Re: What kind of PFC Capacitors

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Dan,

There are two kinds of motor caps.  "motor RUN" and "motor START".  You
need to get the motor "RUN" types that are made to run continuouosly.
Motor start caps will overheat and explode in about a minute.  Motor run
caps are larger and lower value than the start types.  The run caps change
the phase to the motor windings as it is running where the start types are
for very high current but very short time starting duty.  The run types are
usually oil filled poly for handling current contuously.  Note that motor
run caps are very expensive new, but dirt cheap surplus.

Cpfc = ( Vo x Io ) / ( 2 x pi x f x Vi^2 ) 

Where 
Cpfc = Power factor cap value in Farads 
Vo = Rated NST output voltage in volts 
Io = Rated NST output current in amps 
pi = 3.14159... 
f = AC line frequency (50 or 60Hz) 
Vi = AC input voltage (120 VAC) 

The exact value is not important here.  It is best not to go too much
higher.  Lower is better if you have a choice.  Some more precise values
for static gap systems are given in the tables at:

http://hot-streamer-dot-com/TeslaCoils/Misc/NSTStudy/NSTStudy.htm

But unlike primary cap values, you can be way off with little harm.

Cheers,

	Terry




At 08:29 AM 7/13/2002 -0400, you wrote:
>
>
>	I would like to add some PFC Caps to the input of my NST.  What kind
>of caps are typically used for this and how do i determine the value?  Are
>these just standard motor type capacitors?
>
>	Thanks
>	Dan
>