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Old 28th March 2010, 09:29 PM   #1
Klimon is offline Klimon  Belgium
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Default Filament winding wire diameter

What wire diameter should I use for adding a 3A filament winding to a power xfmr? The load requires 6,3 volts (=20 turns).

Thanks!!

Simon
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Old 28th March 2010, 09:44 PM   #2
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You can calculate.....2.5 A for 1 sq. cm.
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Old 28th March 2010, 09:49 PM   #3
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Here is one that I found. Max values.
Solid core, 0.6mm @ 1.5A
1mm @ 3A
1.7mm @ 4.5A
2mm @ 6A
That is diameter of the conductor, there are American Gauge to Millimeter conversion tables available.
Doing a two to one safety margin I would opt for the 2mm version for your 3A load.

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Old 29th March 2010, 06:05 AM   #4
Klimon is offline Klimon  Belgium
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Thank you. Are the quoted values for OFC? If not, am I right to suppose that ~1/2 diameter thickness should suffice given OFC's lower resistance?

PS Not trying to be difficult, just trying to use parts on hand!

Happy building

Simon
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Old 29th March 2010, 02:25 PM   #5
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The values I found are from 'Morgan Jones, Valve amplifiers First edition?' Morgan Doesn't cite a footnote for these values so I will assume the "standard", 'common' copper conductors. Forgive me my ignorance but is OFC 'Oxygen free conductor'??? I thought "Oxygen free" refers to the insulation cladding being applied in an oxygen free environment. An attempt to keep the conductor/insulator interface from acquiring corrosion. As such does it have a "better" conducting value keeping conductor values constant?
I think there are other factors at play when winding different diameter windings independent of turns.....not to mention filling up the "window" in the I/E frame.

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Old 29th March 2010, 03:13 PM   #6
AndrewT is offline AndrewT  Scotland
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transformers are often wound with copper areas that give ~3A/sqmm

on this basis :
1mm diam= 0.785sqmm = 2.4Aac.
1.4mm diam = 1.54sqmm = 4.7Aac.
1.6mm diam = 2.01sqmm = 6Aac.
2mm diam = 3.14sqmm = 9.4Aac.

The resistance of pure copper is near enough the same as oxygen free copper.
The area required for the same voltage drop and for the same power dissipation is the same.
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Last edited by AndrewT; 29th March 2010 at 03:15 PM.
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Old 29th March 2010, 07:56 PM   #7
Klimon is offline Klimon  Belgium
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Quote:
Originally Posted by Richard Ellis View Post
The values I found are from 'Morgan Jones, Valve amplifiers First edition?' Morgan Doesn't cite a footnote for these values so I will assume the "standard", 'common' copper conductors. Forgive me my ignorance but is OFC 'Oxygen free conductor'???
I think there are other factors at play when winding different diameter windings independent of turns.....not to mention filling up the "window" in the I/E frame.

__________________________________________________ _____Rick....
Should have checked with old Morgan...

Oxygen-free copper - Wikipedia, the free encyclopedia

@ Andrew: thanks a lot! This is very helpful

Cheers - Simon
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