View Single Post
  #52   Report Post  
Posted to rec.crafts.metalworking
Winston Winston is offline
external usenet poster
 
Posts: 3,444
Default Hot wire cutter question, power supply

Joseph Gwinn wrote:
In ,
wrote:


(...)

That all looks inductively reactive to me.


Then there is problem with the spice model. More below.


Joe, I did the experiment in the real world just now.

You are right. With a resistive load on the secondary
I saw undetectable phase shift between voltage and
current on the primary. With an inductively reactive
load on the secondary, I saw the expected significant
lag in the current peak in relation to the voltage peak
on the primary.

That will be what I learned today and I thank you.

(...)

War story: Many years ago, I was interested in the physics of xenon
flash lamps. The physical model is pretty simple, a charged capacitor
discharging into an arc, which arc heated the xenon to incandescence,
the resulting light and heat radiation carrying the energy away. This
yields a set of coupled ordinary differential equations that one solves
numerically, time step by time step. I got it all working, and all was
well. Then I changed the duration of the time steps, and more energy
came out as light and heat than was stored in the capacitor. Oops.
Violated the conservation of energy.

Turns out I had made two mathematical mistakes, which mistakes cancelled
one another only for the original step duration.


Wow!
That one must have had you scratching your head for a while!

Thanks again

--Winston