TC 40D PTO Generator - Disappointing

[djradz]

During this past ice-storm, I had plenty of opportunity to use my 13 kW PTO generator, with somewhat mixed and disappointing results. In the past I've powered the entire house including about 22,000 BTU of air conditioning, a freezer, 2 refrigerators, washer, electric drier, microwave, etc with pretty good results. This time, I had plenty of electric heat load (along with much of the aformentioned load, minus AC) and found both the voltage and frequency sagged significantly. The voltage I can see, as my cabling leaves a bit to be desired, and because the voltage is affected by the frequency drop, but the only way I can see the frequency dropping is due to the tractor not keeping up. Although the tractor didn't sound as if it was laboring, it must have dropped in RPM somewhat, for what else would cause the drop in frequency? Any thoughts? The generator (brushless-capacitor) does seem fairly sensitive to engine RPM changes, but I usually initially adjust the throttle to get 60 Hz under a mid-range load and then some things like the microwave, a couple of heaters, or washer/dryer, well pump come on and off.

I'm wondering if maybe the governor leaves a bit to be desired? I do recall that when mowing over many summers on some very hilly area of my property, that the tractor ground speed slows going up steep hills and speeds up coming down. I would have thought here too that the governor would have keep the engine speed and the ground speed constant (assuming no additional losses in the hydro tranny), but that is not what I seem to recall.

Anyway, back to the generator, or governor. Any ideas? Is the governor sensitivity adjustable?

 

[RickB]

If there is a significant use of electric resistance heat you may be underestimating the total amperage load; simply overloading the generator. Also, what is the age and condition of the tractor's fuel filter?

 

[schmism]

Anyway, back to the generator, or governor. Any ideas? Is the governor sensitivity adjustable?

im trying to imagine what a governor on a modern vehical looks like.....for a cruse control on a car its usually vacume driven...

(all i can think of is modern governor on a B&S were a spring pulls on a lever that controls the needle valve in the carb)

i wonder if it was the load type... restance (electic) heat load vs rotary phase load ie spinning compressor on the AC....

(my brain hurts but i want to say the diffrence is how much impedance is back fed into the system which WILL affect frequency/generator output) but all that is sketchy at best.....

 

[dynasim]

I wonder if gelling of the fuel was an issue? Also, did the tractor come up to operating temperature?

As I understand it, you said this same tractor setup worked in warmer weather. Can you confirm this, as I want to run a 10 KW generator using a TC45D, and was hoping that this worked.

Good Luck and Thanks

Chris

 

[dynasim]

Also, RickB pointed out to me that voltage and speed are strongly related on a generator, and therefore you voltage and frequency issues are likely related.

Chris

 

[Fredex]

First, when you say you set the speed, under moderate load, for 60HZ from the alternator, I assume either the alternator has a frequency (Hertz) meter or you have a test meter for that.
Then, here's is one way to test, assuming you don't pull full throttle to set up under moderate load. When the Hertz/volts sag under high electrical load, go the tractor and see how much the rpm has dropped, then pull more throttle. If rpm picks up readily your issue is probably governor sag. If it don't, you either have too much electrical load or aren't getting rated hp from the tractor.
TC40 should have 35hp at pto, 33 for HST models. That should be more than enough for 13KW. And yes, Hertz is purely rpm dependent, voltage change will not change hertz. However a load that causes tractor rpm to decrease will cause hertz to decrease and usually voltage also unless the alternator is very well regulated.
Fred

 

[Fredex]

Couple of additional thoughts. You didn't say how much the hertz was dropping with increased load.
Also some governor sag (sometimes called droop) is normal for the tractor. My tractor has high idle speed of 2300 which is calculated to give RATED speed of 2100 at RATED hp output.
Years ago I was responsible for emergency alternators in 4 microwave repeater stations; 2-71 and 4-71 Detroits spinning 30 & 60KW machines. THe loads we had for them were only one-third to one-half their capacity. However, we had to set them up for about 62 hertz at no load to end up with 60 hertz under the house load. And those diesels had governors designed for generator/alternator use.
I think it is 50-50 whether your alternator is overloaded or you are experiencing governor sag - or both. If it is sag, set it a little fast at moderate load and accept a little slow at max load - won't hurt anything unless you are talking way low hertz.
May be helpful to wrap a clamp-on ammeter around both legs of your 220-240 - See how many KVA you are really demanding.

 

[RickB]

Could also be as simple as inadequate tension on the throttle linkage friction disc. That would allow the throttle setting to 'creep' lower.

 

[SteveInMD]

I've heard that PTO generators often have trouble controlling voltage and frequency. That's why I went with a stand alone generator. A stand alone generator controls it own throttle to provide constant output.

 

[jinman]

I'm wondering if maybe the governor leaves a bit to be desired? I do recall that when mowing over many summers on some very hilly area of my property, that the tractor ground speed slows going up steep hills and speeds up coming down. I would have thought here too that the governor would have keep the engine speed and the ground speed constant (assuming no additional losses in the hydro tranny), but that is not what I seem to recall.

Anyway, back to the generator, or governor. Any ideas? Is the governor sensitivity adjustable?

Duane, I think you have plenty of good info on the generator end of your problem and the rpm/load/frequency relationships. I can only add some info regarding the engine governor.

As RickB noted, our throttles are notorious for "creep" and that is a possibility. The governor is not sensitivity adjustable. The only adjustment is a position when the governor is assembled. The throttle linkage is aligned to a slot before it is tightened onto a shaft.

The governor is a flyweight/cone affair and probably not very tight in its tolerance as you suspected. I could find no specifications on variance or error bandwidth. It might be as wide as plus/minus 50 rpm. That would take a loading test to actually get some concrete data.

Sorry I could not be of more help.