On Tue, 06 Oct 2009 06:25:53 GMT, Owen Duffy wrote:

Of course, one would hope that the transformers do lose heat to the
environment, and that would substantially slow the rate of rise of
temperature.

Hi Owen,

This opens another topic of my study with Thermal Resistance. One
paper that I have filed away that may aid you is W.E. Hord's "Recent
Developments In The Average Power Capacity Of Rotary-Field Ferrite
Phase Shifters." It may lack the specific application discussed here,
but it covers the math and interface relationships. Sorry, but I
don't have any publication details except for author/title.

Hord's work is with ferrites capable of sustaining RF power levels in
multiple KW. My first experience with ferrites (ca. 1972) was with RF
transmission line source/load isolation in the microwaves (the paper
is S-Band), a field that is wholly alien to discussion here.

73's
Richard Clark, KB7QHC