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Step-up transformer design
Step-up transformer design
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Old 28th February 2010, 04:27 PM   #61
geraldfryjr is online now geraldfryjr  United States
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very nice.i have been trying to find a source for some of those big c cores. jer
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Old 28th February 2010, 04:41 PM   #62
Statics man is offline Statics man  Ukraine
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Quote:
Originally Posted by chinsettawong View Post
Hi Statics Man,

Thanks for sharing your transformer design.

Wachara C.
Glad to help you. Here are some more Photos.
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Old 28th February 2010, 05:38 PM   #63
JonasKarud is offline JonasKarud  Sweden
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Very nice transformer! I understand that you have a very good saturation
marginal with 99 primturns on a 10 square cm core.

The wheel that feeds the wire, is it moving by itself sideways?

And the counter, is it from a motorcycle?
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Old 28th February 2010, 07:44 PM   #64
bentl is offline bentl  Norway
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Default First winding attempt

Hi,

I just tried to wind my first transformer on a EI84 core. At first, all worked out as intended. I stoppet the winding from time to time to inspect and all was fine.

Then I ran the winding machine and passes 1500 "double turns" (winding with 2 strains of wire on the secondary) and stopped to inspect.


I saw that a turn had skipped the bobbin an coiled around the axle of the winding machine. Had to discard the whole secondary winding and start over...that will be an other day

On top of that, it seems like it will be a very tight fit to have 4800 turns on the secondary on that core. Aiming for a 1:120 ratio with 40 turns on the primary.

Regards

Bent
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Old 28th February 2010, 11:12 PM   #65
bolserst is offline bolserst  United States
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Quote:
Originally Posted by geraldfryjr View Post
second:the meter i have only reads ac average and not true rms which was throwing me way off from my scope readings.but the pics are true and i was getting 600v plus at 300hz and above and flat to 10khz with a drop to 20khz of not more than -1.5db,with only 10 turns for a primary

my study has found that a toroid power transformer will work very well to drive an esl by just winding a new primary to get a desired ratio.this will only work in a hybrid system unless you have a realy realy big core.
Hello Jerry,

Congrats on improving your measurement setup and getting things to match up better with your anticipated results.

Not sure if you caught Calvin's suggestion for you concerning your primary windings in post #159 on your other thread.
http://www.diyaudio.com/forums/plana...ml#post2087071

Basically, if you want to use the existing 120V windings as your secondary and plan to use a small number of primary turns, like 10, to get the step up ratio you desired (70, I believe) then the bandwidth will be limited on the low end by the resulting low inductance and possibility of saturation. On the high end, you are limited because of the poor coupling of the small 10 turn section to the 360 degree coverage of the secondary on the core.

Calvin's suggestion is to wind multiple section of 10 turns and hook them up in parallel. The primary inductance will be the same, so your low end impedance will be the same. Also, the step-up ratio will be the same. But, the leakage inductance will be reduced by approximately the square of the number of sections you put in parallel. Just adding one or two more sections should easily push your bandwidth above 20kHz even with the capacitive load of your panel added.

Give it a try, you will like the results!

Last edited by bolserst; 28th February 2010 at 11:14 PM.
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Old 1st March 2010, 12:00 AM   #66
geraldfryjr is online now geraldfryjr  United States
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thanks bolserst,yes i did, and i followed his advice.i have already made one data chart using my scope and as of this moment i'm making another one using my cheapy digital VOM to compare it too, i am also writing the process to post, hopefuly by tommorow.thanks again! jer

Last edited by geraldfryjr; 1st March 2010 at 12:17 AM.
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Old 1st March 2010, 01:49 AM   #67
chinsettawong is offline chinsettawong  Thailand
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Hi,

I also find out that by reducing the coil covering area from a full circle to half or a quarter of a circle on a toroid makes a lot of difference to high frequencies. I guess you can tailor the coil capacitance by adjusting the coil coverage area. With less area but the same number of turn, high frequencies can go higher.

Wachara C.
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Old 1st March 2010, 02:37 AM   #68
geraldfryjr is online now geraldfryjr  United States
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yes, i think i have noticed this.i wil investagate this further.my 10khz to 20khz seemed to go from -.9db to -1.25db or -1.6db or more.using all of 40 turns as 10 turns.i used .01 uf 6kv cap on one 120v winding in all of the test except the 10 turn one. because it presented less than a 8 ohm load above 200hz and the amp would shut down immediately at any voltage.
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Old 1st March 2010, 01:20 PM   #69
bentl is offline bentl  Norway
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Default New cores in order

Hi,

I found a local transformer manufacturer today who was more than willing to supply me with laminations, coilformers and the lot for a very modest charge!

laminations of type EI120/40 which is 120mm wide, with a core of 40mmX40mm

I guess this core will be big enough to hold 40 primary turns X 3 and 4800 secondary turns.

Regards

Bent
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Old 1st March 2010, 01:44 PM   #70
JonasKarud is offline JonasKarud  Sweden
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Quote:
Originally Posted by bentl View Post
Hi,

I found a local transformer manufacturer today who was more than willing to supply me with laminations, coilformers and the lot for a very modest charge!

laminations of type EI120/40 which is 120mm wide, with a core of 40mmX40mm

I guess this core will be big enough to hold 40 primary turns X 3 and 4800 secondary turns.

Regards

Bent
Is it grain-oriented iron? Remember that there is a huge difference in sound quality, especially in high freq's, between thick ordinary power transformer laminations and thin grain-oriented ditto!
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