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- To: tesla@xxxxxxxxxx
- Subject: Re: Ballast?
- From: "Tesla list" <tesla@xxxxxxxxxx>
- Date: Mon, 04 Apr 2005 22:00:52 -0600
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Original poster: BunnyKiller <bunikllr@xxxxxxx>
ballasting is a process in which we use an inductor to "reduce" the
available amperage to a transformer. There are 2 basic manners to "ballast"
( reduce current thru a transformer) 1, use shunts in the output
transformer ( NST's OBIT's etc have them) or 2 , use an inductor in series
with the transformer ( pole pigs etc) to reduce the amperage to the trannie.
lets get back to basics... an inductor limits current via the change in
sine waves thru the coil wrapped around the iron core. As the current
"excites the iron core" it imparts in the core a magnectic flux, when the
AC sine wave changes direction, the magnetic flux in the core is still
traveling in the direction it was set origininally into. when the AC sine
wave changes direction, it has to fight the existing flux flow in the iron
core, thus reducing its effective capacity... thus a less total effective
On the other side... ( NSTs OBITs) Shunts are used to allow the magnetic
flux to "bypass" the secondary coil instead of sending all of the current
thu the transformer core( basically a shunt has less resistance than the
flow of flux thru the secondary coil and less resisttance means less flow
) and thru the secondary.... so in effect..it by passes the secondary
windings and resends the flux into a "void" as heat..
Pole Pig trannies have no shunts ( due to the "backwards design we are
using them as") but NSTs are designed to take a full short circuit load
without killing themselves ( but they WILL die from overvoltage of matched
LC combinations... resonate rise) leaving this up to you to learn
... learning is kewl...
Pole pigs are designed to "deliver" from the supplied voltage ( normally
7.2KV to 14.4KV ) into several A output ( think about it ... 1 pole pig
will cover 4 houses on average which can pull up to 100A at 240VAC
each ((24KVA)) so a 25 KVA pole pig will do the job ( but looking at
the pig on the pole outside my house which is rated for 15KVA (( big 15
painted on it)) supplies 4 homes) they are expecting less than the
demand.. when you hook up a piggie "backwards" it will be able to draw
what the piggie on the pole can deliver and brown out the homes on that
circuit IF YOUR WIRING is capable of pulling that kind of power ( most
homes dont have that capability)
fuses will blow and wires will melt first... not a pretty site...
use a ballast...
next.. how to design a ballast... complex to a degree... you need an
iron core of sufficient mass ( enuf center core to avoid saturation) ...
you need enuf wraps of wire to keep the "volts per turn to about 1-2 volts
( if you want to use 240VAC you need at least 200 turns to keep volts per
turn around 1-1.5 volts per turn per wrap"... you will need enuf wire
diameter to handle the amount of amperage that needs to flow thru the
wraps... a # 6 will handle 60 A 3 #10's will handle the
same...) 18-25 square inches of center core area will handle the
"saturation" point of the magnetic flux produced by the current.
What is magnetic flux saturation? when the current flows thru a core area,
it can only produce only so much flow before saturation takes effect
... if it produces more than the core can handle, it doesnt matter
anymore. Basically it over rides the core and can send more current thru
the core and over-power the effects of the core and you now have a
saturation effect... it no longer works as an inductor... but more as a
semi non limiting resistor to a certian point... the inductor will handle
up to a certian point of current limiting and if pushed beyound that point
becomes useless... it allows more current to flow thru it and is no longer
"suppressed" by the inductor and magnetic flow....
imagine a pressure regulator that can handle from 0 to 100 psi... after 100
psi input the regulator no longer fuctions and will allow the full pressure
to flow thru thus blowing up the air hoses.... OOOPS
scary isnt it ...
so in retrospect... a ballast limits current to the load ( the
transformer) which allows one to limit the current to a non ballasted trannie..
ballast can be used to limit current flow to anything basically....
all depends on how you design it ....
if you want more info on ballast design email me at bunikllr@xxxxxxx
Tesla list wrote:
Original poster: "Steven Steele" <sbsteele@xxxxxxxxxxxxx>
What exactly is a ballast and what's ballasting?