PTO generator

[PineRidge]

Correct, but you will only have 1/2 the PTO HP available to work with.

Aaron Z

On a 15KW PTO-generator the PTO speed is 540 but the gen set is runnng at over 3600 RPMs due to the gearing. At 540 RPM PTO speed my generator is kicking out 240 volts, at 60 cycles and is capable of producing 62.5 Amps

 

[Yooperman]

So, are you saying I won't have to run my tractor at 3200 rpm to get the 540 pto speed make the gen run properly.

I can only speak for my BX25 and pto generator. I MUST run my BX25 at 3142 rpm engine speed to get the pto at 540 rpm that my pto generator MUST have.

I don't know about others. :confused2:

 

[PineRidge]

I misunderstood you, I was talking PTO RPMs vs generator RPMs. I believe my New Holland is running somewhere close to 2600 engine RPM to achieve 540 PTO RPMs

 

[dex3361]

That's locked rotor amps! What happens when you lock a rotor on a motor? You blow the breaker! It's not the same as starting amps.

Motor Calculations | NEC content from Electrical Construction and Maintenance (EC and M) Magazine

" Motor locked-rotor current. If the rotating part of the motor winding becomes jammed so it can稚 rotate, no counter-electromotive force will be produced in the motor winding. This results in a decrease in conductor impedance to the point that it痴 effectively a short circuit. What痴 the result? The motor operates at locked-rotor current, often six times the full-load ampere rating, depending on the motor Code Letter rating [430.7(B)]. This will cause the motor winding to overheat and be destroyed if the current isn稚 quickly reduced or removed."

Electrical Motor Calculator

Plugging in 1 hp , 90% efficiency, 85 PF (power factor) and 230V to the calculator in this link.

You get:

1 phase = 4a.
FLA = 5A

What does FLA stand for? Full Load Amps! At full load the motor draws 5A, 230V * 5A = 1150W; 1 HP = 746W FLA for a 1 HP motor = 1150/746 or 1.54 times.

Now look at the chart for starting amps, what does the FLC state? 150% to 300% of running current and what's 300%? It's 3 times, exactly what I said. I work with this stuff everyday my systems are built on these calculations. Are you off the grid running several inverters on a daily basis?

Rob look at your pic of the starting current notice the first peak is 600% the FLA. Here is a quote from your link. "a. For full voltage (DOL) starting, starting kVA= 6*rated kVAod the motor . Use the nameplate LRA data or Code letter where available."

 

[aczlan]

On a 15KW PTO-generator the PTO speed is 540 but the gen set is runnng at over 3600 RPMs due to the gearing. At 540 RPM PTO speed my generator is kicking out 240 volts, at 60 cycles and is capable of producing 62.5 Amps

Correct (for a 2 pole generator head, a 4 pole head would only need to be spun at 1800RPMs), but I was talking about switching the tractor to use the 1000RPM PTO setting (if equipped) with a lower engine speed to power the generator at 540PTO RPMs. When you do that, you lose 50% of your PTO HP (+/- the difference in the torque curve between ~2600 engine RPMs and ~1300 engine RPMs.

Aaron Z

 

[Charlesaf3]

Couple pieces of exhaust pipe connected to the exhaust pipe of your tractor with a silicone hose should do the trick. Make sure to setup a remote kill switch outside the garage and a couple of CO2 meters in the garage...

Aaron Z

Yeah, I was thinking something like that. Only holding my breath - garage is small...

 

[Charlesaf3]

The trouble with that is the Xantrex for the truck is 12v. So let's say your house uses 2Kwh, that means 2k/12 = 166 amps draw from your battery and alternator. That's ok for small stuff like running a sander or lights on a job but your house most likely uses more than the 2Kwh I conservatively used in this example. For instance my off grid system is 48 to 72 volts nominal. (24v panels) Two 24v panels will run anywhere from 60 to 80 volts into the inverter, my other panels are a srting of 3 for 72 volts nominal or about 105 volts when the sun is running them. The higher the voltage the less copper wire for your runs. That's what you want, now back to the 48 volt battery bank that these panels charge. With the 2Kwh we used above: 2000/48 = 41 amps worth of copper. So to run an inverter from a battery bank you want at least 36 to 48 volts. So how do you charge that from your vehicle? Well, you'll need a special alternator and charging system. That's why your inverter system isn't the best. After you start putting appliances, etc. on the load end you won't be able to maintain them.

I agree, hence the 17kw hard piped natural gas generac - I think you missed that one above. Xantrex is just always available power - I can get 20 amps short use, say 8 amps constant at idle from it - alternator is rated 130, but I'm sure less at idle. Fine for job sites, might be able to run a fridge in an emergency

Oh, and I ran 0000 wire between the battery and the inverter, as specd by xantrex engineers. That was expensive...

If I need the full 20, I'll upgrade to the big alternator (350amp). I wonder if I can use the truck as a welder?

 

[Charlesaf3]

View attachment 287010

Someone asked about running the tractor inside with the door closed. This is a photo of my setup, since modified slightly for my current tractor. The exhaust is regular exhaust pipe from a muffler shop. I had them swage the end down to be a slip fit over the tractor exhaust. I have yet to need the generator in the winter so haven't actually run it like this beyond testing it out. The tractor generates a significant amount of heat when it is generating power. Last summer I had been away for a month, got home the night before the power went off for almost three days. I would run the generator in the morning for an hour or so to run the fridge and freezer, run the pump to have a shower and flush the toilet, make coffee then disconnect the generator so I could use the tractor to cut the grass and do other chores. I'd power the house again in the evening for an hour or so. That seemed to be enough to keep everything happy. I only have one tractor, seems like that is still enough. All told during the power outage I don't think I can atribute more than five hours run time to driving the generator so I'm not very worried about wearing out my tractor making electricity.

Thanks, nice idea, simple and sweet.

 

[Charlesaf3]

A PTO generator requires 2 hp at the pto for every kw...ie: a 15 kw generator requires 30 hp at the pto.

True of course. But you do get an advantage even if the generator is too big for the tractor, as I understand it - starting/surge amps and flywheel/inertia effect.

Which the well pump people should think about. That initial surge on motors matters

 

[Charlesaf3]

That's locked rotor amps! What happens when you lock a rotor on a motor? You blow the breaker! It's not the same as starting amps.

Motor Calculations | NEC content from Electrical Construction and Maintenance (EC and M) Magazine

" Motor locked-rotor current. If the rotating part of the motor winding becomes jammed so it can稚 rotate, no counter-electromotive force will be produced in the motor winding. This results in a decrease in conductor impedance to the point that it痴 effectively a short circuit. What痴 the result? The motor operates at locked-rotor current, often six times the full-load ampere rating, depending on the motor Code Letter rating [430.7(B)]. This will cause the motor winding to overheat and be destroyed if the current isn稚 quickly reduced or removed."

Electrical Motor Calculator

Plugging in 1 hp , 90% efficiency, 85 PF (power factor) and 230V to the calculator in this link.

You get:

1 phase = 4a.
FLA = 5A

What does FLA stand for? Full Load Amps! At full load the motor draws 5A, 230V * 5A = 1150W; 1 HP = 746W FLA for a 1 HP motor = 1150/746 or 1.54 times.

Now look at the chart for starting amps, what does the FLC state? 150% to 300% of running current and what's 300%? It's 3 times, exactly what I said. I work with this stuff everyday my systems are built on these calculations. Are you off the grid running several inverters on a daily basis?

While understandable, I'm afraid this is somewhat incorrect. A number of motors draw their locked rotor amps for a short time period at start up. Classic and common example is heat pumps. It's also true of some table saws, which has caused me joy over the years. My sawstop wired at 120 regularly trips the 20a breaker - surge is briefly 80 amps, per the engineers at the factory. Milliseconds, but still would stall out with a little 5k generator.

You can get around LRA with thoughtful staging of equipment starts - I have 3 HVAC units, and I bring them up big to small. But LRA is written on the plates for a reason (note, this is a purported advantage of inverter drive HVAC, no LRA issues)