Re: Toroid ballast design

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Conner <steve@xxxxxxxxxxxx>


> I dont know where these cores saturate and if 24600 gauss is no 
> problem, the fewer number of turns will mean less winding loss.

I've heard that 17000 gauss is about where transformer iron starts to 
saturate. Commercial transformer designs seem to aim for about this 
17kG peak figure. 24600 seems a bit "Out there" :-o

One handy rule of thumb I heard when designing gapped ballasts is 
that gapping the core doesn't change the volt-second capability. (To 
a first order at least.) So the number of turns you need to avoid 
saturation is the same as for an ungapped transformer. Hence a good 
starting point with a gapped variac core would be "The same number of 
turns as the variac had".

I guess with two stacked cores, you only need half the number of 
turns, or is it 1/sqrt(2)?

Steve Conner
http://www.scopeboy.com/