I cannot imagine why you still get transformers with one secondary wound over another. It is wasting money. you normally wind two secondaries together so that the resistance is the same and secondary voltage is the same. Sorry if I comment so late in the thread.
Good for you. Most others prefer to simply buy a PT that fits the project & then move ahead.👍
If you like to sit by your winding machine, that is your preference. Have a beer or two as you progress. 😀
bifilar wound secondaries..., I do that on my solid state ptx builds...
i agree, the benefits are to good to ignore...
...but are hard to find, especially in tube equipment power transformers. The voltage between two adjacent turns always is half the total voltage, which may stress the wire insulation.
Best regards!
Best regards!
That’s why the heavy build stuff is always used in toroids - the really thick polyurethane. And why there seems to be an upper limit on how much voltage there is in a single bifilar winding. They don’t run them into the kV. Even the Big Antek is wound as 4x475V (2X 950CT). Insulation just won’t support 1900V, bifilar.
I own one of the oldest transformer companies in South Africa started in 1961. I have people employed to watch the 60 winders of different sizes. For me I can design and manufacture any transformer I like.
In that case you can use a split bobbin. Wire gage for tube output transformers are small.
Our problem is exporting small numbers of transformers, the shipping cost exceeds the product cost with orders of magnitude due to their weight. If it cannot fill a palette it is commercially not feasible. I have sent a few guys here quotes for transformers made to their specifications but they declined as soon as they se the shipping costs. My quotes are usually F.O.B. but is scary since we are about 6000 km from everybody, same as the Ausies and Kiwis.
i built an isolation transformer using the bifillar windings for both primary and secondary...
230:230 vac, on a bobbin, the traffo still in service after 20 years and counting..
for tube amps, using the full wave doubler, there is no need to wind bifillar...
i have nylon bobbins for this, Antique Sound Labs used split bobbins for their OPT's, single ended and push pull, as per Norman Crowhurst, vertical sectioning cuts shunt capacitance in half...
Good to know. But this thread is for vacuum tube amps.
Show us something of that kind you have personally built. And how you got there.
Few people need or want a building powered by 30 winders. 👎
Early in my journey to engineering I did work for Ferranti, a well known transformer company of the past.
Mostly 3-phase, the kind that is shipped out the door on a railway flat car.
I worked in the test lab. But did spend time in the steel yard helping move transformer iron.
A very different environment.😀
Well, this would be illegal in my country. Isolation transformers are wound on split bobbins to fulfill the >4 kV isolation requirement according to DIN EN 61558-1 et al.
Best regards!
i only did it once and only because i wanted to know that it works, it did okay, this is something i am not proud of and will never tell another to do..
i have split bobbins to use in case i want to do another isolation transformer..
Yes, but aren't we talking about mains/power transformers? Anyway, to wind a PP OT's primary bifilarly also isn't a good idea - unless you're about to construct a Unity Coupling OT a la G. Gow/F. McIntosh.
Best regards!
This originally started as a mains transformer discussion. But some of us do use bifilar wound power toroids as tube OPTs. Typically with somewhere around normal operating voltages on them. They can be run a bit over, if you’re willing to live with reduced bass response. But for full response to 50 Hz, gotta keep it a 340V p-p, which is no worse than strapping the primary for 240.
I’ve also relied on audio coupling transformers to isolate the sound system from the disco light show that ran “hot”, even though the trafo wasnt exactly rated for that duty. The modern version STILL uses the trafo, even though all the triacs are driven by 8kV rated optoisolators. Without it there’s an awful ground loop hum so the trafo stayed.