Re: Saturable Reactors

NeonGlow-at-webtv-dot-net (Tony Greer) wrote:

>Hi Bill, Marco, Scott, & coilers all!                             
>This "little-known-today" device known as a saturable reactor is 
>still being used today in controlling neon tube bombarding 
>transformers in the 7.5 kva to 15 kva range. It is simply placed in 

Great.  I'm glad to hear of one modern use for this thing (saturable 
reactor).  I'm told that Harmon Cardon(s?) audio amps also/used to use 
this technology...

Dang - a 15kva bombardier?  What size tube is that one for? :)

>series with one side of the primary, It is the most desirable (and 
>expensive) method of doing so. The output from a small Variac is 
>full-wave rectified and feed into coils of the reactor affecting the 
>magnetic saturation of the core, and thus the reactance. Reactance is 
>decreased as Variac voltage is increased. Price for a 15 kva reactor 

So this reactor has two coils - one is the DC control coil, and one is 
in series with the pig???

>is about $1400. Normally, bombarders have a (almost) purely resistive 
>load of the neon tubes being processed, and the control of my 15 kva 
>/ 24 kv bombarder is smoothley controlled from about 75 ma to over 1 
>amp in the secondary. HOWEVER, Bill's post got me to wondering how 

Well, yea, but the neon sign's V/I curve has a negative slope.  
Something in there is required for stability.  I woonder if this is a 
side-effect of the saturable ballast too??

(ie - if you just run a neon tube across an unballasted pig - it'll draw 
more or less infinite current!)

>the reactor would react to a capacitive load, so I placed a .08 
>-at-100kv commercial capacitor in series with the neon tube I was 

Hmmm.  An excellent experiment.  My books don't describe what happens 
with capacitive loads!

>bombarding. ALL CONTROL WAS LOST with the cap. in circuit ! I know 
>this is far from what a Tesla tank circuit represents, but the 
>reactor was clearly not happy with capacitance in the circuit. As 

I wonder what would have happened with a cap in series with a 
traditional resistive (ie - not a neon tube) load??

>soon as the Variac was raised from 0 volts, current in the secondary 
>rose uncontrollably to near maximum within a second or two, and could 

Hmm.  Strange that it took that long to max out!  Wonder what was 
happening??  What eventually limited the current?

>not be lowered (untill power was removed). Saturable reactors WOULD 
>be a GREAT way to control a pig if it wern't for the price (unless 
>you could build one) and any adverse reactions from the T.C. tank 
>circuit. Sorry, but this is about all I know so far, just thought I'd 
>let you know of my experience with mine. Merry Coiling to all !!!    

Well I really appreciate hearing the results of that test.  If possible, 
could you try it with a cap and a resistive load??

Thanks Tony!

-Bill the arcstarter
Starting arcs in Cinci, OH

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