PTO generator at max torque or max HP?

[Sawyer Rob]

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.

That works every time on paper, but it doesn't in real life!

SR

 

[Ken Kegris]

It works for me, Like I said you need to manage your loads I use 3 4800 watt heater elements and a 1500 watt heater turned on low and have no problem, Runs my whole house.

 

[Sawyer Rob]

The 746 doesn't account for parasitic losses. You cannot use that number to figure out the MAX you can get out of your tractor.

That doesn't mean the generator won't work, it just means you can't use that number to find the MAX...

SR

 

[dcarman]

A generator has to be run at a very specific rpm. Frequency will be to high or too low if not. There is nothing that will kill electronics faster than bad frequency. 60 hz or death for most electronics and electronic controls here in the USA.
Generators generally have very good speed controls to maintain rpms exactly. A tractor doesn't have a good a governor on it to begin with then to try and run the generator with an underpowered tractor for the job is a recipe for disaster. The tractor should have 30- 40 % reseerve power to handle Inrush loads from such things as motors starting or the such. To small a tractor would not be recommended! Bad idea!

 

[sea2summit]

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.

Difference between you and the OP is he is not planning usage around the limiting factor of the tractor.

 

[can do]

If I'm looking at the correct tractor you have 15.5 PTO HP so 12KW isn't possible in any configuration. It might support a 12KW surge load but I wouldn't want to plan on it or do that to the engine very often.

Hey sea2summit I've a ? about pto generators & anybody else who wants to jump in feel free ! I'm considering buying a pto generator from Northern tool & Equipment , Here are some of the specs it's a North Star 12,000 rated watts 13,000 surge watts 24 HP required ,540 rpm . It will be hooked up to a 2018 M-F 1526 rated at 24.8 HP & 20.1 at the pto at 540 rpm, Would this do the job as far as the tractor? & I already did the home work on what is needed to run certain necessary items in the house & this would be more than enough.

 

[LittleBill21]

Hey sea2summit I've a ? about pto generators & anybody else who wants to jump in feel free ! I'm considering buying a pto generator from Northern tool & Equipment , Here are some of the specs it's a North Star 12,000 rated watts 13,000 surge watts 24 HP required ,540 rpm . It will be hooked up to a 2018 M-F 1526 rated at 24.8 HP & 20.1 at the pto at 540 rpm, Would this do the job as far as the tractor? & I already did the home work on what is needed to run certain necessary items in the house & this would be more than enough.

your not going to get full power as stated above, its roughly 2 pto hp per kilowatt, thus the 24hp requirement for the full wattage.

your looking at around 10k max, maybe a touch lower.

 

[sea2summit]

Hey sea2summit I've a ? about pto generators & anybody else who wants to jump in feel free ! I'm considering buying a pto generator from Northern tool & Equipment , Here are some of the specs it's a North Star 12,000 rated watts 13,000 surge watts 24 HP required ,540 rpm . It will be hooked up to a 2018 M-F 1526 rated at 24.8 HP & 20.1 at the pto at 540 rpm, Would this do the job as far as the tractor? & I already did the home work on what is needed to run certain necessary items in the house & this would be more than enough.

There’s folks in here much smarter than me, but general rule 1.5-2 HP per KW is what you need. There’s an exact HP to KW conversion but you need to account for all the mechanical loss before you get power to the generator (PTO shaft, bearings, etc). So 2HP per KW is safe, 1.5 HP to KW is probably possible. Obviously when you go to bigger units you probably have to worry less about mechanical loss so 1.5 HP to KW becomes very achievable. But like I said, I’m not overly smart on it.

 

[LouNY]

My only concern with the gen sets from Northern is that most of those are 2 pole units that need to spin at 3600 rpm,
so the step up gearing from 540 to 3600 rpm is quite large, 6.666 to 1.
The 4 pole heads only need 1800 rpm so the gear box is only running a 3.333 to 1 ratio.
I have seen some of the other brands of small pto generator heads with the 2 pole generators and they are not as stable as the 4 pole units
even in the same size range.

 

[can do]

My only concern with the gen sets from Northern is that most of those are 2 pole units that need to spin at 3600 rpm,
so the step up gearing from 540 to 3600 rpm is quite large, 6.666 to 1.
The 4 pole heads only need 1800 rpm so the gear box is only running a 3.333 to 1 ratio.
I have seen some of the other brands of small pto generator heads with the 2 pole generators and they are not as stable as the 4 pole units
even in the same size range.

The only thing I'm mainly asking is 24 HP enough? & all it states is required HP 24 HP. & I guess that's engine HP not HP at the pto & it doesn't state that is required at the pto & that was at 540 rpm only required with 24 HP or more .

 

[LittleBill21]

The only thing I'm mainly asking is 24 HP enough? & all it states is required HP 24 HP. & I guess that's engine HP not HP at the pto & it doesn't state that is required at the pto & that was at 540 rpm only required with 24 HP or more .

we answered your question. its 10k with that tractor. its 24hp pto for full rating. they would have no idea what tractor /loss the engine to pto conversion would be.

 

[can do]

we answered your question. its 10k with that tractor. its 24hp pto for full rating. they would have no idea what tractor /loss the engine to pto conversion would be.

Okay! Thanks for the clarity & that would be 20.1 HP at the pto = 10K .

 

[sea2summit]

Okay! Thanks for the clarity & that would be 20.1 HP at the pto = 10K .

FWIW my 11KW unit came with a 23HP engine who's drive shaft runs pretty much straight to the generator, can't say for sure I've ever put a 11KW load on it but just for reference.

But yes, 20PTO HP should do fine with 10KW.

 

[can do]

FWIW my 11KW unit came with a 23HP engine who's drive shaft runs pretty much straight to the generator, can't say for sure I've ever put a 11KW load on it but just for reference.

But yes, 20PTO HP should do fine with 10KW.

Okay ! Thank You for your help with this question as I'm new to the idea of a pto gen. so I guess I'll have to go with less , My other tractor could handle it , It's gasoline & would consume way more fuel than the diesel. Thanks again.

 

[Mudfarmer]

Maybe you all should work backward. Check your electric bill. In the summer I average less than 10 kilowatt-hours per day, in the winter maybe up to 20. Thats over daytime hours so 1- 2 kilowatt-hours per hour. That means a box store 4000 watt gas generator is just fine for my needs (and most other households or they wouldn't be popular). My 20 HP (at the PTO) tractor gives me 10,000 watts hooked up to my 15,000 watt capable generator, but I really need only about 2000 of that on average (the other 8000 is wasted diesel but I have to run almost wide open to generate the RPMs up to stay at 60cpm), thus plenty to spare for surges. Take a look at your power bills. 15 kw generators were designed for dairy farmers who HAVE to milk (ie run their energy consuming milking machines).

 

[Sawyer Rob]

but I really need only about 2000 of that on average (the other 8000 is wasted diesel but I have to run almost wide open to generate the RPMs up to stay at 60cpm), thus plenty to spare for surges.

Not exactly, if the engine isn't working to make the 8000, it's not burning the fuel to make it either...

SR

 

[Mudfarmer]

SR you're right. That's why I only have to refill the tank once late in the afternoon running my generator. The extra 8000 isn't produced without a load and the fuel isn't burned (minus inefficiencies in the system). The capacity is there were I to need it, but I really never need that much. This is analogous to mowing short dry grass vs wet heavy grass; the high load of the latter requires more energy and takes more fuel. Doesn't change my point though - most households don't draw much more than a few thousand watts so don't really need a full 15KW output.

MF

 

[Vigo327]

It's true that you have to make enough power to spin the engine at that speed even if you don't need much power out of the generator because you have to maintain rpm regardless to keep frequency in a safe range, but.. in a diesel (and this is one of the if not THE biggest advantage of a diesel) when you don't need power out and are just trying to keep the engine spinning you can use ONLY as much fuel as it takes to spin the engine.

That's a lot better than a gas engine which has to overcome its frictional requirements AND run enough fuel through the cylinders to maintain an 'ignitable' mixture. Because ignition comes from a single point and has to propagate through the cylinder, even when you don't need much power out of a gas engine, you still have to feed it more fuel than you would 'need' just to keep it spinning, and then throw most of the power potential out the window by restricting the air inlet and limiting ignition timing to maintain low rpm with 'too much' fuel for the load.

So compare the 'waste of diesel' to what a gas generator does and it doesn't look so bad. Gas generators are bad enough that one guy used the 12v circuit of his Toyota Prius (roughly a 1kw 'generator') and found that his 1500cc Prius engine was more fuel efficient making ~300v and converting it back to a pittance of 12v and converting that back up to 120v ac, than an actual 1000w 3600rpm governed gas generator. A 1kw gas generator is going to have a <200cc engine.. non-inverter gas generators SUCK efficiency wise.

If you're going to have a non-inverter generator at all, it might as well be diesel as its a lesser of evils.

 

[Sawyer Rob]

One thing I'll add here is, using a bigger generator head has the BIG advantage of more mass, and that's a good thing in MANY ways...

Of course, as a heat sink, but one big advantage for a bigger gen on a smaller tractor is, the extra rotating internal mass of the generator. It works like a flywheel, absorbing sudden loads as they come on, giving your engines governor time to cover the load.

I'll have to say here though, I've NOT had even one modern tractor, that the governor didn't respond fast enough to properly run my pto generator.

SR

 

[CobyRupert]

Maybe you all should work backward. Check your electric bill. In the summer I average less than 10 kilowatt-hours per day, in the winter maybe up to 20. Thats over daytime hours so 1- 2 kilowatt-hours per hour. That means a box store 4000 watt gas generator is just fine for my needs (and most other households or they wouldn't be popular). My 20 HP (at the PTO) tractor gives me 10,000 watts hooked up to my 15,000 watt capable generator, but I really need only about 2000 of that on average (the other 8000 is wasted diesel but I have to run almost wide open to generate the RPMs up to stay at 60cpm), thus plenty to spare for surges. Take a look at your power bills. 15 kw generators were designed for dairy farmers who HAVE to milk (ie run their energy consuming milking machines).

Using total energy used (kw-hrs) to determine an “average” power usage means nothing when sizing a generator, or any electrical sizing problem. Instantaneous power required is the only thing that matters.
Example: I want to run my 4000watt hot tub on a generator. It only runs 3 to 6 hours a day (12-24 kw-hrs per day). That’s an average 500-1000 watt load for 24 hours, so a 1500 watt generator should be more than enough right?
Or, say it is “daytime loads” for 12 hours, like you did, and we say the average is double: 1000-2000 watts, we buy a 3000watt generator? Still won’t work.
A generator needs to be sized based on running loads and to accommodate motor starting inrush currents. It has to be sized to start that motor when other loads are already running unless there’s a plan or interlocks for sequenced starts.