Re: final prep of coil
Subject: Re: final prep of coil
Date: Tue, 10 Jun 1997 11:47:36 -0500
From: "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
> Date: Sat, 07 Jun 1997 19:43:02 -0500
> To: tesla-at-poodle.pupman-dot-com
> Subject: final prep of coil
> From: Tesla List <tesla-at-pupman-dot-com>
> Subject: final prep of coil
> Date: Sat, 07 Jun 1997 12:57:40 -0400
> From: Michael Bauer <mbauer-at-execpc-dot-com>
> To: tesla-at-pupman-dot-com
> That last couple weeks I have made much progess on my latest coil. I
> done rough tuning but need to finish my grounding system and disconnect
> few ham radio antennas. My yard is really limited in size here in town,
> only low power settings will be used until I transport it up to my
> "cabin up
> north". Part of the fun in this project was building a good power
> cabinet. I loaded a full height 19" rack cabinet with a TEK scope,
> relays and time delay relays, electronic sampling of voltage and current
> nodes, SCR DC motor control for the RSG, variac panel with cooling fan,
> In the tuning tests I found out the I get resonance just at the end of
> primary coil. I may need to add another turn or two of tubing if I
> to a larger toroid. Here are my coil specs, and if anyone has questions,
> feel free to ask.
> primary coil: 6 3/4 turns of 1/2" copper tubing, spaced 1.375", with 22
> " ID.
> Primary cap: (two) 0.2 uf/20 kvdc caps in series for 0.1 uf/40 kvdc (I
> need to upgrade voltage rating here)
> RSG: 3600 RPM DC motor, 3/4 Hp, belt drive to spindle mounted 12" disk
> 12 studs on 10" circle. Studs are 5/6" brass, fixed electrodes are 3/8"
> stainless. DC motor SCR speed controller is 0 - 90 vdc with reversing
> relays and start/stop input. Speed is controlled by a pot for any speed
> between 0 and 3600 RPM.
> Secondary coil: 20" OD by 40" tall, wound on wooden form. Three plywood
> disks support 1/2" X 1" slats open spaced around perimeter. Slats are
> and doweled to disks. About a third of the wire is supported by slats,
> rest of the perimeter is air spaced. 17 turns per inch, or about 675
> Final tune with toroid is 66 Khz.
> Toroid: 6" by 30" aluminum ducting covered in aluminum tape. Center is
> covered plywood. Ends of duct were first hot melt glued together before
> Transformer: 10 Kva pole pig, 2 insulating electrodes on secondary.
> Kv/25.3 Kv depending on internal HV connections. I made a safety gap
> assembly that mounts to the output studs that allow easy setup for Jacob
> ladder demo's.
> Ballast: 140 amp welder with manual taps for low volt current side.
> variac: 240 vac/16 amp. Not nearly big enough but I am fan cooling it
> a large squirrel cage fan until it blows or I find a cheap replacement.
> Conrol panel: Low voltge relays, start/stop buttons, and indicators for
> power up sequencing. I added time delay lockouts between powering the
> and pig power to give the motor time to spinup (10 sec). Main contactor
> 100 amp rated.
> Instrument panel: Volt and current measurements of many points
> simultaneously, each sensing circuit feeding a BNC connector. Current
> sensing done with hall effect current loops feeding op amp circuitry.
> Variac voltage and current displayed on panel meters.
Sounds like a nice setup with good capability once you get it dialled
in. You might have trouble with that SCR motor controller due to RF
hash on the mains. This goes for any solid state devices you might
put in your power cabinet. Hall Effect sensors are something I've not
experimented with so I cannot comment there.
You didn't mention how big guage the secondary was wound with, but if
it is #18 or larger you should be fine.
The toroidal topload sounds small. Go ahead and run with it though
since this is what you now have.
Keep us all posted on your results!