Author Topic: A PTO driven Generator?  (Read 5661 times)

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Offline m12ax7

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A PTO driven Generator?
« on: January 22, 2012, 10:04:54 pm »
I have a Kubota tractor (BX1850) with a "Category 1" three point hitch.  It has a 18hps diesel and it's PTO is rated @ 13.7hps --540rpm @ 3142 engine rpm.

I've seen/heard of commercially available PTO generators for larger tractors but not tied to any Kabotas. 

I currently own a Generac 4000xl,  which is now several years old (but very few running hours).  I purchased it mainly/solely for running our sump pumps (3) but now I think I'd like to run our furnace (natural gas) and fridge. 

Back the the Kubota..   The question (of course) is,  whether such a project is worth starting?    I'd not mind avoiding belts and pulleys and running a direct drive from the PTO to a alternator.

I have a Kollmorgen servo motor I'd not mind using (but would need to gear up)  I don't have it's spec's handy but I think it's rated at 7.5 KW.

I really don't have a need for three phase,  but I wonder if it would be more efficient to use a three phase generator/alternator or just single phase? 

I'm unsure of the direction I'd need to go relative to the  frequency/voltage/throttle interface.  I'm guessing using a pair of 6L6's or 6SN7's and a motor from a Dual 1249 won't do?

I still plan on using the tractor for cutting my lawn and plowing/blowing snow,  so the throttle control has to "piggy back" the "gas" pedal.  or at least be a "very quick" disconnect. 

I understand that I'm not supplying a whole lot of information here,  but this is just a "is the project worthy" question and not so much as "how to".

I've not heard a whole lot of Kubota engines and wonder if they are suited for this purpose?

Ya or Nay?   opinions?

Offline Janne

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Re: A PTO driven Generator?
« Reply #1 on: February 01, 2012, 05:46:55 pm »
Does the cubota have hand throttle? We have a tractor PTO generator as a backup unit for longer power outages, it's 15KVA genny and we're using a 48HP valmet to run it. With that kind of power marging, the diesel pump governor is easily capable of maintaining frequency of at least 47Hz, if set for ~53Hz without load.. Most appliciances will work down to 40Hz ok, so I think it might be possible for the cubota too without any special controls.

If you're going to need to buy the generator anyway, I say buy 3 phase. The cheapest solution will be probably to get a 1500rpm (or 4 pole) generator and then use a step-up gearbox for driving it.. That's how it's been done on our PTO generator anyway. It has a 4:1 speed up drive, so a bit under 400 pto rpm are enough to run it.
Beyond the wolf border

Offline m12ax7

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Re: A PTO driven Generator?
« Reply #2 on: February 01, 2012, 09:16:33 pm »

Yes,  my Kubota has a throttle handle located on the steering column. 
My camera is on the fritz, but hope to get some pics posted in the next week or two.

Offline A of J

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Re: A PTO driven Generator?
« Reply #3 on: February 02, 2012, 01:31:41 pm »
It is hard to gleem from your post just why you need a back up generator but lets assume it is for mains failure.

Kubota enigines are widly used in gen sets, Janne was correct, that HP will cope with a reasonable size generator without too much frequency drift, say 3 Kw. The bigger you go the larger the frequency drift will be for a given throttle setting, having said that the motor has enough HP to start large loads, assuming the generator can handle it which comes back to generator design.

 I would stay with single phase unless you have need for three phase, as I guess you are proposing a back up power supply. With 3 phase generators there is the problem of phase inballance to concider, if all 3 phases are not ballanced then heating within the generator occures.

For standard PTO RPM (yours) you will need to gear up, so my advice is stay with a 3000 RPM generator (50 HZ) or 3600 (60 HZ) and a gear box, as that will be your most cost effective option. If your needs are for AC power then stay with a generator intended for that purpose.

So if a back up power supply is what you need then your Kubota is a viable option, have you thought about a PTO welder, they generally have an AC generator built in and are plug and play.  And the welders are around 26V DC so can be forced into action as a charger for a 24V battery bank, albiet with constant vigilance.

A of J