Generator 3 Pt generator.

[Zork]

Hi all! I have a 35 hp tractor with a 2 speed pto (540 and 1000 RPM) The generators I have been looking at are 540 rpm input. Now my tractor engine will run @ 2600 +- rpm for a pto output of 540. Can I put the pto in 1000 rpm and run my tractor engine at half of the 2600 rpm so that the generator input is still 540? The reason I ask is that some people that I have asked said their tractors burned too much fuel to make the generator worth using and so my tractor at 1600 rpms burns a gallon of fuel an hour. Will this work?

 

[schmism]

it would be better to run it at the 1000 pto speed as it means a lower RMP for you tractor.

BUT you need to keep these 2 things in mind.

1) the genny head wants to spin at about 3600 rpm to output 60hz power (which is important). There are excpetions such as a genny head wired for 1800 rpm input's but those are EXPENSIVE.

2) it takes roughly 2hp per 1Kw of output. You need to get an idea of what hp you tractor will output at half rpm as its not the same as at 2600 rpm (which is were your 35hp rating is likely to come from) so this can limit the size gen head you can run.

in short, you can not spin a 3pt gennerator (designed for 540 imput) with the 1000 rpm range on your PTO. Youll have to build your own gear box to supply a raw generator head with the proper speed.

 

[patrick_g]

The manufacturer usually supplies or will supply on demand the lowest RPM at which you should "work" your tractor. Some of the smaller diesels have to run fairly high RPM to make their HP. My 40HP spins at 2600 to make 540 PTO. You shouldn't work my tractor at RPM under about 16-1700. Just putting along is no big deal but if you want to do some REAL WORK you want to be above 1700.

In my case I have no 1000 RPM option BUT if I did and throttled back to get 540 out of the 1000 gearing I'd be turning 1400 RPM. Not enough R's to deliver useful work. The HP falls off with reduced RPM so even if you could work your engine at the RPM required, it might not produce the HP required to drive a genny head to the output you need/want.

Another downside is if your tractor is your generator, during power generation, you don't have a tractor. That may or may not be a concern depending on yoiur circumstances and needs. I was thinking of getting a genny head and control panel and building up my own 3PH genny but it doesn't fit my requirements since I am a one tractor guy.

Pat

 

[Farmerford]

fjb2c:

I bought a PTO generator several years ago for a 28 PTO hp tractor and researched the same issue, because I wanted to run the engine at about 1/2 the rated RPM of 2600. The principal problem is maintaining constant PTO speed with changes in electrical load on the generator. It seems that tractor governors operate well only in the high end of the RPM range. At about half engine rated speed a governor allows a great change in RPM before it responds by increasing fuel if the load is increasing or decreasing fuel if the load is decreasing. I found some charts of an actual test. They showed a large (10-15% I recall) drop in RPM and therefore frequency and voltage when a subsantial load (say 1/2 the generator capacity) was applied to a 540RPM generator that was being run by a 1000RPM tractor at half speed. At those low speeds/power settings the governor was not responsive enough to keep PTO rpm steady over changes in load.

In contrast, the same tractor running the same generator (except with a gearbox for a 1000 RPM pto), so that engine RPM was in the governed range of ~2400 RPM, showed almost no change in RPM when a load was applied.

If the electrical load were constant, then you could manually change the fuel setting to get the correct RPM. But in my case I was using the generator to power a welder, air compressor, and power tools doing on-site work and the loads varied constantly.

 

[bucmeister]

I have contemplated this very issue because of fuel consumption just as you bring up and have arrived at a couple of conclusions. The first would be my load which could vary greatly, for example, we have survived well enough on a 4KW Coleman gen since right after an ice storm in 1989, however if we want to heat up the hot water everything else has to be shut down for a couple of hours and there is no way it will run the central AC, so for those times that we have been out in the summer, such as after Katrina, it can get miserable.

My 5300JD will pull a fully loaded 25KW @540 and with the torque curve that the engine produces @1700 engine 1000PTO would likely make 10KW dependably. So it would depend on the anticipated load.

This longwinded answer is my way of saying I think it would depend on your load expectations and the size of your genny. The more overkill your generator setup is for your actual task the more likely you can use the high pto setting. At least that is my guess and what I would try if it were me.

 

[zzvyb6]

Not recommended. The governor won't track properly and could possibly go unstable if the torque curve is flat The greatest problem is with motors, like a well, a/c compressor or air compressor, with high draw an sudden disconnect. The tractor rpm will be slow to adjust at the reducedpto speed. This will overspeed and underspeed the voltage and phase (frequency)response of the alternator output, risking the windings in the electric motors. If you ant to save diesel, shut off the tractor periodically. Biggest problem I have is noise telling the cruisiing neighbors I have power. This usually means water,, so they line up with their trailers holding water troughs. Leave a bucket there for fuel donation$. The biggest thing I've learned with my pto alternator is that there will be a run on gas-station gasoline when the power goes out for an extended period of time. With so few diesel vehicles around, the diesel pumps will still have a supply. You need to locate stations which have their own stand-by power.....

 

[zzvyb6]

Not recommended. The governor won't track properly and could possibly go unstable if the torque curve is flat The greatest problem is with motors, like a well, a/c compressor or air compressor, with high draw an sudden disconnect. The tractor rpm will be slow to adjust at the reducedpto speed. This will overspeed and underspeed the voltage and phase (frequency)response of the alternator output, risking the windings in the electric motors. If you ant to save diesel, shut off the tractor periodically. Biggest problem I have is noise telling the cruisiing neighbors I have power. This usually means water,, so they line up with their trailers holding water troughs. Leave a bucket there for fuel donation$. The biggest thing I've learned with my pto alternator is that there will be a run on gas-station gasoline when the power goes out for an extended period of time. With so few diesel vehicles around, the diesel pumps will still have a supply. You also need to locate stations which have their own stand-by power.....

 

[patrick_g]

I was in a NATIONAL DISASTER AREA due to an ice storm. None of the stations had power, grid or genny. Those who were prepared had hand pumps to draw fuel up out of the underground tanks into 5 gal cans for measuring. The Army came in with big truck mounted electric plants but they were used only to preserve the food supply at the supermarket.

LPG and diesel are both good choices for standby genny operation as they can be stored longer than gasoline. STABIL extends gasoline life but not so as to compete with diesel with storage additive. LPG has no storage life limit (it is already a jillion years old!)

A generator on a tractor PTO is better than no generator unless it fries something expensive or important like, say a submerged well pump supplying your drinking water and stock water or yoiur frige or freezer or big screen TV. There are nice portable generators that allow you to interconnect another unit for more power. What versatility! If you need power in two places you have it. If you need a lot of power at one location, connect two together. If one fails you have a redundant backup.

I suggest that a Prius or a GM pickup are better options than a tractor running a PTO genny.

Pat

 

[Soundguy]

I agree witht he others.. your tractor turning hlf rpm will not be making 'half' power.. probably much less.

Besides.. fuel burned will also be a factor of work performed.. if you are running a high electrical load.. you are going to be burning some fuel... pay me now or pay me later.

Your tractor was designed to run at rated rpm for extended periods of time.. let it do it's thing.

Soundguy