Generator 15KW PTO Generator Harbor Freight

[Reg]

I agree with Treemonkey. I would be interested in a PTO unit like that.

We have an old 1992 Kolher 5000 watt generator in the MH and its voltage and Hz output are not a direct function of RPM's of the engine but are set by solid state devices that are adjusted with a screw driver.

Its no load output was 118 volts and when I reset it to 126 volts (factory spec) I was able to run a lot more things before brown out condition occured.

I still think the frequency variation (or lack of variation) is much more a function of the tractor's governor than the generator itself.
The load is the load is the load, etc., how well the tractor keeps up with the changes in that load, whether increasing or decreasing, determines the consistency of the frequency.
A sufficiently large flywheel (doesn't have to be "large", just has to have a lot of moi, i.e. mass at the rim) can probably help ride through motor start peaks.

 

[Soundguy]

any ideas how many poles and what kind of gearbox ratio.. that will make a difference as well.

a 6:1 gearbox for a 3600rpm head is going to react differently ( frequency wise ) to a pto speed fluctuation, than an 1800rpm head.. etc.

soundguy

 

[SPYDERLK]

I still think the frequency variation (or lack of variation) is much more a function of the tractor's governor than the generator itself.
The load is the load is the load, etc., how well the tractor keeps up with the changes in that load, whether increasing or decreasing, determines the consistency of the frequency.
[A sufficiently large flywheel (doesn't have to be "large", just has to have a lot of moi, i.e. mass at the rim) can probably help ride through motor start peaks.]

That is a good method for motor starting with a large gen driven by an undersized engine. The flywheel has to store a lot of energy to be an effective buffer for minimal slowdown during the proportionally huge startup load. This dictates that the flywheel be designed properly, as you say, with major mass and adequate tensive restraint at the rim. Also, if it is not large it has to be spinning very fast. Large is better so it can just spin at engine speed and avoid parasitic gearing losses. Also, spinning the flywheel in air wastes some power constantly so it shouldnt have spokes or similar irregularities.
larry

 

[SPYDERLK]

any ideas how many poles and what kind of gearbox ratio.. that will make a difference as well.

a 6:1 gearbox for a 3600rpm head is going to react differently ( frequency wise ) to a pto speed fluctuation, than an 1800rpm head.. etc.

soundguy

The only effect there would be the higher efficiency of the 3:1 gearbox on the 1800 gen. The proportion speed change of the gens would be the same as eng speed changed, so, in that way they should react the same.
larry

 

[Gale Hawkins]

Yes to the question of needing 2 HP at PTO for every 1K watt of out put so a 20K continueous run PTO generator would require a 40 HP tractor however a 20 HP (at the PTO) tractor could produce 10K watt of output with that generator. Over buying just cost more in weight and money.

Our Kohler voltage and frequency are adjusted with electronics and the normally expected engine speed. Now if the RPM dropped from 1800 to say 900 then the electronics are not going to be able to compensate for that kind of RPM change.

 

[Reg]

any ideas how many poles and what kind of gearbox ratio.. that will make a difference as well.

a 6:1 gearbox for a 3600rpm head is going to react differently ( frequency wise ) to a pto speed fluctuation, than an 1800rpm head.. etc.

soundguy

Good point.
I still don't have a unit, so can't get to specs for it.
For the trick I am considering I guess the question becomes how well the governor tracks at nominal engine speed for 540 PTO vs how well it tracks at 54% of that.

SOMEWHERE there is some data on marine diesels operated at 60% of their peak HP, which seemed to be optimum for fuel efficiency (consumption per output HP).

 

[Gale Hawkins]

When I had my Zetor with the 540/1000 RPM PTO I had considered a PTO generator and run it on the 1000 shaft when demands were low since that 45 HP tractor burned less than a gallon an hour bushhogging. That would have required buying the second PTO shaft for the 1000 rpm splines. Turning the 1000 shaft at 540 RPM would have put the engine in it high torque band. Even it it was only producing 20 HP that would have given me 10K watts of power. A slow turning diesel engine is not going going to drop the RPMs as fast as a 20 HP gas engine when hit with a surge load I would thing meaning you could start motors better than with a 10K watt home generator.

I have looked at low price older low hour power plants (15+KW) on ebay on the cheap. While that is VERY attractive full time set up you still another old engine to keep ready to start. The typical tractor is going to be ready to start when the power goes out. If you have prewired for a PTO set up you should only be talking 5-15 minutes to having back up power on line.

Health is the BIG negative to using a PTO set up. I can see myself with a new hip, knee the week before trying to look up and climb on the tractor to put a PTO based generator on line.

 

[Soundguy]

The only effect there would be the higher efficiency of the 3:1 gearbox on the 1800 gen. The proportion speed change of the gens would be the same as eng speed changed, so, in that way they should react the same.
larry

that's my point. the higher efficiencey unit would see less gearing loss.

soundguy

 

[Soundguy]

Health is the BIG negative to using a PTO set up. I can see myself with a new hip, knee the week before trying to look up and climb on the tractor to put a PTO based generator on line.

mount the pto gen to something like a pallate fork or carryall, then it will be easy to hitch to the tractor... could even use onne of those easy hitches.. just back up, and lift and click.. then attach pto shaft.

soundguy

 

[Reg]

Yes to the question of needing 2 HP at PTO for every 1K watt of out put so a 20K continueous run PTO generator would require a 40 HP tractor however a 20 HP (at the PTO) tractor could produce 10K watt of output with that generator. Over buying just cost more in weight and money.

Our Kohler voltage and frequency are adjusted with electronics and the normally expected engine speed. Now if the RPM dropped from 1800 to say 900 then the electronics are not going to be able to compensate for that kind of RPM change.

That is the bit I have a hard time understanding - HOW it adjusts frequency "with electronics".

I doubt that it is an inverter design, i.e. an AC generator rectified to DC which powers an oscillator to produce exact frequency AC, although those are available and very nice, since they idle down to a very slow standby and only rev up enough to supply sufficient power, all the while putting out the same voltage and frequency.

MOST AC gens put out a frequency that is directly proportional to shaft speed.
So is it AC -> DC -> AC ?
or is it just an electronic speed sensor feeding back to the engine's carb or fi system ?