all the distribution wiring , trenching & charge port costs.

 

[Diver300]

Whether an EV in America is using the type 1 socket or the NACS (Tesla) socket, charging on AC can get to 19.2 kW (80 A on 240 V split-phase, and as I understand it, most houses in America have electrical connections that can supply that,

In mainland Europe, 3-phase 230 V supplies are common, giving between 11 kW (16 A) and 22 kW (32 A). In the UK, single phase is the norm (although 3-phase is being fitted on new houses) and 7 kW (32 A) charging is usually possible, which is plenty for overnight charging.

Anyhow, as far as AC charging goes, the American system is only slightly less powerful that the largest European chargers.

For rapid DC chargers, which can be anything from 50 kW to 350 kW, they need dedicated feeds, and can't be just wired into domestic supplies like the AC chargers. It doesn't much matter what voltage the DC chargers run off, as dedicated supplies will have to be installed along with the chargers.