Generator Not Maintaining Correct Speed for Load

Since the electric loads are the same for both generators and the ailing generator displayed normal electric load condition but a below normal frequency display that agreed with the sound of a slow engine, I suspect that you have a problem with the engine and not the generator.

Did you contact the manufacturer (Caterpillar?) or any mechanic?

Yes. Am waiting to hear back from them. While looking things over again. noticed that my actuator may have been limiting out. i readjusted the linkage between the fuel rack and actuator. Not sure if this was the problem, but everthing seems to work again.

Before, i wasnt seeing any voltage on the switchboard. normally at idle, i see around 290V. but was getting nothing before. now everything seems to work. I still dont know if i trust it enough to but back on line by itself.

It sounds like you've something else going on, unless someone snuck in and adjusted the actuator linkage while you had your back turned. Are you sure that the governor is handling the load on the engine? For you to adjust the actuator linkage and it seems to fix it, leads me to think that the governor isn't doing it's thing by increasing the throttle.

The actuator had been changed out about a week ago. So i was thinking that it wasn't positioned right. hadn't run that engine under much load since then

Why was the actuator changed out? Do you have any means of load testing the gen-set?

Allow me to suggest a stab in the dark. The adjustment on the fuel rack actuator may have just vibrated loose over time. Until the vibrations moved the adjustment far enough that the mechanical control could not compensate for the movement the effect of this adjustment loss was not noticed.

If the gensets can now be paralleled successfully, you could back off on the other generator and see how well the repaired one picks up and holds the loads. If it maintains speed, voltage, and kw, it looks good to go.

(Earlier I wondered about fouled injectors, which could happen while still having normal fuel pump pressure. The further info made that seem unlikely.)

After re positioning the actuator linkage, it seems to be fine now. i put it online by itself, and maintained like normal. i still feel there was something else going on for none of the meters to be showing anything.

the actuator was originally replaced trying to troubleshoot a previous problem, but was found not to be the problem. it was a 12v ground to the load sharing switch, causing that gen to want to always share load.

the generator itself still makes me suspicious. it was installed early July and was kind of rushed in. i was not here for that, but still think its something to do with it, i have never had these kind of problems with my generators until this one was put onboard

Thank you for all the comments and suggestions though......

Well, sooner or later, preferably with an engine tech present you will have turn the set on. Since it is a frequency problem, load is not needed at first.

There is a recurring remark that bothers me. You say, that then and then the meters show nothing (abnormal, or what??) outside the low freq??

for the voltage meter to show nothing at idle, is abnormal. normally around 290V. when engine is at rated speed, normal readings are 480V, 60Hz

Please let me know the rated speed and voltage.

rated speed is 1800rpm, and voltage is 480. control voltage to the acutator is 24vdc

Your sync instrumentation does not usually show anything before you are at about 58Hz so that may account for the no show.

The cause for the sudden change in speed would make me suspicious of the original fault not being fixed, but due to an intermittent short somewhere. The generator wanting to share load lowers speed due to droop and having no other machine to share with it just drops the frequency..... but dropping to 55Hz seems to be way too much, larger machines would be destroyed by that. Can your frequency meter even read down to 55Hz?

55Hz is the bottom of the range on my meter. when i was observing the problem, i could notice the meter kind of surging between 55Hz and up to about 58Hz.

If the problem seems to have gone away for the moment you could try and run the machine in parallel with another one, sharing the load 50/50. Then start a large pump and see how they share the increase, this should give you some idea of how well the governor is responding. I am thinking the governor bushing may be sticking sometimes and not responding to load changes when stuck.

You could also try to disconnect the governor and the linkage and move the linkage by hand (with the machine stopped, of course) to ensure there is no sticking in the movements

This was my same thoughts in my post #3, sounded like the governor wasn't responding to the load increase.