Re: Ballast Resistance For Pig Coils (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Sat, 27 Oct 2007 13:37:42 +0000
From: David Rieben <drieben@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Cc: drieben@xxxxxxxxxxx
Subject: Re: Ballast Resistance For Pig Coils (fwd)

Hi Adam,

I have used resistive ballasting in series with my inductive ballast
in my control panel for my big coil before. As far as the "thump-
ing", I have experienced it, but only on a few occasions. I think 
the thumping is a result of the inductor resonating with the trans-
former so that would probably explain why it goes away when 
you change the BPS rate. I was using huge power resistors for
about 1 ohm of additional resistance to the ballasting circuit. 
However, I do not like the resistance approach as large amounts
of power are wasted in the form of heat. I had to run forced
air across the resistors and they would still glow cherry red! It
made for a nice incidental shop heater during the coldest winter 
days, but wasn't worth a crap the rest of the year, especially du-
ring that long string of 100 degree + days that most of the south-
ern US experienced this past August. Actually, I rarely get to 
fire my big Green Monster coil since I have to roll it out on the
driveway and fire it outdoors in front of suburban neighbors but
I do use the control panel pretty often to fire my monster Jacob's
ladder inside. I think many bigpig coilers manage to get around
the power-wasting (and voltage dropping) power resistors in 
their ballasting circuits these days. I would try either going back
to the welder ballast or adjusting my breakrate to stop the 
thumping before I'd break down and use resistors. However,
if you're determnined to go the resistor route, I still have the
big resistors that I was using in my control panel that I would be 
willing to sell since I have no intentions of going back to resis-
tance ballasting at pole pig power levels. ;^)

--
David Rieben

-------------- Original message -------------- 
From: "Tesla list" <tesla@xxxxxxxxxx> 

> 
> ---------- Forwarded message ---------- 
> Date: Fri, 26 Oct 2007 17:41:37 -0700 (PDT) 
> From: Yurtle Turtle 
> To: tesla@xxxxxxxxxx 
> Subject: Ballast Resistance For Pig Coils 
> 
> What size resistance are you folks using inline with 
> ytour ballast for their pig powered coils to prevent 
> "thumping"? I decided to tune up my coil this evening 
> in preparation for Halloween. I recently started using 
> two slide inductors instead of my welder. This evening 
> all was running well, as I slowly cranked up the amps. 
> As I got to around 25 amps, the actuator motor died on 
> my Powerstat stack. I replaced the fuse, and it blew 
> again. I decided to set the voltage, then remove the 
> fuse, to keep from risking damage to the stepper 
> controller board. As I continued to run, I heard 
> several hard thumps from my powerstats. I quickly 
> turned up the breakrate, which solved the problem. 
> However, I noticed that the line in to the Powerstat 
> actuator had flashed over to the chasis. Apparently I 
> am getting some nasty spikes that I hadn't experienced 
> with the welder. 
> 
> I know folks have advocated using resistance in line 
> with their ballast. Is there a way to calculate what 
> resistance is effective at certain configurations, or 
> is it more trial and error? 
> 
> The reason I'm concerned is I don't want to blow up my 
> Powerstat actuator or my VFD. 
> 
> I have EMI filters between my incoming power and my 
> pig/ballast, but maybe I should consider something for 
> voltage spikes. While a spark gap for 120/240 sounds 
> silly, and hard to set, the 120 volt input to my 
> actuator jumped 1/8" to the grounded chasis. Without 
> having access to some kind of power monitor, I 
> wouldn't know if MOV's would last for years or 
> seconds. 
> 
> http://www.hot-streamer.com/adam/bigass_coil/schematic.pdf 
> 
> thanks 
> Adam 
> 
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