Forums

Trying to Get Less Leakage and Picture Link of Transformer

Started by D from BC October 5, 2011
Here's a 1:1 transformer I made.
http://www.members.shaw.ca/chainsaw/SED/xformer2.JPG	
1.4MB

Materials
EFD cores
Coax cable
Ignore the purple wire.

Primary inductance: 200uH@700khz
Leakage inductance: 220nH@1Mhz

I want less leakage. 22nH or less leakage would be nice.

I figure in order to reduce the leakage I need to get my secondary and 
primary closer together. iows I need coax with less inner insulator or 
perhaps switch to parallel bonded magnet wire or go twisted pair.
True?
Or maybe I'm overlooking something.

D from BC <myrealaddress@comic.com> wrote in news:fGQiq.560399$JZ5.526086
@unlimited.newshosting.com:

> Here's a 1:1 transformer I made. > http://www.members.shaw.ca/chainsaw/SED/xformer2.JPG > 1.4MB > > Materials > EFD cores > Coax cable > Ignore the purple wire. > > Primary inductance: 200uH@700khz > Leakage inductance: 220nH@1Mhz > > I want less leakage. 22nH or less leakage would be nice. > > I figure in order to reduce the leakage I need to get my secondary and > primary closer together. iows I need coax with less inner insulator or > perhaps switch to parallel bonded magnet wire or go twisted pair. > True? > Or maybe I'm overlooking something. > >
A 1 in 1000 ratio looks pretty nice to me.......
On Oct 5, 6:03=A0am, D from BC <myrealaddr...@comic.com> wrote:
> Here's a 1:1 transformer I made.http://www.members.shaw.ca/chainsaw/SED/x=
former2.JPG=A0 =A0
> 1.4MB > > Materials > EFD cores > Coax cable > Ignore the purple wire. > > Primary inductance: 200uH@700khz > Leakage inductance: 220nH@1Mhz > > I want less leakage. 22nH or less leakage would be nice. > > I figure in order to reduce the leakage I need to get my secondary and > primary closer together. iows I need coax with less inner insulator or > perhaps switch to parallel bonded magnet wire or go twisted pair. > True? > Or maybe I'm overlooking something.
Actually, you probably are. Try a non-progressive winding - count the number of turns, then go through the four cores putting on half that number of turns before coming back through the four cores putting on the rest of the turns in the same sense, so that the end of the coaxial cable emerges from same point as where the widing started. At the moment you have a - very weak - external field produced by the imperfectly coaxial nature of your coaxial cable as it makes its way around the loop in the plane defined by the fours cores; with the non- progressive winding this loop is much reduced. The "imperfection" does seem to be about 0.1% - a non-progressive winding might well give you your next factor of ten reduction. Progressive versus non-progressive windings are discussed in Rayner and Kibble's "Coaxial AC Bridges" a.k.a."Tricks from the National Standards Labs". http://www.amazon.com/Coaxial-AC-Bridges-B-Kibble/dp/0852743890 They get mentioned here from time to time. -- Bill Sloman, Nijmegen
Thanks
I'm inexperienced in how great the ratio can be.
I'm studying the leakage inductance formula on
http://www.vias.org/eltransformers/lee_electronic_transformers_04_08.html
to get an idea of ways to reduce the leakage further.

On 10/4/2011 9:36 PM, Sjouke Burry wrote:
> D from BC<myrealaddress@comic.com> wrote in news:fGQiq.560399$JZ5.526086 > @unlimited.newshosting.com: > >> Here's a 1:1 transformer I made. >> http://www.members.shaw.ca/chainsaw/SED/xformer2.JPG >> 1.4MB >> >> Materials >> EFD cores >> Coax cable >> Ignore the purple wire. >> >> Primary inductance: 200uH@700khz >> Leakage inductance: 220nH@1Mhz >> >> I want less leakage. 22nH or less leakage would be nice. >> >> I figure in order to reduce the leakage I need to get my secondary and >> primary closer together. iows I need coax with less inner insulator or >> perhaps switch to parallel bonded magnet wire or go twisted pair. >> True? >> Or maybe I'm overlooking something. >> >> > A 1 in 1000 ratio looks pretty nice to me.......

"D from BC" <myrealaddress@comic.com> wrote in message 
news:fGQiq.560399$JZ5.526086@unlimited.newshosting.com...
> Here's a 1:1 transformer I made. > http://www.members.shaw.ca/chainsaw/SED/xformer2.JPG 1.4MB > > Materials > EFD cores > Coax cable > Ignore the purple wire. > > Primary inductance: 200uH@700khz > Leakage inductance: 220nH@1Mhz > > I want less leakage. 22nH or less leakage would be nice. >
A single secondary foil turn over each coil? Is that 3 or 4 turns on the sec? Cheers
On 10/5/2011 8:27 AM, Martin Riddle wrote:
> "D from BC"<myrealaddress@comic.com> wrote in message > news:fGQiq.560399$JZ5.526086@unlimited.newshosting.com... >> Here's a 1:1 transformer I made. >> http://www.members.shaw.ca/chainsaw/SED/xformer2.JPG 1.4MB >> >> Materials >> EFD cores >> Coax cable >> Ignore the purple wire. >> >> Primary inductance: 200uH@700khz >> Leakage inductance: 220nH@1Mhz >> >> I want less leakage. 22nH or less leakage would be nice. >> > A single secondary foil turn over each coil? Is that 3 or 4 turns on the > sec? > > Cheers > >
The 3 or 4 turns of the purple wire is not part of the transmission line transformer. It's just something left over from other tests. Foil over each coil? Nah... I don't get that. I don't think wrapping the coax with foil will increase the magnetic linkage between shield and core wire.
On 10/5/2011 12:41 AM, Bill Sloman wrote:
> On Oct 5, 6:03 am, D from BC<myrealaddr...@comic.com> wrote: >> Here's a 1:1 transformer I made.http://www.members.shaw.ca/chainsaw/SED/xformer2.JPG >> 1.4MB >> >> Materials >> EFD cores >> Coax cable >> Ignore the purple wire. >> >> Primary inductance: 200uH@700khz >> Leakage inductance: 220nH@1Mhz >> >> I want less leakage. 22nH or less leakage would be nice. >> >> I figure in order to reduce the leakage I need to get my secondary and >> primary closer together. iows I need coax with less inner insulator or >> perhaps switch to parallel bonded magnet wire or go twisted pair. >> True? >> Or maybe I'm overlooking something. > > Actually, you probably are. Try a non-progressive winding - count the > number of turns, then go through the four cores putting on half that > number of turns before coming back through the four cores putting on > the rest of the turns in the same sense, so that the end of the > coaxial cable emerges from same point as where the widing started. > > At the moment you have a - very weak - external field produced by the > imperfectly coaxial nature of your coaxial cable as it makes its way > around the loop in the plane defined by the fours cores; with the non- > progressive winding this loop is much reduced. > > The "imperfection" does seem to be about 0.1% - a non-progressive > winding might well give you your next factor of ten reduction. > > Progressive versus non-progressive windings are discussed in Rayner > and Kibble's "Coaxial AC Bridges" a.k.a."Tricks from the National > Standards Labs". > > http://www.amazon.com/Coaxial-AC-Bridges-B-Kibble/dp/0852743890 > > They get mentioned here from time to time. > > -- > Bill Sloman, Nijmegen
I'll rewind it and test again. Will post test results. Thanks..
On Oct 5, 6:07=A0pm, D from BC <myrealaddr...@comic.com> wrote:
> On 10/5/2011 12:41 AM,BillSlomanwrote: > > > > > > > > > > > On Oct 5, 6:03 am, D from BC<myrealaddr...@comic.com> =A0wrote: > >> Here's a 1:1 transformer I made.http://www.members.shaw.ca/chainsaw/SE=
D/xformer2.JPG
> >> 1.4MB > > >> Materials > >> EFD cores > >> Coax cable > >> Ignore the purple wire. > > >> Primary inductance: 200uH@700khz > >> Leakage inductance: 220nH@1Mhz > > >> I want less leakage. 22nH or less leakage would be nice. > > >> I figure in order to reduce the leakage I need to get my secondary and > >> primary closer together. iows I need coax with less inner insulator or > >> perhaps switch to parallel bonded magnet wire or go twisted pair. > >> True? > >> Or maybe I'm overlooking something. > > > Actually, you probably are. Try a non-progressive winding - count the > > number of turns, then go through the four cores putting on half that > > number of turns before coming back through the four cores putting on > > the rest of the turns in the same sense, so that the end of the > > coaxial cable emerges from same point as where the widing started. > > > At the moment you have a - very weak - external field produced by the > > imperfectly coaxial nature of your coaxial cable as it makes its way > > around the loop in the plane defined by the fours cores; with the non- > > progressive winding this loop is much reduced. > > > The "imperfection" does seem to be about 0.1% - a non-progressive > > winding might well give you your next factor of ten reduction. > > > Progressive versus non-progressive windings are discussed in Rayner > > and Kibble's "Coaxial AC Bridges" a.k.a."Tricks from the National > > Standards Labs". > > >http://www.amazon.com/Coaxial-AC-Bridges-B-Kibble/dp/0852743890 > > > They get mentioned here from time to time.
I've been thinking about it, and you might be able to do some good with less work. Setting the cores on edge, rather than laying them flat - as pictured - would reduce the are included in the loop that presumably is responsible for your leakage inductance. Twisting that loop could make the effective area even smaller. If we label the four cores as A,B,C and D and the present arrangement is A B you might do better with A B D C C D. Worth a try. Granting that this wouldn't be problem if coaxial cable was perfectly symmetrical, one could argue that the imperfections in symmetry that are messing you about are randomly distributed, and thus the re- arrangement can't be assumed to cancel the stray coupling. This may be true, but it is likely that bent coaxial cable isn't perfectly symmetrical in regular and reproducible way which would make the stray field more predictable and more likely to cancel. -- Bill Sloman, Nijmegen