US 220V 20A TO CHINA 220V 10A MAHJONG MACHINE

[James Wilkinson Sword]

My supply is 246 to 256 volts. It should be 230. They claim it's within spec....

Digital meters are all pretty accurate, at least mine are (expensive and cheap ones). They all agree with each other and the electrician's calibrated one he brought with him.

The voltage used to stay exactly 241, but they changed the substation across the road (like your pole transformers, but this serves 50 houses) - some kind of upgrade for more housing, solar panels, or just routine replacement, I don't know. Anyway, it was never set right, because they guy that sets them up around here doesn't care and just makes them somewhere within spec. The last guy made it as precise as possible.

I've seen fine (5 volt) adjustments on the back of stereos etc post-valve technology.

[James Wilkinson Sword]

Yes, but they were happy to take 220 to 250v.

Desktop supplies are switching aswell and usually don't have the selector anymore. Although I've seen some (cheaper?) switching supplies which won't take a wide enough band of voltages to go from 110 to 250.

[James Wilkinson Sword]

Too little voltage, too much current, too much heat or too much wire.

Too much voltage, too much arcing, bigger stronger switches required, heftier insulation.

Look up the safety regs list for getting electrical equipment to pass the tests. For American stuff, it's all to do with current overloads and fires. For the UK it's all to do with arcs to the frame and fingers touching live parts.

[James Wilkinson Sword]

I've never really thought about it, but without some complicated electronics in there, how can it sum three things?

[James Wilkinson Sword]

It would have been quieter. And we wouldn't have had to shield all the stereo and TV circuitry.

[James Wilkinson Sword]

I just told you, I don't have circuit breakers. There is no RCD.

[James Wilkinson Sword]

I doubt it, my degree involves Maths.

[James Wilkinson Sword]

Is that supposed to make it sound less?

[James Wilkinson Sword]

Electronically, no. But using simple coils and magnets which the originals did, subtracting x from y is simple, but when there's 3, how the f*ck do you do that? Especially as you have one hot leg at opposite phase to the other.

[James Wilkinson Sword]

they are now.

[James Wilkinson Sword]

I wasn't aware quite how third world the USA was.

[Dev Null]

It's single phase.

[James Wilkinson Sword]

Diesel is a criminal hacker, he doesn't have a brain, don't bother reasoning with him.

[trader_4]

Just stop already, you're in way over your head.

[gfretwell]

It is all done by how they wind a small toroid transformer. The currents null each other out unless some is going somewhere other than through that transformer. Then an OP amp samples that current and fires a solenoid that trips the breaker. This is a GFCI breaker.

On a 120/240 there will just be two stacked with an extra winding in the transformer for the neutral.

[gfretwell]

Not particularly. The line to line will get measured just like any other single phase and the neutral current will get subtracted from any imbalance.

[Davej]

The typical home only needs 240V for a few high-power items, so why wire the whole house for an unnecessary voltage? Adding a center-tap to a transformer is cheap. Rare to need portable 240V items where GFCI would be important.

[Davej]

No. Have an electrician run a new 240VAC line from your circuit breaker box to an appropriate outlet. Of course USA power is 240V

60Hz rather than Chinese 220V 50Hz so you will need to check the power specifications on your machine. An auto-transformer could be used to reduce the voltage. You cannot safely connect out-of-phase outlet circuits to be used together as you propose because of the resulting short-circuit behavior.

[trader_4]

Which is ridiculous because there is no short circuiting behavior. The op could do what they proposed and get 240v from two circuits on different legs. It would work, but I don't see a code compliant way.

[Davej]

You want a single wire bundle to come from the breaker box to the

240V outlet. You do not want to create some absurd inductive loop by connecting two phases routed from different wired circuits. Added inductance can reduce the reliability of short-circuit breaker action. Also you want to use a 2-pole 240V breaker that will trip both legs.