Question: US 220 vs Aussie 220

This is probably just a matter for careful selection of a circuit breaker. Transformers have a volt-second limit (and that means 50 Hz at rated voltage is more likely to saturate the core than 60 Hz at rated voltage). The volt-second limit applies to the UNLOADED transformer, though, so a blade-welding cycle (with a nice big load on the secondary while current is flowing in the work) is likely to be trouble-free. If the transformer is switched on before the blade parts are butted, it could saturate and blow the main breaker (so putting a 20A breaker local to the unit would be more convenient if it needs resetting).

Another saturation protection would be a good fast-blow fuse (because if it isn't the breaker or fuse that blows, it's the copper in the transformer).

Isolation is expensive and unnecessary. You can use a simple bucking transformer (the 240V 60 Hz rating of a US transformer for saturation of the core corresponds to 200V 50 Hz rating) that lowers 220V to 200V.

Of course, 'toroidal' refers to the shape, it still has an iron core.

Most modern computer supplies either have a switch, or autoswitch. I haven't seen a '110 PS' in decades. Some, which use a manual switch, have a hard-to-get-to fuse. The fuse can pop, loud.

Were those 60 or 50 Hz ones? I think he'll have a hard time getting a 50Hz transformer there of sufficent size.

Actually, I did state that I forgot to switch this one. It was a

110/220, and I just plain got distracted and forgot to move the slider. Won't make that mistake again... And it wasn't a fuse that went, I opened it up hoping to find a fuse. Think it was a cap that blew. The noise was close to a firecracker. I've never heard a fuse do that, which is not to say they can't.

Jon

I can't find the post describing it, but if this oven is just resistive, frequency does not matter, period.

And it may be possible to get 240V heaters for it to replace the 120V. There may some other ugly hack possible; put a another resistive heater of the same load in series, etc.

Copper takes 100% overload for a long time. In power distribution systems hours..it can glow read hot and still survive just fine.

Aluminum is a different beast.

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Another saturation protection would be a good fast-blow fuse (because if it isn't the breaker or fuse that blows, it's the copper in the transformer).

Dad's still alive. Almost lost him this spring, but doing reasonably well right now. He's 82. I'm just shy of 60. No Roth blood, but know a lot of Roths, and lived between Pool and Milverton for a while as a kid. Whitney Farms ring a bell?? Or H&S Electic? Or AB Snyder Electric (Dad's older brother), Quality Lighting, Gemor Electric, Aden Fry? Ron Hoy Electric, Gosen Electric?

Virtually every power supply I have around here is either "universal" or 115/230. Never seen a 120/240 one, and the universals are generally good from 100 to 240 - with the odd one being 90 to 250.

Ferrite's no good for 60hz and any kind of power.

And the ferrite iron is for high frequencies -- perhaps a DC-DC switching mode converter, not for low frequencies like 60 Hz or 50 Hz. Not even for aircraft 400 Hz.

Enjoy, DoN.

And although the copper may survive, the insulation very well may not.

Did not mean to imply it was; just pointing out that toroids use magnetics just as old fashioned transformers do....they ain't magic.

The usual distribution system in Australia is 3 phase 415 volt, 50 Hertz to the street, but each customer gets a phase to neutral to their house. Phase to neutral is in fact not 220 volts but is more like 230 or 240 volts. The number of customers on each phase is managed to maintain a reasonably even load on each phase. Until recently it was difficult to get 3 phase 415 volt power to a private dwelling, but the increase in large air conditioning split systems has made it relatively easy to get 3 phase.

Yes this is very true. I guess bare overhead lines are a little different

2------------------------- >Copper takes 100% overload for a long time. In power distribution systems

239.6 volts in conjunction with the N.American world standard of 240v

Most of those are familiar. Snyder, Gosen, Gemor, Ron Hoy. I was in Kit.

Snyder joined up with Tschirhardt? now T&S Electric?. I hung out with Cronin at work.

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Dad's still alive. Almost lost him this spring, but doing reasonably well right now. He's 82. I'm just shy of 60. No Roth blood, but know a lot of Roths, and lived between Pool and Milverton for a while as a kid. Whitney Farms ring a bell?? Or H&S Electic? Or AB Snyder Electric (Dad's older brother), Quality Lighting, Gemor Electric, Aden Fry? Ron Hoy Electric, Gosen Electric?

I always just assumed it was too expensive but was much better (less losses). Any reasons for that known?

The maximum working flux density of ferrite is only about 1/3 of that for silicon iron. A ferrite 50/60Hz power transformer would be more than 3 times bigger than the silicon iron equivalent

However the high frequency losses are much lower and at frequencies higher than a few thousand Hz ferrite design are smaller and more efficient.

High power designs are common in the frequency range a few hundred KHz to a few MHz

Jim