Indubitably wrote:So are you saying that the back emf sort of fills in the gaps between the pulses, and that this more or less makes the wave look smooth?
Sort of. As a magnetic field collapses in a coil, it induces current in the same direction that it was already flowing, so it keeps the current more contiguous. If the pulses are short enough and long enough delay between them, then it becomes more difficult to maintain flow between them, without much larger inductors.
So you can think of coils (inductors) as storing current. So these are wired in series with a circuit.
Capacitors do the same thing, but with an electric field instead of a magnetic one, so they store voltage. Thus they are wired in parallel with a circuit.
Both essentially do the same thing, of averaging the power flow they are connected to.
The reasoning being that the power stored in the magnetic field would carry with it a kind of EMF momentum which would smooth out the power, the same way that the mass of the fly wheel would smooth out the power transfered to it by the machine gun bullets.
That's a passable analogy I suppose. I don't pretend to truly understand how this stuff all works, just that I can visualize some of it happening from my early electronics classes and the explanations by the guy that started me into ham radio before that.
You can also visualize it as a river flowing from a dam, and you are opening and closing the floodgates of the dam, for either shorter or longer times. That's the PWM duty cycle. The frequency is exactly that--how long between the tiems you open the gates. The dam always has about the same pressure (voltage) behind it, so the pulses are always about the same "height", just that they are not always as long.
Since the riverbanks are either narrow and high or wide and low, the pulses may stay as big waves down the river for a good distance, or they may fan out into much more level ripples--this is the equivalent of inductance or capacitance.
As for the light dimmer, I'm not sure that I follow what you mean by "chopping" up the sine wave. How does this increase my frequency?
It doesn't. It only allows you to use PWM to control voltage (and ultimately, current, based on the resistance of your load). If you have to change the frequency, you'll need an active controller of some type to generate the sine signals at whatever desired frequency range you wish.
Keep in mind I don't know how TIGs work, haven't used one or had one apart either. It was just a suggestion someone else gave me regarding how I might start building one of my own. So the info you gave in your post I'm replying to is a lot more than I had tos tart wtih.
I'll see what I can find on the dimmer though, if its cheaper and easier, I suppose you might just as well go with that. Do you know if the dimmer will also provide the variable constant current limiting effect we need?
That's what PWM (in anything) can do, by varying the voltage across the resistance of your load. You just need a circuit added to it that senses how much current is flowing, and feeds that info back to a circuit that alters the duty cycle of the PWM to control that current. It's what ebike controllers do, and chargers, etc.