Obviously paralleling gives you lower primary winding resistance thus lower lose/heating. vax, 9000 On 9/1/06, Chuck Guzis <cclist at sydex.com> wrote:

In a lot of cases, the limiting factor is the primary winding (often when a transformer burns out it's the primary the fails). So yes, I would paralelle up both sets of windings. Is there a reason not to? Again, is there a reason no to? -tony

On Friday 01 September 2006 03:01 pm, Chuck Guzis wrote: I would have to say that the exact answer to that would depend on the design of that particular transformer, but it would seem to me that pretty many of them that I've looked at are limited by the primary winding, particularly when it comes to output current, so if it were me I'd use them both. You could always apply some load to the secondary and try it both ways, increasing the load until some particular voltage drop happened. I seem to remember some discussion in the yahoo "electronics_101" group about this very subject a while back. Measuring the open-circuit voltage first, you'd want to draw current until you got no more than a 10% drop or so, and while doing that make note of just how warm that transformer is getting. Try this with one primary winding, and then with both, and that should give you a pretty definite answer. I also saw some stuff in the above-mentioned group that gave some rough idea of what sort of output current you might expect out of a given transformer by looking at the cross-section of the core. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin