Transformer theory

[paggerman]

Ina previous post I have mentioned the great expense of 'proper' transformers in Australia. I'm sure it's even worserer for Tubeswell in NZ. I just wanted some thoughts on perhaps hacking a solution. Here in Australia we have 240VAC mains (most of the time). If I wanted to get an unrectified power supply of of 400VAC could I use a step down tranny of 240VAC-50VAC and then back to back it with a 240VAC-30VAC step down tranny? And if I wanted 300VAC I could use the same 240-50 and then up it with 240VAC-40VAC transformer? And for 360VAC I could use 240-18 and 12-240? If both have the same VA rating, is there anything else I should know apart from the things that go zap?

[Wilder Amplification]

Ina previous post I have mentioned the great expense of 'proper' transformers in Australia. I'm sure it's even worserer for Tubeswell in NZ. I just wanted some thoughts on perhaps hacking a solution. Here in Australia we have 240VAC mains (most of the time). If I wanted to get an unrectified power supply of of 400VAC could I use a step down tranny of 240VAC-50VAC and then back to back it with a 240VAC-30VAC step down tranny? And if I wanted 300VAC I could use the same 240-50 and then up it with 240VAC-40VAC transformer? And for 360VAC I could use 240-18 and 12-240? If both have the same VA rating, is there anything else I should know apart from the things that go zap?

So you're talking hitting the primary of the first tranny with 240 to step it down at the secondary, then hit the secondary of the 2nd transformer with the stepped down voltage to kick it up to 400VAC at the primary? Why not just get a 240VAC - 400VAC step up tranny?

[black_labb]

So you're talking hitting the primary of the first tranny with 240 to step it down at the secondary, then hit the secondary of the 2nd transformer with the stepped down voltage to kick it up to 400VAC at the primary? Why not just get a 240VAC - 400VAC step up tranny?

the issue is availability. its hard to find them in australia and NZ.


i've been using transformers from Antek - Your reliable source of transformers, power supplies, and more. you have to ship them from america (which isnt cheap) but the price is great and you pay flat shipping up to 20lbs, so you can benefit from getting 2-4 depending on the size.

back to back transformers will work, but you will be using double the iron/weight and double the losses from transformer inefficiencies.

what kind of amp size wise are you planning?

[Bruce / Mission Amps]

Ina previous post I have mentioned the great expense of 'proper' transformers in Australia. I'm sure it's even worserer for Tubeswell in NZ. I just wanted some thoughts on perhaps hacking a solution. Here in Australia we have 240VAC mains (most of the time). If I wanted to get an unrectified power supply of of 400VAC could I use a step down tranny of 240VAC-50VAC and then back to back it with a 240VAC-30VAC step down tranny? And if I wanted 300VAC I could use the same 240-50 and then up it with 240VAC-40VAC transformer? And for 360VAC I could use 240-18 and 12-240? If both have the same VA rating, is there anything else I should know apart from the things that go zap?

What the heck are you trying to do?
That's a real Rube Goldberg thing....

Rube Goldberg

If you want 400vac whats wrong with a PT that just does that?
We have lots of trannys here that take 120vac to 400vac.
Maybe there is one that has a split primary 120v-240v to 400vac.

[Wilder Amplification]

What the heck are you trying to do?
That's a real Rube Goldberg thing....

Rube Goldberg

If you want 400vac whats wrong with a PT that just does that?
We have lots of trannys here that take 120vac to 400vac.
Maybe there is one that has a split primary 120v-240v to 400vac.

According to the post above, they're hard to find in Australia/NZ and the shipping isn't cheap to ship them from the US.

[Albert Kreuzer]

If you want to get 400V from a tranny designed for 240, it will most likely get into saturation and act like a short circuit.

Don't ask how I know...

[Steve Conner]

Come on guys, Australia and New Zealand aren't some kind of third world countries.

And if they were, you could do this: AfriGadget Blog Archive Home Made Welding Machine

Hint: See if you can get an industrial control panel transformer. I've seen ones intended for stepping 415V down to 240, and you can run them backwards.

[dai h.]

yeah that doesn't make any sense (and even in third world countries, I do think there are power transformers avail.). 5 seconds with google turns up one in Oz:

Transformers - Hammond & generic

In NZ Simcha Delft makes OTs that have a good reputation (as another example). The Radiotron book--wasn't that published in Australia? AUS/NZ is not exactly a technological backwoods. Finding ham radio people and asking them for part sources might help as well.

[tubeswell]

Well I have several sources for NZ made transformers - but they are custom made and would be expensive to ship to Oz because they weigh 1/2 a ton each.

@ paggerman FWIW Evatco in Queensland supplies tube amp stuff (including transformers)

Transformers - Hammond & generic