OK ... I'm going to make this simple for you. Picture a material (like
a capacitor) with a lossy dielectric, and then apply a high RF voltage
across it. The dielectric passes a current as the result of the
voltage, and the lossiness of the dielectric generates heat. With a lot
of voltage the heat generated can be considerable.
Now then, whether you want to acknowledge it or not, a ferrite core IS a
lossy dielectric and can get hot when you put a high enough RF voltage
across it INDEPENDENT OF THE CURRENT FLOWING THROUGH THE WINDING AROUND
THE CORE. You can find innumerable references to the dielectric losses
of ferrite materials if you just bother to do some internet searching.
This is NOT an insulation breakdown issue ... not at all.
All of this can happen as soon as power is applied to the system
containing the ferrite. Certainly the rate of temperature rise will be
dependent upon how much voltage is applied, the frequency of it, and the
dielectric loss characteristics of the particular ferrite, but VSWR is
the voltage we're talking about here and that becomes relevant
immediately upon application of power.
I suspect that you will dig in your heels and continue to dispute this
basic physics, but at least I hope others here will understand things
better than you do.
Dave AB7E
On 9/2/2020 5:52 PM, Adrian wrote:
I say that your response is completely false and you are missing basic
electricity facts. The high voltage becomes an issue when insulation
breaks down, and then *current *starts
to flow through the fault path converting to emf & heat directly and
via induced current resulting ; P = E X I*. *Without the current the
heat does not occur, it is basic physics, and
the heat is directly proportional to the current. Voltage can exist
without current, but current cannot exist without voltage. Heat
produced is directly proportional to the current whether
it be in the intentional circuit path, or fault path caused by high
voltage insulation breakdown..
In addition, your statement that only current in the balun circuit
can produce heat is completely false. High voltage RF can create
major core heating due to dielectric losses in the ferrite core
independent of the magnitude of current flow in the tuning circuit.
Several discussions on the TowerTalk reflector have pointed this out
over the years for baluns and common mode chokes in ham radio
applications.
Dave AB7E
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