[TCML] pulse cap specs
jimlux at earthlink.net
Fri May 23 08:20:25 MDT 2008
Yurtle Turtle wrote:
> I run my pig at 280 in, yielding 16.8 kV out. My safety gap is set
> just above that. I run my MMC (Multi Maxwell Cap) at five strings of
> two, or 75 nF 70 kV.
In that case, you'd expect pretty good life. 16.8 kV (rms?) is about
23.5 kV, call it 24 kV. Compared to the 70kV rated voltage for the
caps, you're about a factor of 3 undervoltage.
Using the formula from Maxwell
Lx = Lref * (Qref/Qx)^1.6 * (Vref/Vx)^7.5
Qref is the Q for 50% VR (which is what the cap is rated for) or about 2
Qx is what your tc is running at perhaps 10-15.
(2/15)^1.6 * ( 3)^7.5 = 0.03 *3800 = over 100 times the life...
> --- On Thu, 5/22/08, Jim Lux <jimlux at earthlink.net> wrote:
>> From: Jim Lux <jimlux at earthlink.net> Subject: Re: [TCML] pulse cap
>> specs To: "Tesla Coil Mailing List" <tesla at pupman.com> Date:
>> Thursday, May 22, 2008, 8:46 AM Yurtle Turtle wrote:
>>> These caps hold up just fine in Tesla duty. I've
>> got ten and have
>>> never had a problem, even when pushing them over 400
>> bps. The spec
>>> sheet says they're good to 500 pps. The only
>> problem is that you
>>> don't know how much abuse they'veseen before
>> you buy them. Keep in mind that pulses/sec is not breaks/sec, at
>> least as defined by the cap mfr. A TC typically runs at almost 90%
>> reversal, which is a lot harder on the cap internals than the 20%
>> or 50% often spec'd in the capacitor data sheet in connection with
>> the life spec.
>> OTOH, reducing the voltage across the cap by a factor of two has a
>> HUGE effect on life.
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