Generator PTO Generator Question

[Chuck-KY]

I'm seriouly considering purchasing a 15KW PTO Voltmaster generator. I have a 24hp lawnmower that absolutely uses gas at a alarming rate while my 790 JD sips diesel at rated pto speed compared to the gas lawnmower. I can buy a 15KW PTO generator for less than $1200 while a motor/gen set will run around $2300 and probably use twice as much fuel for an extended run time. Is there anything pro or con about the PTO/tractor combination I should know or am missing. I have a frequency meter to set gen speed with and have a smaller 6KW generator now. The governor on the small gen. is really nothing special in relation to frequency control. Really no better than on a tiller or lawnmower. I would think once speed/ frequency is set on tractor, it would have a better governor control verses the smaller gas engine, or am I missing something. I appreciate any information or experience either way in regard to the two. Thanks - Chuck

 

[JB4310]

There are alot of threads on this subject but I don't know how to link to them, I learned a great deal here while I was in the process of getting a pto gen, I got a 10 KW IMD brand.as far as the governor goes I can give my own experience, I experimented with mine on an old ford 1700 diesel and a newer JD 4310, it not just set it and go, the tractors gov will not compensate for the wide swings of 5-10 KW you will have to manually adjust throttle a little, the newer tractor was a little better but still required manual input.
If the load was constant then that obviously would be better,
Like I said there is alot of great info here, you'll have to search a little or maybe someone can link some of the threads.
Your 790 has around 30 pto hp? so 15 kw would not be to big as the gen rule is 2 hp per kw, I kinda wish now that I got the 15 kw as the heavier mass spinning probabbly makes it easier on the governor especially with a 10 kw draw, would run cooler to.

As far as the pro and con goes there's alot of that, it almost turns into a fight when really it should be just a personal preference.
this might link you to a recent discussion

http://www.tractorbynet.com/forums/attachments/129834-power-take-off-generator.html

 

[art]

Most of the time to hit the horsepower to the KW will cover you for your needs. All engines work a little different on reponse time of the load, some are quick and some are slower, some give more then enough and some are al little short on torque reponse! The two horsepower per KW should cover you! For your tester, you might not aways want to look!

 

[Soundguy]

I'd add that the larger the rotational mass of the genny and engine driving it, the less rpm/freq variation there will be when a load demand comes up.. remember the flywheel stores energy.. besides.. I'd much rather rely on the governor on my tractor than the governor on some whizz-bang (essentially) souped up gass lawnmower engine..

soundguy

 

[SPYDERLK]

The problem with many of the less expensive pto gens is the large speed increase [from 540 to 3600] that is needed. In these cases the driven gear on the gen shaft is very small. This arrangement is inefficient. These gearboxes run hot. This is an indication that a lot of power is wasted in the drive - - in the 10% range. They are still a good reliable power source, just more wasteful than a direct drive setup.
More expensive pto gensets have larger better designed gearboxes and/or use 1800rpm gens so the driven gear is a reasonable size.
larry

 

[Farmwithjunk]

I bought a PTO ALTERNATOR. Bigger HP that you're looking at, but they offer smaller pto generators too.

Medium PTO

I use the model 50/30 PTCD. Have used it behind 61HP or 95HP tractors with satisfactory results. Never used to full capacity though.

 

[Iplayfarmer]

Is there anything pro or con about the PTO/tractor combination I should know or am missing.

When that big snow storm comes through and knocks out your power, you have to choose between using your tractor to power the house or using the tractor to plow snow. You can't do both with the same tractor.

Of course if you have more than one tractor you're set.

 

[RonMar]

Where you will probably run into issues, is governor control like JB4310 mentioned. Your typical tractor governor is/does not have full authority. It only has fuel control in a narrow area around where the throttle lever is placed. What does this mean for the PTO generator user? Well if you have any really massive single loads, they may exceed the governors ability to react. Basically, the governor can't deliver enough fuel to maintain RPM for a large load increase, even though the applied load is within the engines HP capability. This is where a larger tractor might work better, as the governed range is larger in terms of HP. You of course will have to experiment to see exactly how much of an effect your major loads shifting on or off has on how well the governor can maintaion RPM/frequency.

A 15KW set is a good match for a 30 PTO HP tractor. But a 10KW set may maintain RPM better unassisted from zero to full load. Even with gearbox losses, you will probably be under .2 gallons per Killowatt per hour for fuel consumption. IE: a sustained 5KW load will cost you one gallon per hour...

 

[RickB]

When that big snow storm comes through and knocks out your power, you have to choose between using your tractor to power the house or using the tractor to plow snow. You can't do both with the same tractor.

Of course if you have more than one tractor you're set.

Anyone that can't be without power long enough to clear a driveway needs to have an automatic standby system. The difference between wanting and needing is half the trouble this world is in.

 

[BobRip]

You do realize that some appliances can be damaged by the wrong frequency and voltage. I would at least initially monitor these for each load so you know which loads present a problem. There are many variables here. For example if the generator is lightly loaded and you turn on a load you will probably have a greater voltage and frequency change then if the generator is 1/2 loaded and the same load is turned on. I don't have experience with this, but that is the theory. Does anyone here have direct experience with this? I was not sure from the other comments.