[Amps] Re: Transformer in GLA 1000 B : OK for 2xGI 7 ?

[craxd]

David,

You can "kind of" go by those charts. Really, the core has to be sized 
by several factors more than the weight. It's according to what type of 
circuit they'll go in, the frequency, duty cycle, heat dissipation, etc. 
Actually, the power of a transformer is determined by the area of the 
cores center leg which is inside the coil. The weight around the outside 
can change. 1000 watts takes about 5.6 sq inches if I recall and 2000 
takes about 7.25 sq inches. This is measured by the width of the tongue 
and the depth of the stack. The weight of the wire is not included in 
his calculations, only the core weight itself. The weight of the 
hardware is negligible but isn't included either. I never could figure 
why Bill Orr just showed that and did not include any actual formulas 
for determining the core and the number of turns.

Will Matney

 >>
In the old Bill Orr Radio Handbooks, he presents a graph of transformer core
weight vs. power capacity for various duty cycles.  Admittedly it is an
approximation with a couple of caveats for ICAS service; low breeder
resistor load and cut off bias on the tube during stand by.  The graph
discloses that you can get 2 KW from a core weight of 22 pounds if you want
to push it, or 35 pounds if you want to be a more conservative.  Although it
does not state explicitly, I assume that the weight of wire is included in
the core weight.  The core weight does not include the case or mounting
fixtures.

The statement is made that the data are the results of extensive testing on
typical transformers.

David C. Hallam
KC2JD