On Thu, 2009-05-21 at 19:25 +0100, Steve Hunt wrote:
> That's not true of all baluns. The flux in the ferrite core of a 1:1
> Guanella balun wound with coax depends on the common-mode current, not
> on the differential-mode current; so it's not directly related to the
> load Z.
>
> Also, we shouldn't confuse heating with saturation. To quote W8JI: "We
> often assume heat means a core is very lossy or is "saturating", but
> *t*his often isn't true." " It is almost never core saturation, unless
> the core is subjected to very low average power and very high peak power
> levels."
>
> Steve G3TXQ
>
Nearly aways the balun on a tuner is a voltage balun and it is sensitive
to applied voltage. Voltage is what saturates the core through the
magnetizing inductance. With power applied, a high impedance gets high
voltage a low impedance gets low voltage. With a high impedance load its
more likely to saturate and thus heat the core. And when a core
saturates for part of a cycle the inductance of the winding goes way
down.
Its OFTEN core saturation when the core area is not chosen to be large
enough.
73, Jerry, K0CQ
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