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Re: Large Transformer Question w/ Formula (fwd)





---------- Forwarded message ----------
Date: Sun, 15 Feb 1998 02:25:30 +1100 (EST)
From: Rodney Graham Davies <Rodney.Davies-at-anu.edu.au>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Large Transformer Question w/ Formula

Hi Guys,

On Fri, 13 Feb 1998, Tesla List wrote:

> Jeff and all,
> 
> Tank cap size is a function of the transformer's output voltage and the
> operating frequency. The higher the output voltage, the larger the
> current capability needed. A rule of thumb is about 0.01 uF for every 60
> mA off a 15 kV transformer. For example, the following table can be used
> for approximate sizing:
> 
>                     uF       uF 
>                   Max -at-     Max -at-
>      kV    mA     60 Hz     50 Hz
>      ==    ==     =====     ===== 
>       9    30     0.008     0.011        
>       9    60     0.018     0.021
>      12    30     0.007     0.008
>      12    60     0.013     0.016
>      15    30     0.005     0.006
>      15    60     0.011     0.013
> 
> The table can be scaled for larger current values as appropriate.
> 
> Hope this helps!

To make things easier on others who don't have a voltage & current 
setting on the above table, use this formula.

		  1
	C = --------------
	    2 * Pi * F * R

	Where, C - Farads
	       F - Mains Frequency in Hz (ie USA - 60Hz, Aust - 50Hz)
	       R - Impedance of transformer (V/I) Ohms
		   eg. NST rated 10,000V 30mA
			V = 10000 volts, I = 0.03 amps
			R = V / I = 333333.333 Ohms

This is an ideal formula for matching a capacitor with your transformer 
for resonant charging (maximum efficiency).

Catchya!
Rod