PTO generator
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daybreak1998
Silver Member
Howdy,
The alternator portion of a generator come in a few different flavors.
Of course the main one here would be a single phase. There is of course 3 phase as well.
There are 2 pole alternators which need to spin at 3600rpm to make 60Hz 240volts current. That is why so many small engine which run in the 3600rpm range are direct connected to the alternator. (no gearing) Then you have a 4 pole alternator which spins at 1800rpm. (more expensive, considered heavy duty, commercial grade) Which is why so many generators which are diesel, have 4 pole alternators attached.
PTO generators = have gearing, smaller units known as residential spin internally at 3600rpm. So that 540rpm pto needs gearing to get it to 3600rpm. The larger pto generators have 4 pole alternators and spin at 1800rpm. They still have gearing to get that 540rpm pto to 1800.
The main thing to consider is this. Anything running at 3600rpm is going to make noise. Think about a car on the highway doing 60mph in second gear. Its redlined and sounds like it going to blow up. Imagine driving across country like that. Will that engine make it? That is why the slower spinning engine and alternator will last longer. They are also more expensive. The only quiet generator spinning at 3600rpm is probably the Multiquip Whisperwatt 7000. Small diesel running at 3600rpm and alternator head at 3600rpm.
A PTO operated implement can be run at different speeds. A PTO Generator needs to spin at the proper speed to make that 60Hz 240volts.
You can take a look at this you tube video which shows them putting load on a smaller PTO generator. It lugs down the engine pretty good.
Small tractor with 15KW pto generator which spins at 3600rpm. So you have the tractor noise and the generator noise.
The alternator portion of a generator come in a few different flavors.
Of course the main one here would be a single phase. There is of course 3 phase as well.
There are 2 pole alternators which need to spin at 3600rpm to make 60Hz 240volts current. That is why so many small engine which run in the 3600rpm range are direct connected to the alternator. (no gearing) Then you have a 4 pole alternator which spins at 1800rpm. (more expensive, considered heavy duty, commercial grade) Which is why so many generators which are diesel, have 4 pole alternators attached.
PTO generators = have gearing, smaller units known as residential spin internally at 3600rpm. So that 540rpm pto needs gearing to get it to 3600rpm. The larger pto generators have 4 pole alternators and spin at 1800rpm. They still have gearing to get that 540rpm pto to 1800.
The main thing to consider is this. Anything running at 3600rpm is going to make noise. Think about a car on the highway doing 60mph in second gear. Its redlined and sounds like it going to blow up. Imagine driving across country like that. Will that engine make it? That is why the slower spinning engine and alternator will last longer. They are also more expensive. The only quiet generator spinning at 3600rpm is probably the Multiquip Whisperwatt 7000. Small diesel running at 3600rpm and alternator head at 3600rpm.
A PTO operated implement can be run at different speeds. A PTO Generator needs to spin at the proper speed to make that 60Hz 240volts.
You can take a look at this you tube video which shows them putting load on a smaller PTO generator. It lugs down the engine pretty good.
Small tractor with 15KW pto generator which spins at 3600rpm. So you have the tractor noise and the generator noise.
yeh that was a great point and it was something I would have never thought of. I have some roller bearings and mounts for pulley shafts if I needed them. If it required some type of true tolerances not easily acheived with that then one could actually just use a case from an identical engine. Even though I probably have cases for that I may not go that far cause it would probably look stupid.
I hate giving up and I haven't yet but I'm starting to wonder. That bigger one I have probably doesn't have the single bearing.
PioneerMan
Silver Member
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Another point I haven't seen made is your 31hp engine will not be making the 25ish hp required to 'fully' run a 12kw genny at under 1k rpm. I guess it depends on how light of a load you're looking at...
Soundguy
Old Timer
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- RK 55HC,ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC
keep this in mind. running your tractor at a low rpm is running it OUTSIDE it's prime power band. that means you will have less hp.
also.. you will need to get the gear ratio correct to run the genny head to get correct output freq.
also.. fuel usage will DIRECTLY depend upon kilowatts of electricity being used ( load )
doesn't really matter what 'unloaded' fuel economy you are getting.. when loaded.. that will be the difference. nothing is free.. fuel has 'x' amount of energy.. and it will be less than perfectly converted to rotational, then electrical.. in a lossy process that will roughly consume 2pto hp per KW generated.
soundguy
also.. you will need to get the gear ratio correct to run the genny head to get correct output freq.
also.. fuel usage will DIRECTLY depend upon kilowatts of electricity being used ( load )
doesn't really matter what 'unloaded' fuel economy you are getting.. when loaded.. that will be the difference. nothing is free.. fuel has 'x' amount of energy.. and it will be less than perfectly converted to rotational, then electrical.. in a lossy process that will roughly consume 2pto hp per KW generated.
soundguy
someone tell me if this calculation is right. If you ran a 540 RPM PTO to run a 3600 rpm generator you would need about 7 to 1 and a 14" inch sprocket to a 2" sprocket. I say sprocket because it would probably need chain driven because 2 " would be too small for a pulley with a load like that. Seems like a cheap 3600 rpm generator might make the project ridiculous. If that calculation method was right then an 1800 rpm generator would be about 3.5 to 1 or 14" and 4" pulleys or 12" and 3". That doesn't seem right. If it is right then maybe 14 and 3 would be good so you could run the tractor slower? Is tractor rpm linear to PTO rpm? In other words if it's 540 at 2600 rpm would it be 270 at 1300?
Last edited:
Todd727
Gold Member
You have to count teeth if using a chain. For example, a 60 tooth sprocket would match up with an 9, which is a little tight and would probably wear the chain prematurely. A 12 tooth would be about the smallest, which would perfectly yield an 80 tooth. You need to find a ratio that is equal to 6.666667 between the smaller and larger sprocket for exactly 540 to 3600.
Here is a calculator. It's made for motorcycles. If you set the standard to 12 front, 12 rear, 3600 rpm and set the speed to anything, because it's not useful to your problem, then you can try different size sprockets in the new section to reduce to 540 rpm. Remember that you will be putting the large sprocket on the front or driving shaft.
http://users.tpg.com.au/jono794/tools.htm
Here is a calculator. It's made for motorcycles. If you set the standard to 12 front, 12 rear, 3600 rpm and set the speed to anything, because it's not useful to your problem, then you can try different size sprockets in the new section to reduce to 540 rpm. Remember that you will be putting the large sprocket on the front or driving shaft.
http://users.tpg.com.au/jono794/tools.htm
Soundguy
Old Timer
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- Tractor
- RK 55HC,ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC
and if belting.. figure slip too..
