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Re: Ok.. where am I going wrong

 Bart:

I think you missed something here. If he measures the voltage drop across
the resistor (17V), then by E/R=I the current through the resistor and
therefore the rest of the series circuit is 42.5 Amps; regardless of the
resistance/impedance of the other circuit components. If the .4 ohm
resistor were the only thing in the circuit it would draw 240/.4=600 Amps
and the fuse would indeed blow! 

Michael:

Depending on the exact type of fuse, it may well hold on a 140% overload
for some time (minutes to hours). There are several types of 'fast-blow'
fuses and the only way to be sure is to look at the time/current curves for
the particular one you're using. Also, how precise is your resistor value
and how accurate is your volt meter? 

- Mike

> Michael,
> For current flow, you must have both sides of the AC joined together. The
> current flows back and forth from one leg to the other through the
> components in
> your circuit. The components are all in series forming a circuit "loop".
The
> 0.4ohm resistor is just one component in the loop. In order to
"calculate"
> current flow in the total loop, you must account for all resistance
including
> the resistance and reactance of the ballast, pig, etc... If your 0.4 ohm
> resistor was the only thing in the circuit, then you would draw 40+ amps
> across
> the resistor and blow your fuses. Obviously, the current is being limited
> by the
> other components in the circuit.
> 
> Hope this helps,
> Bart
> 
> Tesla List wrote:
> 
> > Original Poster: "Coiler" <mycroft-at-access1-dot-net>
> >
> > I just finished wiring up my pig-training facility. This means the
> > welder, 0.4 ohm resistor and 240V feed. I had thought to calibrate the
> > switch settings on the welder to KVA numbers by taking voltage readings
> > across the resistor. The infamous V=IR business. Only.. it didn't work.
> > Or I don't think it did. At one point, I measured a drop of 17V. This
works
> > out to roughly 42 amps. This cannot be. I have 30A fast blow fuses in
the
> > line
> > and I suspect that they would fry in short order at almost 50%
overload.
> > Therefor, there must be someting I am missing. I assume it is related
to the
> > fact that this is AC.
> > Could someone help me out here? Tell me where I goofed.
> >
> > Michael Baumann
> > Coiler, Homebrewer, Nerd. mycroft-at-access1-dot-net