Re: Ballast bulk buy / Bombarder Chokes

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Neonglo-at-aol-dot-com>

In a message dated 8/9/01 9:47:17 AM Central Daylight Time, tesla-at-pupman-dot-com 
writes:

<< Hi All
 
 I have a lot of x-ray transformer laminations of various sizes. In
 particular I have enough laminations of size 22.75"L x 4"W to a form a bar
 core of size 22.75"L x 4"W x 4"H. I am thinking about making a bobbin that
 the core could slide through, and then wind the bobbin with very heavy wire.
 Does anyone think that this is a worthwhile approach to build a variable
 ballast? The big problems for me would be pulling heavy copper wire tightly
 around the bobbin, and constructing a mechanism for sliding the core. 
 
 Godfrey Loudner  >>

Hi Godfrey, All,

What you are describing here sounds like the way some neon bombarder chokes 
are made, which work really well on pole pigs too. They are basically what 
you describe, with a handle attached to the end of the laminations, and 
usually a mechanism to allow the core to be pulled out, but which will not 
let it be pulled back in. (This type of sliding choke is also a very strong 
solenoid!) 

While you can buy ready made chokes in sizes from 5 to 15 kVA, they are very 
pricey for what they are. They will cost in excess of $500, which is a lot 
for a laminated core and a coil of wire. (Here is a page from Daco Neon's 
catalog with a very fuzzy picture of a sliding choke and bombarder. 
http://www.daconeon-dot-com/page5.html ) I don't see why a very successful choke 
could not be made, especially if you already have the core material. Use a 
stranded THHN wire with enough capacity for the current you will be running, 
and build a very sturdy bobbin the length of the core. You will need some way 
of holding the core in position while it is energized, because it will have a 
very strong pull! Different length blocks of wood can be placed between the 
bobbin and a bracket on the end of the core.

I have both a 5 kVA and a 12.5 kVA sliding choke at the shop which I can get 
some of the important dimensions from if anyone is interested. If a suitable 
core can be found, the rest should be simple and straightforward to build. 

Tony  

------------------
Tony Greer
Special Effects Neon
Lubbock, Texas
"Flowing Glass and Glowing Gas"
       ~~~SINCE 1980~~~

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