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Phil Allison[_3_] Phil Allison[_3_] is offline
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Default Overvoltage protection


"Alex Pogossov"
"Phil Allison"
"Alex Pogossov"


In any case, an abrupt interruption of the plate current will cause a
voltage spike on the OPT primary. The stored magnetisation energy of
Lp*(Ia^2)/2 will have to be dissipated. Lp can be quite high in a decent
amp. If a load is connected, then the energy will be dissipated in the
load giving you a loud crack in the speaker. A residual smaller energy
stored in the leakage inductance Ls*(Ia^2)/2 will most likely be safely
dissipated in a snubber of say 2200pF+5K usually connected in parallel
to the OPT primary.

But what is the load is not connected? Then the huge magnetisation
energy



** Why huge ???

If Lp is say 100H and Ia = 0.1A then how many Joules is that ?


Apparently 0.5J.



** IOW - **** all.

Even the smallest Varistor you can buy will absorb it with ease.

Like this one for $ 1.58 + gst

http://au.element14.com/epcos/b72205...9?Ntt=100+4399


..... Phil