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Re: [TCML] Terry filters




On Dec 30, 2007, at 8:53 PM, bartb wrote:

A Terry Filter can dissipate about 100 to 200 watts easily.

Each gap conduction must be added. For a Terry Filter or similar, consider the following:

P = 2 x 0.5 x C x V^2 x BPS

Now do the math.

You'll find it is still be low comparatively, but not quite as low as you are thinking.

I must be missing something. How can the current be any higher than feeding a dead short? At 120mA continuous, I'm assuming not just intermittent gap conductions, but actually more
as if the gap were shorting the transformer 100% duty cycle.

(unless you're running a resonant cap, something I'll never do, as I don't care to risk
my hard-to-replace 120mA NST)

Take care,
Bart




Bill Lemieux wrote:

On Dec 30, 2007, at 12:15 AM, Neal Namowicz wrote:

Hello everyone,
Just a question about terry filters, since the topic seems to be cropping up a lot lately. How much loss is there when using them? I'm no EE, but any time I see the main power coming in going through resistors, there must be some loss.

power dissipated in a resistor = the square of the current X resistance

So, for a TF with 1kΩ resistors, and a 15kV / 30 ma NST short- circuited by the spark gap, we dissipate 0.9 watts in the resistors, or 0.2% of the transformer's power.

With a 15kV / 120mA NST driving a short through the filter, we dissipate 14 watts, or 0.8% of the transformer's maximum power.

(somebody check my math, I'm still waking up this morning)

Also, are the TF's "one size fits all", or can the components be sized to correspond with how much potential power you have coming in? It seems that we endeavor to eliminate "lossy" components. "Using beer bottle caps? Replace them with an MMC." Don't use a dimmer switch, too "lossy", etc. Ultimately, is using a TF a trade- off between loss and protection? Kind of like driving a newer car that comes with a mandatory explosive device (air bag) in the steering wheel. "But it's for your protection!" Just one of a number of reasons my two vehicles are 1964 and 1980 Chevys. The k.i.s.s. principle, and no bombs staring me in the face. But I digress, sorry. So, what do you think about the terry filters?

Neal.

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