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Re: [TCML] A few questions, any help would be great
Hi Brian,
The resistor size calculation is fairly simple. 15000v/20 resistors=750V
rms across each resistor. W=E*E/R W = 562500/R. Thus a 5 Meg resistor will
dissipate a little over 1/10 watt, so power is not a problem. Usually,
physically larger resistors are used because their length prevents arc-over
along the body of the resistor. Many people use two in series to increase this
length. The other consideration is how fast you want the voltage bled off
the caps. The time constant is T(sec)= RC where R is in ohms and C is in
Farads (or equally, Megohms and microfarads). 10 Meg would give you about 2.2
sec. 5 to 10 Meg per cap is what the majority of people that use them are
comfortable with.
The strike rail, the center of the safety gap, and the secondary should
be grounded to the HV ground.
The primary sees the NST voltage, so the gap size in the strike rail is not
critical as long as it is larger than you will ever set your safety gap.
There is no ideal height for the strike rail, as long as an arc coming off
the toroid "sees" it before it "sees" the primary. I just use equal to
outer diameter and a couple of inches above the plane of the primary.
You can read the archives for more detailed explanations, but do not be put
off by the few perpetual sophomores who like to DIS the freshman, and feel
the need to fill up bandwidth to explain why they will not answer your
question. ;^)
Matt D.
sparkin' since the 50's and still alive.
In a message dated 9/29/2009 10:05:41 P.M. Eastern Daylight Time,
quarkster@xxxxxxx writes:
All these questions have been asked, and answered in detail, many many
times
before on this list.
All the posts to the TCML for the last 16 years are archived on the TCML
website at www.pupman.com. You can easily search these archives for
answers
on almost any Tesla coil topic you can imagine (the "Search the Archives"
link is on the left-hand margin of the home page).
If, after searching the archives and reviewing the information therein,
you
cannot find the answers to your questions, then feel free to post the
question to the list.
By doing a little research FIRST, you will find the answers to 99% of your
questions, and be able to see the responses, experiences and opinions of a
number of list members.
Regards,
Herr Zapp
----- Original Message -----
From: "Brian Hall" <brianh4242@xxxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, September 29, 2009 5:07 PM
Subject: [TCML] A few questions, any help would be great
Hi,
I sent these a week or so back and never got any replies, maybe the
message
didn't go through. I have done lots of research and recieved much
guidance
in building my TC, these items that folow are some of the gaps that I
would
like to fill in, to get the best, and safest, performance out of it.
Even if you know an answer to just one of the questions, or can help point
me in the right direction, any help would be appreciated.
###########
How does one calculate a good bleed resistor Ohm and Wattage rating for
each
cap in an MMC?
Let's say for example, connected to the 15/30 NST, I have 20 caps, each
one
2000 volts and .22 uf, all in series (for 40kv @ .011 uf total)
Is there some kind of equation that I can plug those numbers into, to get
the right value for the bleed resistor between the leads of each cap in
the
MMC? Does SG size get involved?
Also, for items that need to be RF grounded to a metal pole in the dirt
-case of a 15/30 NST
-secondary coil
-backflow protection for the NST, gaps to over-arc to a ground point
instead
of blowing out an NST leg (I think it's called a Terry filter?)
Should I also ground the strike rail? (also is there an equation for how
wide the gap in the strike rail end points should be, and how high above
/what radius gap should be, between the outermost turn of a flat spiral
primary and the strike rail?)
And can all the above be grounded to the same earth point? Or should
separate ground points be used on .. which items?
----------------------------------
Brian Hall
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