Re: Capacitor calculations
Subject: Re: Capacitor calculations
From: "SROYS" <SROYS-at-radiology.ab.umd.edu>
Date: Tue, 26 Sep 1995 10:41:16 EDT
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> I have seen several postings recently regarding calculating the
> correct capacitor size for a given transformer. I assume these values
> are coming from a program such as TESLADP. I tried this for my pole
> pig and get a value of .064 mfd. What does this mean? I would
> guess that this is the maximum value this power supply can charge
> effectively in a tesla tank circuit?
I'm not familiar with the Tesla programs either , but I have seen
capacitor selection described as a problem in impedence matching (i.e.
- for the most energy transfered, the impedence of the load should
match the impedence of the source).
In English, for a transformer with a given voltage (=V) and current (=I)
rating, you first calculate the impedence that will load the transformer to
it's rated capacity (R=V/I). For the maximum output from a transformer,
the capacitor you choose should have a capacitive reactance (=Xc)
equal to the transformer's impedence (=R) at your line frequency (f =
60Hz here in the good old USA, 50Hz elsewhere). The capacitive
reactance can be found using Xc = 1/(2 * pi * f * C) where C =
capacitance in Farads. From the desired Xc that you computed, it's
simple to find C = 1/(2*pi*f*Xc) to fully load your transformer. Since this
formula is for the steady state condition and a capacitive discharge
Tesla coil is not running at steady-state, the value of the capacitor
found above can be increased by 50% to 100%.
Steven Roys (sroys-at-radiology.ab.umd.edu)