[Amps] Resonant choke filter

[Angel Vilaseca]

Hi

peter.chadwick at Zarlink.Com wrote:

snip

> As Will said, tolerances mean that very careful choice of components is
> needed if you are to be certain that the choke is tuned HF: if you tune it
> LF, it will look like a lossy capacitor and the whole thing will revert to
> a capacitor input filter. If you get the wrong resonant condition, you can
> get enormous voltages built up too, so this is not an exercise for the guy
> who isn't experienced in working on HV circuits. Tom, W4JI, has a
> frightening story about that, which you'll find somehwere in the Amps
> archives. 

snip


> 73
> 
> Peter G3RZP


What could a wrong resonant condition be?

Resonance frequency can be 

-much too low (what happens then?)

-a bit too low just as you just wrote,

-slightly too high, which is what we want in this case

-way too high which is equivalent to a classical, non resonant choke

-exactly tuned to 120 Hz. In this case, we would have maximum AC at the
tuned choke capacitor terminals which could cause the voltage problems
you mention. However, since there is a bleeder included in the circuit
and copper and iron losses in the choke, the Q of the tune circuit
cannot be expected to be very high.

I have a vintage 800 V power supply with tuned chokes. The capacitors
are oil filled 2 Kv models. It works nice.

Someone wrote recently on this list about 3 times the voltage. That
would mean 2,4 Kv.

Can someone remember which problem Tom W4JI encountered?


73

Angel Vilaseca HB9SLV