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Registered Member #242
Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210
I've started work on my winding jig. I'll try to have some pics up later tonight. I've got a few questions, first off, how much polyurethane did you guys use? I'd prefer to not buy the 1 gallon can if I dont have to. I also ordered parts to build a gate drive similar to Steve Conner's. How is the Rogowski coil implemented? I'm mostly looking for the position with respect to the primary, and I assume I'll need to use shielded cable?
Well thats all for now, hopefully I'll be able to get some work done tonight
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Hi jrz
The Rogowski coil is a toroidal air cored current transformer. I made mine by wrapping some left-over secondary wire round a 6" length of plastic hose (about 3/8" diameter) and then bending the hose round into a donut shape and joining the ends with tape.
I put it round a conductor of the primary circuit so that the full primary current flows through the middle of it. The whole point of the Rogowski coil is that it only detects currents that pass through the donut hole. To avoid the single turn effect and help improve the cancellation, I passed the wire from the far end back down the middle of the hose.
Registered Member #242
Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210
I've got my winding jig ready to go and I put 4 coats of poly. on the bare form. I'm just about ready to start winding it. It was suggested previously in this thread to use about 2000 turns and a 2:1 ratio. Now do I want to stick to the 2:1 ratio or 2000 turns? If I stick with the 2000 turns, I'll end up with a 2.7:1 ratio. and if I stick to the 2:1 ratio, I'll end up with 1400 turns.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
I see no reason at all for a 2:1 ratio. By all means, use a longer winding and get the lowest operating frequency you can. Even a 3:1 ratio is a little "fat" in my experience. I typically go with 4:1. But really, winding ratio isnt as crucial as some might say it is. Getting a lower Fr so you can use more bang energy *is* crucial.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I'd go with the 2.7:1 and 2000 turns. The reason for a "Stubby" secondary is that it allows higher coupling, but the OLTC isn't so demanding of coupling as the DRSSTC. I got plenty coupling on the OLTC 2 with its 3:1 (30" x 10") secondary.
Registered Member #242
Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210
There is a seam in the cardboard that is exposed now from when I removed the yellow paper. How should I fill it in? I put a piece of masking tape over it, but its still alittle flimsy. Should I put some Poly. over the masking tape?
So should I put more than 2000 turns on it? Is it possible to have a resonant frequency that is too low?
I ordered a bunch of parts last wednesday, hopefully they will be here shortly.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
There is a seam in the cardboard that is exposed now from when I removed the yellow paper. How should I fill it in? I put a piece of masking tape over it, but its still alittle flimsy. Should I put some Poly. over the masking tape?
Is there a deep grove left? The seam in my tube just left a bit if a bump, so i just wound over it.
So should I put more than 2000 turns on it? Is it possible to have a resonant frequency that is too low?
Well, its only too low if you cant tune your primary low enough to match, so keep in mind how many caps you will have, and what your primary coil will be. There probably isnt much to be gained from more than 2000 turns. Be sure to top it off with a good sized toroid, generally the outer diameter of the toroid should be equal to the length of the coil (thats my general rule anyway).
Registered Member #242
Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210
the groove is pretty big, I'd say about 1/16th wide and 1/16th deep. the masking tape covers it, but its pretty flimsy. I had about 10-15 turns on it and I noticed it was mis-shaped there. I'll try putting some poly over a small section and see how that does.
I've got 24 0.56 caps to use, so I'll be able to have 13.44uf at 1000V or 6.72 uf at 2000v. Which brings up another question...Would I be able to use a double-sided PCB for a bus bar to mount these caps? I have some 1-oz double-sided boards lying around. The 1-oz is pretty thin, but I might be able to beef it up with some addiional wire.
Do I need to have the large topload on there all the time? or is it for when I start getting into higher powerlevels? I have 4" dryer duct toroid already made up (15" overall), that I'd like to use for testing at lower powerlevels.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Yep, you need huge topload and secondary.
I hope i'm 'breaking no rules' with this, pic, , but just to get the image of size of toroid and secondary Steve used. 10x30inch is pretty big. Maybe you could get away from this by using thinnger wire, but you should anyway keep frequency very low, 50-60kHz in overall.
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OLTC project
, but just to get the image of size of toroid and secondary Steve used. 10x30inch is pretty big. Maybe you could get away from this by using thinnger wire, but you should anyway keep frequency very low, 50-60kHz in overall.