Voltage regulation wrt resistive and inductive loads...

Page 2 of 3  


> I haven't yet tested it with purely resistive loads, cuz, well,
PURELY resistive? Where in the heck would you find a PURELY RESISTIVE load?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

>PURELY resistive? Where in the heck would you find a PURELY RESISTIVE

Oh, Attenuators. I didn't know that. I guess that part of the circuit is purely resistive or resistive/inductive.
(I just looked up "purely resistive")
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

An electric heating element, like a range element, toaster, heater without a fan, water heater, light bulb etc are examples. They all have some theoretical small inductance, capacitance, too, but it's so tiny it can be ignored. The voltage and current through those devices is in phase.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:> Awl --

An electric heating element, like a range element, toaster, heater without a fan, water heater, light bulb etc are examples. They all have some theoretical small inductance, capacitance, too, but it's so tiny it can be ignored. The voltage and current through those devices is in phase. =================================================== Turns out I have a not-so-bad testing solution. Altho an electric range top would be great, I have a bunch of 240 V electric baseboard heaters, 10 A at 240 V. So just five of them will give me a 50 A load at 240 V, about what the unit is rated at, and I will be able to plot V vs. I, ito regulation. I also have a bunch of regular 120 V space heaters, but the 240 V stuff makes wiring easier. Won't get to this 'til about Wed/Thurs, tho. Still have to deliver my CO report.... now that I've recovered..... LOL
--
EA





Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ill repeat my reply here for the sake of those that filter google groups
thats actually a real interesting question...
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'm sort of guessing that myself, but I hope it's not so. With out-of-phase voltage current, I'm ALREADY worse than 12% regulation, and if this hunch is correct, pure resistive would make it even worser!
We'll see what happens. I'm amp-probing the current, metering the voltage, so I can repeat the welder load, do the pure resistive load, and compare both V vs. I plots.
Hold yer brefs until Thurs/Fri.... LOL
--
EA


>
>
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You neglect the resistance of the generator windings.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I don't see that he neglected the resistance of the generator windings. In a generator the resistance of the windings is very small, negligible compared to the resistance of any real load.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

If there is no resistance in the load (ie purely inductive/ capacitive), it would be the only resistance in the circuit and hence hugely important.
There is no such thing as a pure inductor BTW. There are almost pure capacitors.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Uh, huh. So, why did you just bring such a load into the discussion?

Uh, no. The generator winding resistance is still small. Small is still small, whether you have a purely resistance load or a load that has a substantial component of inductance or capcitance, like the welder in question or a motor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Someone else did.

Uh............Yes. The resistance however small will be the only thing in the circuit consuming any energy.
One considers the Inductive element of a circuit separately when doing any calculations.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

And there you have it folks, after telling others here that they have s*** for brains, the village idiot has once again demonstrated that he's the one that is clueless.
Resistance is most certainly *not* the only place energy is consumed. Take a simple electric motor, for example., like the one powering a water pump. If resistance is the only place that consumes energy, how do you account for the work done by the motor? The motor isn't a resistance heater and the energy is being used pushing the water. According to your logic, if we had a 1hp motor, all the power would have to be in the form of resistance and we'd actually have a 750watt heater.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

We were discussing the electrical losses in a generator. And the heating losses in the generator arise from the resistance of the windings (copper losses) and the magnetic hysterisis losses of the iron core. If there was no resistance. there would be no copper losses.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Nice try at back peddling. We weren't discussing the resistance of anything. Mark made a post about the voltage regulating characteristics of the generator. Then you claimed that the resistance of the generator matters. The guy is hooking up a frigging welder. THAT is significant in regard to voltage regulation. The very small resistance of the generator is not.
Then you went even further off the rails:
"Uh............Yes. The resistance however small will be the only thing in the circuit consuming any energy. One considers the Inductive element of a circuit separately when doing any calculations. "
Clearly a circuit, is, well a circuit. It's *not* just the generator windings. It's the generator plus the load. Your statement means that there is no other energy transfer in a circuit with that welder or a motor, other than through resistance. THAT is just wrong.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

> They all have some theoretical small inductance, capacitance, >too, but it's so tiny it can be ignored. The voltage and current

I mean, you know. To be technical, in DC/AC/Grounding in electrician school, they teach you that nothing is "purely resistive"
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

True. But electric heaters are near as dammit for practical purposes.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 13 Jan 2013 12:40:11 -0800 (PST), Transition Zone

A heater?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
A large block of carbon crystal with plates on the outside. Compression of the plates changes the resistance.
Used them in lab experiments. 200 amp switcher supplies.
Martin
On 1/13/2013 2:40 PM, Transition Zone wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

You can buy one. Sewing machine speed foot control.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Used to be used for speed control in electric trolleys, circa 1910.
<http://books.google.com/books?id=9zMPAAAAYAAJ&pg=PA29&lpg=PA29&dq rbon +pile+rheostat&source=bl&ots=G0OU5QxYJv&sig=hMmbFwem2ne9HADMpw6RunAhqOg&h l=en&sa=X&ei+X0ULi9KJKD0QHX_IGgCA&sqi=2&ved EQQ6AEwBA#v=onepage&qr bon%20pile%20rheostat&flse>
Joe Gwinn

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.