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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
I have seen some person make a big hv transformer called "porkchop". Well i now have a laminated iron core that uses e sections and i sections. the E section is about 3 and 1/8th inch wide and 4 5/8 inch tall. The i section is 3/4 inch wide and 4 5/8 inch tall. The core came from a vacuum tube power television. How many primary and secondary turns should i use for a 6000 volt transformer that is good for at least 100ma. Oh and i forgot the upper part of the E section is 3/4 inch tall, as well as the bottom, and the middle part of the E section is 1 5/8 inch tall. I have already removed the sections so all i have to do is take the bobbin apart and wind all of the windings.
UPDATE: which windings would go on the bobbin first, the primary or secondary windings?
Registered Member #1450
Joined: Sun Apr 20 2008, 09:59PM
Location:
Posts: 10
Hmmm
The cross-sectional area of the steel core will determine your maximum power output - there's sure to be a formula for this - but 600 VA seems a bit optimistic for a core this size based purely on the size of other transformers with a similar power rating. What total thickness of laminations do you have?
Do you need a whole 100 mA or can you put up with lower voltage?
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
If you have decided you must have an output of 6kV/100mA @ 60Hz, then all the rest of the design equations will flow from that, including the minimum size of the core. Without calculating anything at all, I can assure you that such a transformer will be large, heavy, use a great deal of copper wire and other materials, and be an expensive undertaking to build. It would almost certainly be cheaper to buy a second-hand valve-era transformer, such as 3kV-0-3kV @ 250mA on ebay, for which I would expect to pay upwards of £80 - say $160 and possibly quite a bit more if other bidders are interested - certainly much cheaper than trying to build a comparable one yourself.
But if you still want to go ahead winding your own, there is a certain amount of transformer design freeware around on the web.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Shoot. I can put up with 50 ma or even less... Just something i would like to try. Well right now i just want to know how few primary windings can i have? I would like to have about 1 volt per turn or even more if at all possible. I only have like 300 feet of wire so i will just go for a 1000 volt transformer at first. That will be good enough for the vttc circuit i made up. I figure i will need about 6 inches per winding so 600 volts is a more realistic goal. Sure it is 10 times less than what i would like but it will at least be able to power my little vttc and be exactly withing my tubes specs. The thickness of the core when it is put together is around 1 1/2 inches.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
I'd wind 10 turns on the core, then get a mains transformer with >12VAC output, then connect your mains transformer to your 10 turns via a 100-200ohm >2W resistor. Turn the thing on, measure the voltage on your 10 turns, divide by 10 and you have the approximate volts per turn you can expect. I really doubt it will be more than 1V per turn, most probably under 0.5V.
Registered Member #187
Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140
Non-inverter type microwave oven transformers are fairly easy to re-engineer. The important thing to remember is that the primay impedence has been designed to work with 120VAC (and lower, if you use a variac). As long as you leave the primary intact you can do anything you want with secondary side.
When I built my 2x811a VTTC, I heated the transformer up on a hot plate just enough to soften the lacquer or varnish, and then I just counted layers and peeled them off. If you prefer you can always remove all the sec windings and make your own.
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