PTO Generators, been here before?

[4570Man]

I have digital readout on the tractor that tells me the pto speed.

 

[Sawyer Rob]

Your tach has the pto speed marked on it, and the pto gen set has a meter, for fine tuning that speed, to get the proper voltage...

SR

 

[aczlan]

Does anyone have an inexpensive easy to use tool to measure PTO speed?
I'm thinking like a little IR gun you point at a marker you put on the shaft and it tells you rpm.

Here is one: Digital Photo Sensor Tachometer

Aaron Z

 

[Gary Fowler]

Does anyone have an inexpensive easy to use tool to measure PTO speed?
I'm thinking like a little IR gun you point at a marker you put on the shaft and it tells you rpm.

PTO speed is not what you are looking for. You want the PTO to spin the generator at the rpm needed to produce 60 Hz. PTO speed is really irrelevant to the speed actually needed for clean generator power.
Invest in a meter to tell when you are producing 60Hz electrical power and set your throttle to that speed.

 

[Fallon]

PTO speed is not what you are looking for. You want the PTO to spin the generator at the rpm needed to produce 60 Hz. PTO speed is really irrelevant to the speed actually needed for clean generator power.
Invest in a meter to tell when you are producing 60Hz electrical power and set your throttle to that speed.

Generator manufacturers understand that, so they make the gearboxes to that 540 RPM input = proper speed for 60hz output.

 

[wrooster]

wrooster that was an interesting read. Having the dual generator setup was a definite plus when it came to fuel consumption.

Yes, that is the intent. As long as you are comfortable "house camping" with limited power for the majority of the time, it's a good setup. As I wrote, my overall fuel consumption was a mere fraction of the folks using 5 to 7.5KW generators. The unavailability of gas for a week or so made using such fuel-hogging gas units really cumbersome, so having a tiny inverter generator was really handy. Using the PTO generator for just a half hour or so per day made it possible to use all the "big stuff" (deep well pump, and ultimately the washer and dryer) with minimum fuel consumption.

wrooster

 

[wrooster]

Generator manufacturers understand that, so they make the gearboxes to that 540 RPM input = proper speed for 60hz output.

As noted by several folks above, in practice you don't really care what the exact PTO speed is. You simply "tune" the tractor throttle setpoint until the output frequency is nominally 60Hz (it may vary from about 58 to 62Hz depending on load). Most all PTO generators incorporate either a digital frequency gauge or a simple set of "idiot lights" that help determine whether you are too low or high in engine RPM.

Every PTO generator will consist of the alternator head itself mated to an up-conversion gearset. The nominal 540RPM input to the gearset will result in either 1800RPM output (for use with a 4 pole alternator head) or 3600RPM output (for use with a 2 pole alternator heard). There are advantages and disadvantages with both alternator head types, but in general a 3600RPM/2 pole head will have somewhat greater transient (surge) capability due to the faster rotating mass.

In the second picture below, note the black cast iron assembly between the PTO coupler guard (on left) and the alternator head (on right). That assembly houses the up-conversion gearset, bathed in oil. There is a fill plug on top for 90wt gear oil.

wrooster

 

[Fallon]

A Kill A Watt is only $20-30 or so & among other things it will measure Hz. Its not easy to see at distance & not rated for outdoor use. The P4400 is the origonal one & does Hz at least, not sure for other variants.

If there were a better weatherproof meter at a reasonable price I might consider it for my generator as it is an older unit with just a voltage range indicator not any frequency type gauge. My Kill A Watt will get the job done for now. Anybody know of any? I Googled a bit a while back, but couldnt find anything.

 

[newbury]

Here is one: Digital Photo Sensor Tachometer

Aaron Z

Thanks Aaron.

And I know about the built in measuring devices but I don't trust them without verification. Especially if they are digital.

 

[Sawyer Rob]

Thanks Aaron.

And I know about the built in measuring devices but I don't trust them without verification. Especially if they are digital.

Well, measuring the RPM won't help you any, you need to measure the electrical output of the generator NOT what the RPM of the tractor PTO is...

SR