Re: Ballast training 101

["Jim Lux" <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

>>
>Yes. Do you have a meter that can measure inductance? If so, you are ahead
>of the game. You can calculate the required reactance in Ohms to limit the
>current in your transformer to the desired level by using ohms law. (you
>don't need to worry about phase angle, power factor, etc. just pretend the
>circuit is linear and you are using a resistor, all you want is a number, a
>magnitude, not a vector.) Then find the inductance from the inductive
>reactance at the desired frequency, and find a sol. that is close to that
>value with the plunger removed.


leaving things like saturation aside, you could empirically measure all this
by putting a resistive load to stand in for your pig (i.e. something like a
1 ohm resistor, maybe 0.5 ohms might be better... what you want is the DC
resistance of your pig)  in series with your inductor, exciting with a low
voltage (say 12VAC from a filament transformer or such like) and measure the
current and voltage on the load.  Then scale appropriately...

For that matter, you could just run the pig and ballast together at 1 volt
in...




That should get you in the ballpark.
>Just be sure that whatever you use as ballast, should it be a sol. or a
>transformer, or even a light bulb, is designed for the full voltage you
will
>be putting into the circuit. When I was doing the "ballast training 101"
>thing on my own, I found a transformer that had the "ideal" inductance to
>limit my pig to the same output as a 15/60 NST. It was from a battery
>charger for a golf cart. The problem was, it was designed for 120V and when
>I put it in series with the low voltage windings of the pig, it would go
>into saturation just about as the limiting effect started to kick in, with
>some rather interesting effects.
>
>> Again, yes, this seems a bit silly, but it's a *LOT* less dangerous than
>> MOT's, and if it does bite me, I 'll only get a nasty,
>> substantial jolt and
>> live to coil on.  The goal is *not* to get bitten, however.
>>
>Actually it does not seem silly at all. It does seem safe. And as always,
>much better safe than sorry.
>
>later
>deano
>
>>  Ideas?  Comments?  Think it'll even work?
>>
>>   Sundog
>>
>>
>>
>
>
>
>