zobel network as snubber in HV acdc supply

kenez · « **on:** 16 Mar 2005, 09:33 pm »

Can we use a Zobel-network neutralizing the leakage inductance of the PT as an RF-snubber circuit? With high-voltage supplies (for tube B+) the equivalent resistance of the power transformer is in the range of few hundred ohms. Since the capacitor in the Zobel network is Lleak / R^2 it will be a reasonable value because of the high R.

hagtech · « **Reply #1 on:** 17 Mar 2005, 03:14 am »

Zobel? Sure. But it is already in there! You didn't specify which product, but they all have a zobel snubber network on the secondaries. Even the 6V winding has the snubbing resistor (capacitor so large I just left it out, as power dissipation was not an issue).

All supplies snubbed and damped already. The chokes are series snubbed (not parallel) and tuned with loading capacitance for Bessel-type filter response (no peaking).

jh

hagtech · « **Reply #2 on:** 17 Mar 2005, 06:06 am »

Ok, ok. So it's technically not a Zobel, but it looks like one. A Zobel is an impedance matching circuit - to transform a given complex impedance into a pure resistance over all frequencies. But we're not really interested in impedance matching, instead we want to snub the parasitic resonance. That's a different thing. And the snubber values calculate out differently.

Not sure if changing to a Zobel will do any good, could burn huge amounts of power and suck down the output voltage (maybe in half?).

jh

kenez · « **Reply #3 on:** 17 Mar 2005, 04:22 pm »

Thanks for the answer. It's not about one of your products, I just read your excellent pdf ('Calculating Optimum Snubbers') about the topic and the Zobel thing came to my mind.
I'll check the voltage reduction.