Help with rewinding a transformer - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 20th October 2010, 12:58 PM   #11
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
there are a lot of folks out there diy'ing their own traffos, i am pretty sure they must be doing it right....
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 20th October 2010, 11:53 PM   #12
diyAudio Member
 
Join Date: Apr 2010
Location: seattle, wa
I plugged OP's core area into my spreadsheet and i'd estimate that his core weighs 3Kg so i think he's off by a factor of ten somewhere.
certainly a lot bigger than a 15-30va transformer, which would require about 1200-2000 turns on the primary
  Reply With Quote
Old 21st October 2010, 12:47 AM   #13
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
for low grade cores, 1750 turns per square inch of core area is what i go by.....
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 21st October 2010, 01:18 AM   #14
diyAudio Member
 
imfree707's Avatar
 
Join Date: Oct 2010
Location: Tenn Loop Ranch, Lebanon, Tn.
Send a message via Yahoo to imfree707
Default Excellent Reference Info!

Quote:
Originally Posted by santonel View Post
So yeah, I'm kind of a newbie but I'm working on rewinding a transformer I had lying around. It's an EI transformer with a plastic split bobbin and it's original output was stated at 12-14.4v at 1.8A. So it's around 20 - 25VA ....snipped....
The information in the link was perfect and I bookmarked it for my future
use, thanks for the link! Your transformer, if stated V and A are correct,
is about 25va. Typical EI cores of that size do need about 10 turns/volt.
The author's technique of overwinding 10 turns, measuring the voltage,
then dividing by 10 to get turns/volt works every time. I tend to be
somewhat ADD, so I check my numbers a few times to be sure. A great
safety procedure is to use highest ohms setting on a multimeter to verify
pri/sec and pri/frame isolation, then apply power to the unloaded
transformer through an incandescent light bulb of equal or slightly lower
watt rating than the va rating of the transformer. The bulb should glow
dimly, if at all. A well-built transformer with a low-loss core will not cause
the bulb to glow visibly, but will almost always warm the bulb's outer
surface.
  Reply With Quote
Old 21st October 2010, 02:12 AM   #15
diyAudio Member
 
Join Date: Apr 2010
Location: seattle, wa
measuring the resistance from primary to secondary to core should be in the gigaohm range... or hundreds of megs for larger stuff.

@bob91343

transformer ratings are dependant on both core area and window area.

today it is best to throw most of those old rules of thumb out.

toss a test coil on it, measure the iron loss with a good wattmeter (kill-a-watt meters need to be calibrated, don't take them at face value below 40 watts!) , subtract the copper loss from the readings with a dc test.

core to copper loss ratio should reflect the average power to peak power ratio to minimise cost and and your electric bill, there is no reason to run it 50-50 unless its running full load 24-7
  Reply With Quote
Old 20th August 2013, 07:02 PM   #16
diyAudio Member
 
Join Date: Mar 2013
Location: trichy
sir please help me transformer rewinding in secondary(30/0/30v,5A),(0,14V,5A)and(12/0/12v 1A) primary 230V,50HZ AC how to calculate in primary and secondary turns and core size and bobbin size
  Reply With Quote
Old 21st August 2013, 03:47 PM   #17
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
wind on 10 turns.
Power up and measure the Vac of those 10 turns.

Then calculate how many turns to get your 30Vac, 14Vac & 12Vac.

Remember that you will be measuring open circuit voltages. The actual voltage under load on each of the windings will vary with the loading.
You decide how many extra turns on each winding to give the required loaded voltages for your circuit loadings.
__________________
regards Andrew T.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Transformer rewinding material elseif Parts 2 5th September 2008 01:30 AM
Rewinding Power transformer ThSpeakerDude88 Tubes / Valves 11 27th August 2007 03:07 AM
Bad transformer rewinding ostie01 Solid State 16 18th May 2006 10:08 AM
Rewinding Microwave Transformer 6502dude Power Supplies 5 3rd April 2005 05:06 PM
Transformer Rewinding JhonDoe Parts 3 1st March 2005 01:15 PM


New To Site? Need Help?

All times are GMT. The time now is 07:04 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2