Voltage regulation wrt resistive and inductive loads...

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Awl --
In a portable generator.
Does one type of load vs the other make it more difficult for a typical portable generator to maintain constant voltage? Esp at a current approaching the continuous current limit of the generator.
I ask bec the mfr claims 1-2% regulation. A small miller welder is causing 12%+ variation, within the current limitations, with the voltage variation being fairly proportional to load. I'm assuming a transformer load is substantially inductive?
I haven't yet tested it with purely resistive loads, cuz, well, this would require a lot of heaters, a pita to wire up.
--
EA



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Existential Angst wrote:

In real world situation you will have hard time finding purely resistive load. Most loads are inductive affecting power factor. IMO, your generator maybe border line under powered for the welder.
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with a pure reactive (inductive or capacitive) load, the current flow in the windings will cause a voltage drop but if i'm not mistaken since there is no (or very little) actual power flow, there will not be a load on the engine so the engine speed will not be a factor.
with a pure resistive load, the current through the windings will cause a voltage drop AND there will be a load on the engine that will try to slow it down. It is the job of the speed governor on the engine to keep the speed constant. If the speed drops the voltage and frequency will drop due to the engine speed drop.
So for a given amps, you may get more of a drop with a resistive load depending on how tight the governor speed control the engine.
Mark
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On 1/12/2013 4:11 PM, Mark wrote:

If it's a transformer and a stick welder, is there reason to believe that the load voltage/current presented by the arc isn't relatively in phase? Would be interesting to see the V-I curve of a plasma under welding conditions.
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Tony Hwang wrote:

Just get an old electric range top. You can switch the loads on and off as necessary.
John
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Infinate burner controls don't present a steady load.
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PrecisionmachinisT wrote:

I did say old like in low, medium , high. or you could use a couple of electric baseboard heaters. John
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Or you could wire the elements up directly.
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All the generator cares is how much real power it takes to spin. It's not measuring LC, just measuring the final outcome. 1-2 % really surprises me.
Greg
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Not true. If power factor is bad, ( ie inductive) the generator can be overloaded at below it's rated capacity in Kw.
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wrote:

No, it cares about the current being supplied. Heating is done by the current, not the real power generated. Generators are rated in KVA, not watts.
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On Jan 13, 5:50pm, snipped-for-privacy@attt.bizz wrote:

Watts generated (in any conductor = Amps squared X resistance.
Poor power factor increases amps which means more heat has to be dissipated in the generator. (in the whole circuit in fact)
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On Mon, 14 Jan 2013 00:28:47 -0800 (PST), harry

What about "watts generated"? Is English your first language?

...and your point?
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On Jan 14, 2:01pm, snipped-for-privacy@attt.bizz wrote:

The point is that if power factor is poor, the generator will have to be derated you numbskull..
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On Mon, 14 Jan 2013 12:19:27 -0800 (PST), harry

Since you declined comment, I guess not.

That's already been said. Many times, moron.
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On Jan 14, 10:49pm, snipped-for-privacy@attt.bizz wrote:

Then why ask the question, shit fer brains?
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On Mon, 14 Jan 2013 23:16:00 -0800 (PST), harry

It wasn't a question, dumbshit. Really, is English not your first language?
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On Sat, 12 Jan 2013 17:10:58 -0500, Existential Angst wrote:

Depending on what's loading the transformer, a transformer load isn't necessarily substantially inductive.
That's the egghead theory. Unfortunately, my knowledge of welders starts with being able to stick weld, then has this long, dark, gap, then gets to the circuits theory that I know as an electrical engineer. So I couldn't tell you just what the power factor of a welder is (PF = how "resistive" it is). I can tell you that it probably varies with the type of welder, what its technology is, and probably by whether it's cheap Chinese or quality late-model 'merican.
--
Tim Wescott
Control system and signal processing consulting
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"Tim Wescott" wrote in message
On Sat, 12 Jan 2013 17:10:58 -0500, Existential Angst wrote:

Depending on what's loading the transformer, a transformer load isn't necessarily substantially inductive.
That's the egghead theory. Unfortunately, my knowledge of welders starts with being able to stick weld, then has this long, dark, gap, then gets to the circuits theory that I know as an electrical engineer. So I couldn't tell you just what the power factor of a welder is (PF = how "resistive" it is). I can tell you that it probably varies with the type of welder, what its technology is, and probably by whether it's cheap Chinese or quality late-model 'merican.
--
Tim Wescott
Control system and signal processing consulting
  Click to see the full signature.
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In purely technical terms,you generator should be rated on Kva not Kw.
If you have a resistive load, Kva and Kw are the same. A purely resistive load would be incandescent lights or electric heaters.
However, once you get into motor/transformers, the current and the voltage are no longer synchronised. (power factor) In practice it means that the load is drawing more current than you might think. So you can only connect a smaller load than you might think looking at the Kw rating. To know the load the generator will meet accurately you must know the Kva rating of everything. (ie both generator and load)
Welding transformers are particularly suspect, they have a "Poor power factor".
It's not a good idea to load a generator up to capacity anyway,especially in warm weather.
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