On 7/6/16 12:31 AM, Steve Hunt wrote:
Note what I said about duty cycles!
I would think that most ham use is a low duty cycle operation (leaving
you EME and RTTY contesters aside): saturation (and magnetization) is
purely a peak level thing. You could saturate a core in a single cycle
(or dit, or on a short voice peak), and you'd not see any appreciable
heating.
I wonder if anyone has ever had a core ruined by a lightning impulse?
Steve G3TXQ
On 06/07/2016 00:00, Richard (Rick) Karlquist wrote:
On 7/5/2016 11:00 AM, Steve Hunt wrote:
Do the maths on saturation - you'll find that core overheating occurs
well before saturation for the duty-cycles typical of Ham operation.
To quote Amidon: "Overheating of the core will usually take place long
before saturation in most applications above 100kHz."
Steve G3TXQ
This generalization is valid for cores with an air gap and
powdered iron cores (which essentially have a built in air gap).
It most definitely doesn't apply to closed gap ferrites,
such as toroids. One dit can not only saturate them, but
actually magnetize them. I have actually done this, accidentally,
when I tried to use a current transformer and the secondary
was unloaded. It was something of a corner case since the
primary of a current transformer is only 1 "turn".
Rick N6RK
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