| Click to Post a New Message!
Page | | | | | | [ 7 ] |
| | |
|
3 Pt PTO generators
Mark;
I don't know what generators you have been looking at but to obtain an alternating current of proper frequency you need to have the alternator/dynamo spinning at a proper rpm.
I guess if you have a DC generator and AC coverter you could work the system increasing the speed as you draw current, but this would only add complexity and lower reliability. The only generators I have seen like this are for welding.
Peters
|
|
 Add Photo
Bookmarks: |
|
| |
|
3 Pt PTO generators
Well, let's try another illustration. Somebody is working with a backhoe, and the hand throttle is set for a desired rpm. The engine load goes all the way from the hoe not moving to digging forces that open a pressure relief valve.
If the engine stays at the same rpm, I'm curious where the power comes for the high loads except through increased fuel delivery. As far as I know for a given engine and rpm more load equals more fuel delivery equals increased throttle. I know that on my hoe, the rpm stays constant when I dig. It's not me that's changing the throttle, but I believe I can sure hear it change when I dig.
I believe I wrote a reasonably good description of how a typical mechanical governor on a tractor engine works. There are other types, but I haven't heard of any that don't vary the throttle under changing loads to keep constant rpm.
Anyway always a chance to learn something new and if there's another explanation then I'd surely like to hear it. However, I'm so sure of the basic idea that if I dug around for some tables I probably could come up with a rough estimate of how much extra fuel a 1KW generator load would require. There's probably a way to get from fuel to BTU's to HP to watts. I already did the watts to HP part.
HP is not just an engine spec, it's a measure of work done (550 ft lbs/second). An engine doesn't do work unless its delivering HP and the amount of HP delivered depends on the load and speed rather than the engine. There is a link between HP (or work done) and fuel. An engine is a way of producing btu's from fuel. BTU's equals energy equals work done. More work equals more energy equals more fuel. The throttle just has to change to keep the same load moving at the same speed, and the governor is what does it as far as I know.
|
|
Add Photo
Bookmarks: |
|
| |
|
3 Pt PTO generators
In the above post I tried to reduce the idea to its basics. If I'm right I hope the post helps sharpen up ideas about how things work. If they're wrong, I sure want to know about it.
My standalone generator does have an automatic no-load throttle that drops the rpm in absence of a load. The voltage meter on the generator does decrease about 20V when the rpm drops. I've thought about why and don't have a ready explanation. Alternators change the output voltage by varying the field current to change density of the magnetic field. I don't know if generators do the same. I do know that output voltage is expressed as RMS voltage. RMS is .707 of the peak voltage for a true sine wave and doesn't change with frequency. Most generators don't produce a true sine wavy and a meter calibrated for RMS voltage may not be accurate if the wave form changes at lower RPMs. Just some ideas here and maybe I'll get my ideas about how generators work sharpened up.
|
|
Add Photo
Bookmarks: |
|
| |
|
Page | | | | | | [ 7 ] | Thread 1372 Filter by Poster:
3 | 1 | 2 | 2 | 1 | 1 | 1 | 3 | 1 | 1 | 1 | 3 | 2 | 1 | 2 | 1 | 1 | 2 | 3 | 1 | 5 | 1 | 1 | 1 | 3 | 1 | 1 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 1 | 1 | 6 |
|
()
Picture of the Day
DennisCTB
Unanswered Questions
Active Subjects
Hot Topics
Featured Suppliers
|
Gas Generator Weather Protecti
12-26-2002, 18:14 
Pics
Reply
Digg It 
Del.icio.us