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Registered Member #2148
Joined: Tue Jun 02 2009, 02:22AM
Location:
Posts: 62
hi i started firing up this coil lately and pleased with the results (maybe?) im getting 31" aprox. spark length with no ground target. still this coil is yet tuned and needs more fine tuning. any tips about tuning tesla coils? can i really achieve 50" sparks based on my calculations in javatc? specs: 15kv@60ma sucker gap 3x12 spun aluminum toroid 0.015 uF CDE caps (0.023uF when measured using multimeter..WHY!?) 4.5"x18" 25awg secondary tap at 9th turn primary. LEDs giving off a lil light without power. anyway heres the video.
Registered Member #2390
Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381
Check the tolerance on your caps. You can do the math including the tolerance and see if that is the reason you measure .023uF instead of the marked .015uF Nice video! That is a very sweet little coil, nice work!
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
electrons - I believe Eniyuki is talking about the capacitance value of his entire MMC assembly, not the value of a single capacitor. If I recall, he used C-D 942C20P15K capacitors, which are rated at 0.15uF, not 0.015uF.
Eniyuki - I suspect measurement error. What type of instrument are you using to make your capacitance measurements? What is its rated accuracy on the capacitance range you are using? Also, do you have bleeder resistors across each capacitor?
I have a quantity of unused C-D 942 caps, 0.15uF at 2,000V from several different C-D manufacturing lots (different date codes). I measured 25 parts using a laboratory-quality Fluke 87-III multimeter, which allows "zeroing" out of the test lead capacitance.
Of the 25 parts measured, the highest value was 0.151uF, and the lowest value was 0.149uF.
This is very small part-to-part variation in capacitance value, and shows very good manufacturing process control.
Registered Member #2148
Joined: Tue Jun 02 2009, 02:22AM
Location:
Posts: 62
Herr Zapp wrote ...
electrons - I believe Eniyuki is talking about the capacitance value of his entire MMC assembly, not the value of a single capacitor. If I recall, he used C-D 942C20P15K capacitors, which are rated at 0.15uF, not 0.015uF.
Eniyuki - I suspect measurement error. What type of instrument are you using to make your capacitance measurements? What is its rated accuracy on the capacitance range you are using? Also, do you have bleeder resistors across each capacitor?
I have a quantity of unused C-D 942 caps, 0.15uF at 2,000V from several different C-D manufacturing lots (different date codes). I measured 25 parts using a laboratory-quality Fluke 87-III multimeter, which allows "zeroing" out of the test lead capacitance.
Of the 25 parts measured, the highest value was 0.151uF, and the lowest value was 0.149uF.
This is very small part-to-part variation in capacitance value, and shows very good manufacturing process control.
Regards, Herr Zapp
herrzapps right i measured the total capacitance of my MMC. im using a digital multimeter. dont know the brand but not as sophisticated as fluke. i measured 1 cap and reads .151uF i put a bleeder and measured it again and now reads .233uF
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Yea, bleeder resistors will change the capacitance. Idk how 10megohms is enough to change it *that* much :P.
A dead capacitor would raise the capacitance in a series string, and a capacitor that failed, then 'healed' would have lower capacitance. Not sure if either is the case, though.
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Arcstarter -
"A dead capacitor would raise the capacitance in a series string, and a capacitor that failed, then 'healed' would have lower capacitance."
It might be more accurate to say that a "shorted" capacitor would increase the capacitance of a series string, and that a capacitor that had had been severely overvoltaged many times, and had suffered dielectric punctures with "clearing" and loss of electrode area, would decrease the capacitance of a string.
In Eniyuki's case, the inaccurate capacitance measurement of his MMC is due to the effect of the bleeder resistors in parallel with each capacitor.
Registered Member #2148
Joined: Tue Jun 02 2009, 02:22AM
Location:
Posts: 62
thanks Herrzapp for clearing things up but both of you seem clear to me. ANYWAYS
i uploaded a new video of my coil i think it is tuned because streamers became longer and THICKER 36" streamer, 41" ground target is this coil already achieving its optimum performance of 900 watt PSU? or no?
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Eniyuki -
Great job! That is a beautiful piece of work, and the performance is very good.
This is a perfect example of the results that can be obtained by taking the time to do the required research, and then assembling the coil with craftsmanship and attention to detail.
A few questions: 1. What is the strip of aluminium foil on the floor to one side of the coil? Is this a counterpoise? 2. If the aluminium foil is not a counterpoise, what are you using as an RF ground? 3. What is the gap spacing that you are using in your sucker gap? 4. What is your next step with this coil? More tuning, more input power (another NST), or ???
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first light :) 900w coil
