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tmblack 21st January 2005 04:08 PM

Winding Your Own Transformers
 
Has anyone tried to wind their own power transformers?
I'm considering a 120V to 50VCT transfomer @5A.
I have some EI cores of M4 steel, 1.5" center tougue and 5" long.

Anyone know the proper method to do this?

Regards,

Tom

sss 21st January 2005 04:48 PM

few tips :)
first u gotta find a core that can handle that power (500VA) and got enough space for the windings
most of the time u can use a core taken from 500VA (or more)transformer
also its much easier if u allready got the primmary coil (suited for 120V)
if u got all of the above , winding the secondaries wount be a problem

tmblack 21st January 2005 05:53 PM

I already have the core as mentioned above. Not sure how to calculate the maximum VA rating for it but it but I can stack up the laminations(it does have to be square).

I just threw a number for the current but 5Ax50V should only be 250VA, not much for its size.

Tom

sss 21st January 2005 06:19 PM

50V @5A ct = 500VA(each secondary 250VA)
or maybe u meam 25-0-25 :rolleyes:
an oversized core is not so good, u will use longer wires=higher output resistance
if u got no primary coil u gotta calculate the number of turns for 120V operation , i dont remember the formula for this :o

Stocker 21st January 2005 11:59 PM

Somebody wants you to do this... I found this earlier today...
Roll your own power transformers

Do let us know how it turns out!

jackinnj 22nd January 2005 01:42 AM

here;s an article from a magazine which went bust about a decade ago:
http://www.tech-diy.com/rewinding_transformers.htm

Sch3mat1c 22nd January 2005 02:35 AM

*Sch3mat1c wonders where Geek is :confused:

Lesse, http://geek.scorpiorising.ca/windingtransformers.html seems to be the one. :)

Your core sounds about right. You want to use a core somewhat oversized so you don't run out of room when you're almost done with the windup. :D Too large a core is just a waste of good core material.

Don't worry about resistance. A good transformer will barely get warm. For 5A, you'll want around 16-18AWG copper wire.

Tim

Sch3mat1c 22nd January 2005 02:53 AM

Quote:

Originally posted by sss
50V @5A ct = 500VA(each secondary 250VA)
or maybe u meam 25-0-25 :rolleyes:

CT always means the full voltage winding is split, so 25-0-25 would be accurate. However, given power factor of a capacitor input filter, a 500VA (i.e., 10A RMS) rating may be advisable.

Quote:

if u got no primary coil u gotta calculate the number of turns for 120V operation , i dont remember the formula for this :o
A book I have gives it as E = F * H * N * A * 4.44 x 10^-8, with E in volts, F in Hz, H in "lines of flux per square inch" (1 tesla ~= 60,000 lines; a good value is 50-80k), N is turns and A in square inches (cross section of the center of the core, which the turns are wrapped around). With some algebra you can find whichever you need.

Looks like you'll need about 300-350 turns for the primary.

Tim

tmblack 22nd January 2005 06:53 AM

Gentlemen,

thank you for the assistance. I'll try my best to get something done.

Tom

AJT 10th April 2010 08:02 AM

Quote:

Originally Posted by tmblack (Post 557186)
Has anyone tried to wind their own power transformers?
I'm considering a 120V to 50VCT transfomer @5A.
I have some EI cores of M4 steel, 1.5" center tougue and 5" long.

Anyone know the proper method to do this?

Regards,

Tom

50v @5amps is 250Va, but primary VA needs to be around 350va.....looks like a 1.5 inch center leg stacked to 2.5 inches height is good.

primary turns of about 280 of ga #19 using grain oriented silicon steel, more if not using goss...

secondary turns of 120 #14 split into 2 coils of 60 turns each...wired in series to get the center tap.

you have to find out your coil buildup and adjust turns or wire size to fit into the window of your EI cores.

if you can get hold of a bobbin, then scramble winding is easier to do... you only need to worry about primary and secondary coil insulations.....


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