PTO Alternator question

[M Nut]

It rarely is needed, so I don't think about it very often. But, a few weeks ago we were without power for two days. So, here's my thoughts........it is a 540 rpm alternator, but when running the power for the farm I need to have a 540rpm tractor running at high engine speed to achieve that 540rpm. Could I use an adaptor and use my 1000rpm pto tractor and run the engine at basically half speed? The alternator has a gauge with needle that shows where alternator needs to be running. I think my 95hp tractor would run the alternator easy at half throttle using 1000rpm pto. Anyone have any experience with this idea?
Thanks

 

[Janicholson]

It is a great idea and commonly used. adapters are available. I would put a clamp or visegrip on the throttle (or big note to self) that limits the throttle movement. Generators do not like more thaan 2X speed, and homes dont like 500 volts at 150cps. Jim

 

[55 50 Ron]

I'm WAY behind the times, but I thought modern tractors have both PTO speeds available. Or maybe that was just a certain era and new tractors are just 1000 RPM?

Sorry for my lack of knowledge here.

 

[M Nut]

Great idea on the clamp/vice grips. So far I have not run the alternator through the night, so I am aware of what the tractor is doing. But, if ever I would run it while sleeping or away from the yard, that's a good idea. Thanks for the thoughts.

 

[M Nut]

My tractors are old My "newer" tractor, with dual speed pto, is an 886IH from 1978! I do have a 2005 Massey Ferguson, but that one I only have the 540rpm shaft for. So, the IH it will be.

 

[JDEM]

Just a rough guess, but a tractor rated for 95 HP at 2200 RPM likely makes around 35 HP at 1100 RPM. So it is a matter of how big your PTO generator is and how many amps max do you need? I assume at 1100 RPM you can make 17,000 watts with no problem.

 

[M Nut]

25kw / 35kw according to the sticker on the alternator. Don't need to run everything, just the well pump to water cows, and heat in the house if cold. Refrigerators and freezers, and a few lights. 40hp at 540rpm has done it fine in the past.

 

[buickanddeere]

Every now and again somebody thinks of this "new idea". Maybe ok if the only loads are lights, a fridge, freezer and a sump pump.
Problem is the governor response will be lousy.
If 1000 pto rpm is 1900, then 1026 is required for 540. She is going to wet stack at those rpms all night.
HP will be closer to 25HP than 50HP at 1026rpm.
Have to wonder how many hundreds of dollars over a couple nights that you are planning to save ?

 

[David G]

You will be fine, I have a frequency setting on my multimeter, easy to get RPM right.

 

[M Nut]

True, I just thought running half throttle on an engine is easier on it than full throttle, but maybe I'm mistaken. You're right, two times of use every ten years isn't going to be a deal breaker money wise. I'm just
thinking today............may or may not be a good idea.

 

[John T PS]

Sure the idea sounds great and if it works okay go for it, however this old rusty engineer has a few things to consider:

1) The tractors HP is a function of Torque X RPM, therefore at 1/2 RPM its not developing the HP rating if at full throttle.

2) The Generator isn't 100% efficient, the tractor has to put more HP in then you're getting out of the generator in the form of electrical energy.

3) The answer depends on the tractors HP at X RPM and if that suffices for your load,,,,,,,,,,The efficiency of the Genset,,,,,,,,And most important the load you put on the genset as well as the RPM and frequency regulation and governing the tractor and genset can provide if loads suddenly change.

Sure give it a try its impossible to tell from here not knowing any loads or efficiencies or HP at X RPM etc etc etc but hey I like the IDEA if it works out

John T

 

[Bob Bancroft]

My alternator is a 25/15. It will just barely start the old 10 HP centrifugal fan on my bin dryer. That's what I bought it for- in case I got a bin full of wet corn, and the power went out! I've never needed it for that reason, but have run it over night to power the house. A 50-60 HP tractor will start the 10 HP motor. The 4020 running on the 1000 RPM shaft won't- just not enough power at the low engine speed. I have several smaller tractors, and they are what get used on the alternator. Used to be an AC C, which isn't cranking very fast at PTO speed anyhow. Now a Case VAC is hitched to the alternator all winter. I have another, 40 HP gas tractor, and a little New Holland/Fiat diesel which is very frugal on fuel, which has run the alternator also.

 

[M Nut]

Good to know. I've got no shortage of gas tractors in the 40hp range. Maybe I'm better off just using one of those in the rare instances when needed. Thanks for the feedback.

 

[M Nut]

You're right. I should just try it out on a nice day when I have time to see how things are working. That way I'm not trying something new in bad weather and higher stress situations. Trial and error will tell a lot of the story.

 

[miangus]

Another thought, running a large expensive diesel unattended unless you have some kind of safety switch could be an expensive proposition if something goes south. A rebuild in a farmall M much cheaper than an 1066.

 

[M Nut]

Well, that is true too......... good thought.

 

[Brendon-KS]

Tractor engines are designed to run for many thousands of hours at their full rated speed so that won't hurt the tractor at all. I would guess that a smaller tractor running at full rated engine speed putting out 30 hp on its 540 rpm shaft will cause less engine wear and tear than a larger tractor delivering the same 30 hp but running barely above idle to spin its 1000 rpm shaft at 540.

 

[M Nut]

Ok, good to know. I appreciate all the opinions I am getting. Lot's of good thoughts.

 

[John T PS]

Hey good luck, if it works at that sweeter lower RPM Great

John T

 

[P I Pete]

I have a Farmall M with a nine speed if I need to run generator I put M in over drive as that speeds the PTO, plenty of power and about 1/2 throttle.

Pete

 

[Fordy20]

A PTO generator needs to run at 60 Hz. And that?s determined by the RPM on the PTO shaft. If it doesn?t run at 60 Hz your appliances will either act funny or may not work at all.

 

[Mark-Mi]

I have done it with my JD 4020, but I think its kind of hard on it. Carbons it up.