Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Va rating reloaded
Va rating reloaded
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 27th October 2012, 07:36 PM   #1
Shelah is offline Shelah  Zambia
diyAudio Member
 
Join Date: Oct 2010
Default Va rating reloaded

Dear all,

I recently got a hold of a toroid trafo with unknown va rating. I had started a similar thread on this topic some time back but I have brought it again just to recap.
The trafo specs are as follows:

220v ac input
44-0-44 output
Weight 3.8 kg
Outer diameter 12.5 cm
Height 8.4 cm
Twisted pair of 1mm thick wires per 44 volt winding.

With these specs can you deduce an estimate of the va rating?
  Reply With Quote
Old 27th October 2012, 09:56 PM   #2
sreten is offline sreten  United Kingdom
R.I.P.
 
Join Date: Nov 2003
Location: Brighton UK
Hi, 300VA to 400VA is ballpark, rgds, sreten.
  Reply With Quote
Old 28th October 2012, 01:51 AM   #3
whizgeek is offline whizgeek  Ireland
diyAudio Member
 
Join Date: Feb 2010
is there a method where you measure up to short circuit current and decide a ballpark based on current/voltage drop ?/

i rarely ever buy a transformer, but don't have a method of measurement, so am interested
  Reply With Quote
Old 28th October 2012, 02:34 AM   #4
sofaspud is offline sofaspud  United States
diyAudio Member
 
sofaspud's Avatar
 
Join Date: Nov 2005
Location: San Antonio
A load regulation test will provide useful information, but I'm thinking a person could do pretty well just by comparing characteristics of the transformer in hand with those in a mfgr's catalog.
__________________
It is error only, and not truth, that shrinks from enquiry. - Thomas Paine
  Reply With Quote
Old 28th October 2012, 05:56 AM   #5
TonyTecson is offline TonyTecson  Philippines
diyAudio Moderator
 
TonyTecson's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
Va rating reloaded
coil dc resistances also give clues as higher rated traffos will have lower dc resistance in their windings...
__________________
planet10 needs your help: Let's help Ruth and Dave...http://www.diyaudio.com/forums/plane...ml#post5010547[B
  Reply With Quote
Old 28th October 2012, 11:26 AM   #6
AndrewT is offline AndrewT  Scotland
R.I.P.
 
Join Date: Jul 2004
Location: Scottish Borders
Secondary has a current rating of ~ 3.1A/mm^2
two off 1mm diam ~ 1.6mm^2
giving a current rating of ~4.8Aac
resulting VA~430
__________________
regards Andrew T.
  Reply With Quote
Old 28th October 2012, 12:50 PM   #7
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
You can get a rough idea by seeing how voltage drops with load, but you don't know whether the transformer is designed to drop 3%, 5% or 10% at rated load. You could apply a load and see how hot the transformer gets, but you don't know what is the max temperature of the internal insulation so again only a rough guide.
  Reply With Quote
Old 1st November 2012, 05:23 PM   #8
Shelah is offline Shelah  Zambia
diyAudio Member
 
Join Date: Oct 2010
t
hanks people.
Andrew T ,thats a good estimation.
Tony i did'nt get the primary resistance but my rough estimation should be 2.5ohms to 3.5 ohms. i will give the correct reading when i get home.

now that Andrew T has given his rough estimate, i have plans on using it on Apex audio's HV23 amplifier rated 350w 4ohms, 200w 8 ohms. is it worth the try?
  Reply With Quote
Old 1st November 2012, 06:16 PM   #9
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
Comparing weight is a rather useful way to decide rating.
Most toroid can be determined that way.
__________________
lineup
  Reply With Quote
Old 1st November 2012, 08:17 PM   #10
Ian Finch is offline Ian Finch  Australia
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour, NSW
Quote:
Originally Posted by Shelah View Post
..... i have plans on using it on Apex audio's HV23 amplifier rated 350w 4ohms, 200w 8 ohms. is it worth the try?
You probably realize that the HV23 is specified with 75V power rails but with your transformer, they will be considerably less at ~65V. The power may then be around 180W/8R and 300W/4R, allowing for voltage sag with such a small transformer. There are cheaper circuits suitable for this lower power.

There's not much point building such a large amplifier for pro. use when you plan to skimp on the power supply. It just makes no sense.
__________________
If only I had listened....
  Reply With Quote

Reply


Va rating reloadedHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
VA RATING Shelah Solid State 50 9th May 2012 09:00 PM
Toroidal VA rating Nate805 Chip Amps 11 15th November 2008 09:29 AM
Transformer VA rating Buzzy Parts 11 26th June 2008 10:13 AM
Transformer VA rating?? RyanW Power Supplies 6 11th November 2006 11:23 PM
Transformer VA Rating vs. Current Rating JhonDoe Chip Amps 45 5th June 2004 02:11 AM


New To Site? Need Help?

All times are GMT. The time now is 10:30 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki