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Re: New Coiler


From: 	Mark S Graalman[SMTP:wb8jkr-at-juno-dot-com]
Sent: 	Wednesday, September 10, 1997 11:57 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: New Coiler

    Patrick, I forgot to mention that a single static gap at this power
level simply will not perform. 
I would suggest using 8-10 series gaps at about .025" each placed in a
strong air flow from a couple
of good muffin fans

                                                                    Mark
Graalman


On Wed, 10 Sep 1997 09:51:32 -0500 Tesla List <tesla-at-pupman-dot-com> writes:
>
>From: 	Mark S Graalman[SMTP:wb8jkr-at-juno-dot-com]
>Sent: 	Wednesday, September 10, 1997 7:28 AM
>To: 	tesla-at-pupman-dot-com
>Subject: 	Re: New Coiler
>
>
>
>          Hi Patrick,
>
>   Here's my 2 cents worth:
>
>On Tue, 9 Sep 1997 22:22:57 -0500 Tesla List <tesla-at-pupman-dot-com> 
>writes:
>>
>>From: 	Patrick J. Gustafson[SMTP:gustafpj-at-uwec.edu]
>>Sent: 	Tuesday, September 09, 1997 4:12 AM
>>To: 	Tesla List
>>Subject: 	New Coiler
>>
>>Hello all, 
>>
>>I have been patiently reading the list for quite some time now, but I
>>could not get my questions to post on the list.   Thanks to Chip, 
>this
>>problem has been finally resolved. Here are the concerns that I have 
>>as
>>of yet:
>>
>>
>>1.   I have a two layer secondary coil with 28 gauge wire close wound
>>for 21.6" (both layers).   The first layer is at 6" in dia. and the
>>second layer is at 6.125" in dia.   The calculated resonant freq's 
>are
>>108.71 kHz and 106.45 kHz respectively, and the calculated 
>inductances
>>are 91.84 mH and 95.49 mH also respectively.   Now since I layered in
>>parallel, can I add together the inductance values directly? ( i.e. 
>>the
>>new value would be 187.33 mH)   
>
>    No, when inductances are placed in parallel the total value goes 
>down
>and will be less than
>the least value of inductance, in this case the total inductance would 
>be
>about 46.8 mH
>  
>   Thats alot of inductance for a 21" tall coil, The concern I have at
>this point is I feel for the amount
>of power your going to run into this coil the height of the coil maybe
>too short.
>
>>2.   Should I be concerned with the differing resonant freq's when
>>calculating the needed primary capacitance?
>
>
>   No, the two frequencies are close enough, you could just call it 
>107
>khz. But, in reality this 
>frequency means little because the actual secondary frequency will go
>down with the addition of
>a top load such as a sphere or a torus and then drop maybe another 
>10-15
>khz while under sparking
>conditions.
>
>>3.   How do you determine  (a) the inductance (of chokes) needed to 
>>stop
>>the voltage spikes from reaching the NST's, and  (b) what ratings the
>>parallel resistors that accompany these chokes should have?
>
>  Here IMHO there is no need to calculate, I would shoot for about 50 
>-
>100 uH in a air wound
>choke and a few mH in a ferrite core choke. The De-Qing resistors are 
>not
>placed in parallel with
>the chokes but are placed in series with them and for a NST I would 
>use a
>1 K ohm 25 watt wirewound.
>
>
>>4.   What capacitance should I use for my protection cap. given the
>>power supply below?
>
>      Two old TV style doorknobs (500 pf 20 kv) in series from each HV
>terminal to the transformer
>case work well. This value really isn't critical, I'd just try to stay
>between 100-250 pf and keep the
>leads short. What you really DON'T WANT is to have a resonate point in
>your filter (choke) system
>anywhere near the actual operating frequency of you coil.
>
>>5.   For the protective spark gap for the NST's, how is the ground
>>electrode incorporated into this?      
>
>       The ground electrode is the center electrode and it is tied to 
>the
>transformer case which is tied to
>   earth ground.
>
>>Here are the specs. of my Tesla coil:
>>
>>Primary Coil - 16 turn, 1/4" soft copper tubing with 5/16" spacing.  
>>Inner dia. is 8" and outer dia. is approximately 25".
>>
>>Secondary Coils - As stated above.   Note: Went for inductance by 
>>using
>>28 gauge wire, also to see if it can withstand the punishment.
>>
>>Power Supply - 15 kV -at- 90 mA NST's.   ((3) 15 kV -at- 30 mA in parallel)
>>
>>Toroid - 25" outer dia. with a 5" cross section.
>>
>>Spark Gap Electrodes - 3/4" thick by 2" long highly polished steel, 
>>with
>>3/8" radius of   curvature on one end.
>>
>>Spark Gap - Single static.
>>
>>Components not made yet:
>>
>> - Primary capacitor (Calculated to need about .0226 uF.   Anyone 
>have
>>problems with using mylar for the di-electric?)
>> - Protective capacitor.
>> - Chokes.
>
>   Under no circumstances use mylar for a pulse cap, it will melt at
>best! Mylar cannot tolerate HV AC
>voltages and peak currents. 
>
>>
>>Some info:
>>
>>I am a Physic's major, mathematics minor at the University of 
>>Wisconsin
>>Eau Claire, so I am quite familiar with most of the terminology 
>>involved
>>in Tesla coils.   This is my first Tesla coil project, which I am
>>building for the Physic's Dept. (and they are funding!!) for
>>demonstrations on inductance and E&M fields.   I can already see the
>>limitations of these 2 coil systems, and may soon have to start
>>researching into magnifiers.
>>
>>Any help greatly appreciated.
>>Patrick Gustafson
>
>                           Mark Graalman
>
>
>                                                                 
>
>
>
>