Re: Ballast and wire stuff

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

Original poster: "Hydrogen18" <hydrogen18-at-bellsouth-dot-net> 

Since most tesla coil operation is fairly intermittent you can somewhat
ignore wire size unless it is doing a large percentage of the current
limiting(20% or more). It should be fairly trivial to buy a small bucket(3
gallon) and fill it with oil and put the spool in it I'd think.

For ballasting my 4 pack(which is similiar to a small pig)I went with 10 lbs
of 155 C 10 awg wire on a 3 inch form stuffed with welding rods. 15 amps at
240 volts.

---Eric
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, November 02, 2004 6:34 PM
Subject: Ballast and wire stuff


 > Original poster: Mddeming-at-aol-dot-com
 >
 > Hi All,
 >
 >      Well, I'm finally getting ready to retire my NST farm, the OBIT farm,
 > the MOT clusters, and plate-supply transformer, and start using my pole
pig
 > for something more than a doorstop/conversation piece. This brings up some
 > questions:
 >
 > 1) I know there is a rule-of-thumb that a couple of 500' spools of #10
wire
 > can be hooked onto the primary side as ballast and "all will be well".
 > However, I was wondering, " Is there a way to calculate the inductance
 > needed to limit the current draw to say, 30 Amps, even in the case of a
 > dead short on the secondary?"
 >
 > 2) What transformer parameters are needed to do the calcs beyond the 5
KVA,
 > -at-60 Hz. primary 240 V, secondary 14400 V?
 > 3) The off-the-shelf wire spools each measure 0.5 Ohm resistance and ~7.4
 > mH inductance.
 > and #10 wire is nominally NEC rated -at- 30 Amps. In a multi-layered ballast
 > coil, inside a cabinet, would these be subject to overheating? Will I need
 > a Hollywood-style wind machine and thermal relays in my control cabinet to
 > keep from smoking the system?
 >
 > 4) I vaguely remember a posting to this list from Fr. McGahee ca. 1998
that
 > said #10 bare copper wire could only handle ~24 Amps Max and about 21 Amps
 > steady load, and that was with plenty of free air space. Anybody remember
 > why the discrepancy?
 >
 > Thanks,
 > Matt D.
 >
 >


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