Toyota AC Outlet Supply Accessory (Not charging cable)

if they actually make it for n/a, they'll probably do it right

 

The inverter circuit being shown in that post is a single-phase one, producing 240 Vrms.

It is packaged as a unit with 120 Vrms split-phase output, but that's entirely accomplished by feeding the circuit's single-phase output into a center-tapped step-down transformer. The circuit synthesizing its waveform doesn't know or care about that.

If you have a design that is going straight + to − by flopping both sides of the H-bridge on every single transition, you can use the switches more efficiently just by changing your algorithm to switch them differently. If it doesn't add to manufacturing cost, I don't see much reason not to do so.

That would be lovely, but then, what did the non-n/a markets do to deserve getting it done wrong?

 

It doesn't form a neutral?

Most of what I work on is either 3-phase or single-phase split but my understanding is that these tiny single-phase devices have a single leg - no H bridge. You either close to the top or to the bottom.

Better devices have two legs, and form a neutral. I'm working with a 25kW one right now. But these $50-$100 devices sold at Harbor Freight and Amazon aren't like that. But they work for having a single hot.

 

Not the waveform-synthesizing part of the circuit, no. The final output of the whole unit has a neutral, but that's just the center tap of the output transformer. (More recent offerings from PlugOut Power have even been two separate boxes, a single-phase 240 Vrms inverter and the center-tapped transformer in a separate box.)

Maybe if you had a bit of schematic to post that would be easier to picture.

Of course in a single-phase system, there's nothing obvious to tell you which conductor is "neutral". In a grounded wiring system, it's just the one that you happened to bond to the ground. The NEC doesn't even really say "neutral" and "hot": it says "grounded circuit conductor" and "ungrounded circuit conductor". The difference is pretty invisible electrically unless there's a ground fault (or you're deliberately using a tester to see which one has continuity to ground). Other than that, they're both just circuit conductors, and they both need to conduct both ways depending on which half of the cycle you're in.

I think I'm still picturing a minimum of two switches. And at the very least some brief spells of zero, because whenever switching from one to the other, you want to safely avoid overlapping them, so the magic smoke stays in.