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The real reason why North America uses 120v instead of 240v.
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tooki:
For what it’s worth, I think the Swiss receptacle system (SN 441011) is extremely elegant: it consists of four receptacle types: 10A and 16A, in single-phase and three-phase. 10A plugs fit into 16A sockets (not so special), but the thing that is unique (as far as I’m aware) is that single-phase plugs fit into three-phase sockets.

This is extremely practical, for example in laundry rooms, which often have three-phase sockets for the washer and dryer, but which then accept a modern single-phase heat pump dryer without any adapters.

Standard 2-pin Europlugs (CEE-7/16, 2.5A) fit into them, too (the standard requires sockets to accommodate them) but not standard European grounded CEE 7/7 (Schuko/F) or the 16A 2-pin (CEE-7/17) European plug.

Old versions of the standard had some exposed-metal hazards, but sleeved pins have been required for years, and recessed sockets are now required for all new installations. (In the past they were required only in wet spaces.)

It’s curious that all of the newest outlet standards (like the new ones in Brazil and South Africa) are based on the IEC 60906-1 socket, which itself is a tweaked version of the Swiss socket. (All mutually incompatible, of course…)
Zero999:

--- Quote from: tom66 on November 27, 2022, 10:28:57 am ---
--- Quote from: JPortici on November 25, 2022, 09:17:29 pm ---In italy there should still be some areas in Turin and Rome with three phase 230V, no neutral (residential utilities are connected between two phases)
however the last i heard of it is that they started converting to the current 400V 3phase + neutral

--- End quote ---

I know Belgium is similar, in rural areas.
Apparently some electric vehicles cannot charge off such 230V 3ph, they require a neutral (they will charge on the slow charger, but not on a wall box.)

--- End quote ---
That sounds like bad design to me.

If it was designed properly, it would simply rectify the mains to DC, then power everything from that. It shouldn't be difficult to make a charger which would work from 210VAC to 270VAC single phase, or 210V to 440VAC three phase.
james_s:
The main advantage I see of 120V is that lower voltage incandescent lamps are substantially more efficient. That is pretty much moot now but for most of the first century of electrification lighting which was primarily incandescent was the largest consumer of electricity. It may be arguably safer, but even 120V can and does kill people. Safety focus should be on preventing shocks more so than surviving them.
IanB:

--- Quote from: Zero999 on November 30, 2022, 05:14:16 pm ---That sounds like bad design to me.

If it was designed properly, it would simply rectify the mains to DC, then power everything from that. It shouldn't be difficult to make a charger which would work from 210VAC to 270VAC single phase, or 210V to 440VAC three phase.

--- End quote ---

There are some special design considerations relating to car chargers concerning the neutral and grounding arrangements, which may be why this limitation exists. I know the neutral is not earth/ground, but I suspect the problem is regulatory rather than technical.
Siwastaja:

--- Quote from: NiHaoMike on November 25, 2022, 01:25:18 pm ---Why not have 120V be 2x 60V to ground? Wouldn't that be the safest way to have 120V?

--- End quote ---

I found out by coincidence that there is a specific market for construction site power tools, in UK, where it is arranged exactly like this. The argument for it is safety, indeed: they install a step-down transformer to go from 240V to 120V, with a center tap on the output, which is then earthed. Someone who gets shocked between L & earth or N & earth only sees 60VAC, which, while slightly over modern safety limits, is not that dangerous.

I found it out in a project where we wanted to equip a robot supplied by 6s li-ion pack with a powerful construction site vacuum cleaner. So I designed a 22V to 74V (barely below the LVD safety limit for DC) 4-phase 750W boost converter. What next - find a 120V construction vacuum. Not going to order from the USA or Japan due to tight schedule - but quick Googling revealed there exists a complete market for 120V vacuum cleaners and power tools in the UK, so got one from there. And of course, brushed motor vacuum cleaners run from DC just fine, even better than from the AC supply. It was a truly capable solution, with 50cm wide nozzle it picked up quite heavy dirt, gravel etc.
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