Winding your own toroid is very difficult. Commercially they use very specific winding machines - it's not like hand winding an E - I core. Why do you need a special transformer - isn't there an already available model? Even putting two transformers into one chassis would be easier than having one custom wound, although most manufacturers will do a prototype - for prototype prices.
But toroidal transformers that don't rattle or buzz aren't something I'd attempt to DIY.
But toroidal transformers that don't rattle or buzz aren't something I'd attempt to DIY.
Posted by djk on May 2, 2001 at 07:20:59
In Reply to: Re: Eddy current in toroidal transformer. posted by Steve Eddy on May 2, 2001 at 03:38:00:
The only toroids that use powdered cores are the ones used with switching supplies as found in car stereo. Toroids for 50~60hz use the same steel stock E-I types use. It comes off of a coil and is cut to length, wound into a core, the ends spot-welded, the edges radiused on a lathe, and then annealed in an oven. The core is then taped and the primary wound and taped again. When you order it, the secondary is wound and taped again. The manufacturer can offer hundreds of different "customs" and only stock a few different VA cores primary wound and ready to go.
In Reply to: Re: Eddy current in toroidal transformer. posted by Steve Eddy on May 2, 2001 at 03:38:00:
The only toroids that use powdered cores are the ones used with switching supplies as found in car stereo. Toroids for 50~60hz use the same steel stock E-I types use. It comes off of a coil and is cut to length, wound into a core, the ends spot-welded, the edges radiused on a lathe, and then annealed in an oven. The core is then taped and the primary wound and taped again. When you order it, the secondary is wound and taped again. The manufacturer can offer hundreds of different "customs" and only stock a few different VA cores primary wound and ready to go.
You can buy toroid with the core and primary completed.
You only have to add on the secondaries to give you a custom build.
But even this is not cheap.
They charge more for a secondaryless, than for a completed and tested and guaranteed whole toroid.
Winding a toroid is only feasible if it is low voltage (fewer volts) and a bit easier if it is big (fewer turns per volt)
You only have to add on the secondaries to give you a custom build.
But even this is not cheap.
They charge more for a secondaryless, than for a completed and tested and guaranteed whole toroid.
Winding a toroid is only feasible if it is low voltage (fewer volts) and a bit easier if it is big (fewer turns per volt)
Are you familiar with the formula:
Vpri/Vsec = TurnsPri/TurnsSec
That gets you the ratio of turns.
Are you familiar with 3Amperes/square millimetre of wire cross section.
That gets you to wire size.
Use both to design the open circuit voltage of the transformer.
Then apply a guessimated transformer regulation to arrive at a operating voltage.
BTW.
Test the primary only current draw for the full range of your mains supply.
If the primary has too few turns you risk saturation during periods of high mains voltage. You must avoid saturation.
Vpri/Vsec = TurnsPri/TurnsSec
That gets you the ratio of turns.
Are you familiar with 3Amperes/square millimetre of wire cross section.
That gets you to wire size.
Use both to design the open circuit voltage of the transformer.
Then apply a guessimated transformer regulation to arrive at a operating voltage.
BTW.
Test the primary only current draw for the full range of your mains supply.
If the primary has too few turns you risk saturation during periods of high mains voltage. You must avoid saturation.
Putting a new custom secondary on a toroid is relatively easy - I do it all the time. 500-1000 VA toriods with secondary voltages too low to be useful come up all the time for $20-30. You can put 'em in series, add windings, replace entire secondaries. For safety, never rewind a primary yourself or re-use wire. The old wire can be re-used where insulation integrity is not a safety issue - like for speaker crossover coils.
Hi prtk;
I see that you have had responses to your project from people who have proven themselves both knowledgeable and helpful. I have no transformer design expertise but I have a thread in the Solid State section of this forum; " Toroidal Transformer Noise".
FYI; I have seen a 'youtube' video of someone making a toroid using recycled core material from another toroid. In my opinion, the acquisition of all the proper materials, proper assembly, questionable performance results, and my concern at the moment; noise, makes this a project to avoid.
I see that you have had responses to your project from people who have proven themselves both knowledgeable and helpful. I have no transformer design expertise but I have a thread in the Solid State section of this forum; " Toroidal Transformer Noise".
FYI; I have seen a 'youtube' video of someone making a toroid using recycled core material from another toroid. In my opinion, the acquisition of all the proper materials, proper assembly, questionable performance results, and my concern at the moment; noise, makes this a project to avoid.
I am using some 50VA 230/6v toroids in reverse for ESL stator stepup ... but I have found a problem .. I need 4 of them in series/parallel config to get the turns ratio to 1:153 . - What would happen if I removed turns from the original secondary , as in increase the turns ratio ? - another words , if i remove half of the secondary turns so to make 230/3v , then I would only need two toroids in series to get 153 ratio . But , what is the effect on the freq response and the saturation possibilities below 50hz .. as I have suspected saturation issues already . - im getting keen on pulling the insulation off and removing turns .
Thanks - yes , ive just found it . Calvin has written some great stuff . thanks . Im trying to find out why my amp clips so easily with bass - im not sure if its the 4 toroids in( primary parallel config ) or the bass is saturating the toroids themselves. - I did get better results on a much more powerful amplifier - so it may be more the low impedance load of having 4 primaries in parallel . - I will try series the primaries to detect the difference in quality . the level / ratio will of course be down. - im using 230v/6v duals . - RS Component 671-8959
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