PTO generator at max torque or max HP?

[Sawyer Rob]

I have a 15kw pto generator and I've run it with a 12.5 pto hp tractor quite a bit. I just don't pull more than 6kw out of the generator when on THAT tractor.

No problems at all doing so, it works perfectly...

SR

 

[Chilliwack Murray]

Just a note on a previous post - you can be 10% undervoltage and most things won't care but motors will run hot and likely trip their overcurrent protection - if there overcurrent doesn't trip however you may we damage the motor. Up to 10% overvoltage isn't good but it's not much of a concern.

10% under or over frequency however is damaging to all sorts of modern electronics. Steady state frequency should be maintained between about 59 and 62Hz to prevent damage. Many electronic power supplies and UPSs won't function outside of 59-61Hz. Momentary excursions when load changes are not a huge concern but you'll find some devices may restart and UPS's will be switching on and off battery supply and eventually go dead.

One other item when using a PTO generator on a smaller tractor... Smaller and especially older tractors are not designed for unattended operation and have no automatic engine protection shutdown. If you lose oil pressure or overheat and you aren't there to stop it you lose an engine. It's cheap and simple to add a low oil pressure switch and a high engine temperature switch to shut off the fuel solenoid like a standby engine has There are also premade protection units and switchgauges like Murphy gauges that have built in adjustable contacts for this.

 

[tbarrick]

Choosing not to go full nerd tends to cause someone to be full mechanic.....

 

[bavrit]

V is spot on with the HP rating. I run PTO generator all the time. I found when a big load turns on, like a well, or AC unit, I need the higher RPM. Otherwise the voltage will have a sag because the tractor will drop too many RPM.

 

[norshud]

I have always understood you must run at the rated input RPMs of the generator and it takes 2 PTO(not engine) HP per 1 KW of electricity.

 

[bdhsfz6]

I just bought a 15K watt generator which I will be putting on a 12K watt circuit. I will be attaching it to a Mitsubishi 180D three cylinder diesel tractor. The tractor has a three speed PTO. Running at the standard 540 setting, the engine will run at 2200rpm which is close to the max horsepower speed. If I run the PTO at the mid setting, then the engine will run at 1600rpm which is close to the max torque speed for this engine according to the owners manual. Which option should I choose for stable sustained operation?

I ran an 18KW PTO generator behind my old Kubota L3430. The tractor put out 27 PTO HP at 540 RPM. It worked fairly well with loads less than 12KW. At higher loads, the engine would slow, dropping both the voltage and frequency. As others have mentioned, this caused problems with motors & electronics. The combination was workable but I had to constantly monitor the engine RPM when large loads like pumps, oven, stove, A/C etc. were on line.

IMO, your setup will work using 540 RPM as long as you monitor & regulate large loads. I wouldn't push it past 10KW though.

BTW, I'm 20 miles east of you in Honesdale. I'm frequently up your way riding my bike on the rail trail. What is all the excavation going on just east of Forest City??

 

[nepa]

Yes Woodstock Walt, it is an old Winco that was never used, just sitting in a barn, no pto shaft attached, that I bought for $500 plus about $200 for a new pto shaft. I tend not to put much stock in what manufacturers call horsepower. This 180D outperforms my Kubota BX2660 26 horsepower diesel tractor in every way. Plus it is close to 25 years older. I had a 28 hp Jinma that had twice the power of either of them. I tend more to consider engine displacement. I have a stand-alone that is rated 7000 watts running and 8750 surge with a 420cc single cylinder gas engine. The 180D has 3 cylinders and over twice the displacement in a very torque rich diesel. Time will tell when I actually need to put it to use - if ever, and with luck will not need to. Look next week when I attach pics.
For other people who I greatly appreciate you replies, there is no meter for cps, just voltage. I hope not to go over 10k watts anyway.
Hi to bdhsfz6. I have not seen the excavation and do not know anything about it. My parents lived in Pleasant Mount and are burried there.

 

[workinonit]

A voltmeter is likely all you would have. That's what mine has. Freq and voltage are directly proportional if a gen is not syncronized anyway.

 

[Mudfarmer]

My PTO generator can produce more electrical power than my tractor is capable of producing mechanically. That simply means my tractor is the limiter, not the generator. I still have plenty of power to spare if I am a little careful. So quite rationally I do things like turn off the heat pump and rely on the gas furnace and wood stove. Turn off the freezer and refrigerator at startup then start them separately to avoid combined surge loads. I check the frequency meter on the generator and adjust the RPM of the tractor after each refrigeration unit is restarted. Since all my lights are LED at this point their power consumption is negligible and I cook with natural gas. Don't use the big screen TV on generator (too expensive). Use a laptop instead which is already set up to take variable voltages (look at its brick). And I turn the tractor off at night (seldom gets that cold in Western Washington). What I don't have to do is fiddle with a small engine all the time to make sure it is still running when I need it. Nor do I have to keep gallons of expensive no-alcohol gas sitting around getting stale. I always have diesel. My generator sits in the back of the shop with stuff piled up on it. I pull it out every two or three years when I need it, check the oil (it's always fine), plug it in and power up. Way easier than pulling the rope on my Powermate.

 

[Ken Kegris]

I have a CK25 with rated HP is 22 at 540 But with the pump turned up it easy will handle a 15KW gen set. The CK25 has a gov drop of about 200 and I dont run out of power but I have to bump the throttle up slightly to keep the freq correct. I have tried to run the CK25 on the high speed power take off and it dont seem to have when I want full power, If you are using a small amount of power its a way to save fuel The rpms is about half. I also have a CK2510 which handles the genny better than the CK25 and has a gov drop of about 50 RPM and you are not bumping up the throttle and I have not messed with the pump and it carries the 15000 watt load just fine. 746 divided into 15000 is 20.10 so that is power needed for 15000 but there not much allowance for surge I have some but you have too manage loads.