| |
|
|
Power stability with PTO generators
Obviously it wasn't built into every generator made because it wasn't built into my Gillette. And Gillette builds a LOT of generators.
|
|
 Add Photo
Bookmarks: |
|
|
|
|
Power stability with PTO generators
The critical thing about generators is speed. To get 60Hz power, most generators need to run at 3600 RPM which happens to be 60 revolutions per second. They produce one power cycle with a full rotation of the alternator. (This is not required by the physics of power generation, but by alternator design. Alternators could be made to operate at 1800 RPM and a nine pole generator could even be designed to work at 540 RPMs directly) Current producing capability of the generator is related only to its wiring size and steel content.
Having about 2 PTO HP per KW generated is a good factor to use. It provides some reserve and takes into account the efficiency loss of converting 540 PTO RPM to 3600 RPM at the generator shaft. Having three or four PTO HP available per KW generated will provide more stable power and high overload cabability at the expense of higher running costs at low loads.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Power stability with PTO generators
Ken, I stand corrected sir.
I surfed on over to the Gillette website and sure enough only some of the "GEN-PRO GASOLINE SERIES" generators are equipped with a "SPEED-MATIC controlled engine".
In fact I even looked Honda's own website since they are the principal supplier of engines for such things. They word it in an interesting way, they say some models are equipped with "auto throttle", not "idle control".
So I spoke to my dealer who sells the full line of Honda power products, all this talk of generators made me realize I have a little 1800 watt Honda unit in the garage that hasn't run in years, may as well take it in a get it running again.
He pointed out to me the source of my confusion. Almost every Honda, and most every other stationary type engine, has a vacuum type throttle, the engine automatically runs at a set RPM, if the load increases it feeds it a little more gas.
Mea Culpa.
Best of luck.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Power stability with PTO generators
Murf, thanks for the research and information. My inferior generator was causing me to feel very inadequate  Now I feel a lot better 
|
|
Add Photo
Bookmarks: |
|
|
|
|
Power stability with PTO generators
Wadda guy! (both of you!) We should all be so gracious.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Power stability with PTO generators
Art thanks for correcting. I did word the HP part poorly. You can have a larger generator than needed with only enough HP for your application...
Tom you are correct about the importance of the grid disconnect. The power people installed the Big lever disconnect to disconnect the complete service from the grid. But for what ever reason the shunts did not pull out. I'd have to go back and ask what happened and it was years ago...
|
|
Add Photo
Bookmarks: |
|
|
|
|
Power stability with PTO generators
Harvey: I'll bet the codes for transfer switches are different now. They got very particular about them 5 - 6 years ago around here.
A generator's main breakers are intended to protect it from overload and the breakers should work irrespective of tractor HP. But as Art said, they don't. I believe what is going on is that most generators have something less than a 100% duty cycle. They are capable of sustaining peak loads for limited periods and the breakers are sized to accommodate the peaks not the continuous rating of the generator. I think it's possible to burn up most any generator by carrying loads in the peak power range indefinitely and the mains won't pop.
I think most manuals sort of suggest this problem but they don't indicate the consequences very well nor say how to tell when loads in the peak rage occur. My Honda seems to cycle between full and partial throttle under heavy loads. If I hear that other than briefly when a motor is starting I figure that I have to reduce to load within 15 minutes or so. I'm not certain that's a reliable procedure but it's the only one I have.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Power stability with PTO generators
You can connect your generator through a second breaker in the panel. This is a good added insurance policy and you can select the style and capacity of the breaker to set whatever protection point you want.
I would select a two pole breaker rated for 4 amps per KW of power generated or the nearest standard value. So for 5KW of Continuous power generation I would use a 20 Amp two pole breaker connected to the 220/240 VAC outlet on the generator. A breaker sized this way will allow for some peak running. For additional safety, you can reduce the size of the breaker. A 15 amp breaker will handle a 5KW generator connection for a significant period of time.
The type of breaker used is important. Typical breakers can handle high overloads for a significant period of time. Some breakers are rated for 200% rated capacity for 1 hour. Others will trip at 125% after a few minutes. The second type is better for protecting a generator. These are used specifically to protect electronic equipment rather than general purpose or motor circuits.
Depending on your codes, this may be a breaker in your main panel, or it might have to be a small separate panel installed with your transfer switch. Remember to connect the neutral to handle unbalanced loads on 110 VAC.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Power stability with PTO generators
Murf, ya sure do think they would put that little feature on all of them. I guess it makes too much sense, or their just tryin to save the 10 cents ! The Generac I bought made a big deal out of that feature on the literature, But then they put it in Bold print like it was a real big deal that they were "giveing" you a "free" quart of oil for the empty crank case, go figure. Dave
|
|
Add Photo
Bookmarks: |
|
|
|
|
Power stability with PTO generators
Yeah, I wish my genset had that idle down feature. I'm curious to know in the real world how much it would actually save when used as a standby generator. The savings would be whatever extra fuel is required to run at a no-load 1800/3600 rpm vs. a no-load idle speed of, what, 800? Probably not all that much savings. Still, every little bit counts and why waste fuel?
|
|
Add Photo
Bookmarks: |
|
|
|
Gas Generator Weather Protecti
08-21-2003, 11:58 
Pics
Reply
Digg It 
Del.icio.us 
