802a power output issues

[Ray70]

The MOV is not seeing anywhere near 120V, if that's what you're thinking.....?

 

[Digger556]

Hey folks
I've got an 802a generator about 2500 hours
It has never given the rated power output. It is usually happy at about 2,000 watts. Anything above that and it surges.

It just started disconnecting power and the red overload light comes on. Only pulling 1600 watts of power. I have my inverters programmed to only take that much power and I can read how much is being pulled in real time.


Any thoughts what the issues might be?

You stated anything above 2000 watts causes surging. Surging usually implies the engine RPM (and gen freq) are hunting up and down, and unstable.

You also mention the overload light comes on. These are separate issues the way it's described.

Surging is usually a droop adjust or sticky governor issue with the engine. An overload light is an electrical issue.

If you can no longer reach a power level that induces surging, you need to fix the overload light issue first (typically dirty switch contacts), then address surging.

If the unit is wet stacked and can't reach full output, you still need to fix the overload light first.

 

[Ray70]

He's on it...
He's got the Deoxit on order so he can clean the switches, he's also working on learning about the droop adjustment and lastly he's going to address the potential wet stacking.
Now we sit back and wait for the results to come in....

 

[timberrrrrr]

I cleaned the am/vm and ac selector switches the best I could with Deoxit and excercised the switches lots. unfortunately the generator still goes into overload after about 15 minutes.

I can't really get into the guts of the switches or the slip rings on the back side. I can't figure out how the sliprings come apart. It seems there is a black keeper on both sides that should slide up to release the blue portion, but can't get it to work. Any recommendations how to get in for a more thorough cleaning?

 

[kloppk]

You want to spray the Deoxit in ALL the little opening in the switches by EACH terminal.
Here is a picture pointing out just two of the many openings on the switch's.
The left arrow is pointing to one of the exposed switch contacts in the switch. The switch's are not sealed.
After spraying them you want to exercise the switch's by repeatedly moving them through all their positions many times.
I'd suggest re-spraying and re-exercising them again.

 

[timberrrrrr]

The MOV is not seeing anywhere near 120V, if that's what you're thinking.....?

I wasn't sure what voltage it is seeing. I will order the 14d151k resistor, thank you

You want to spray the Deoxit in ALL the little opening in the switches by EACH terminal.
Here is a picture pointing out just two of the many openings on the switch's.
The left arrow is pointing to one of the exposed switch contacts in the switch. The switch's are not sealed.
After spraying them you want to exercise the switch's by repeatedly moving them through all their positions many times.
I'd suggest re-spraying and re-exercising them again.

View attachment 943458

Thank you for your reply
That is where I sprayed the Deoxit. Apparently you are right and I will get out there and spray some more and exercise the switches more as well

 

[timberrrrrr]

OK, I opened up the generator again this afternoon and thoroughly soaked all openings / terminals 4 times while working the switches over and over again probably 30 times each switch. I used most of the spray can of Deoxit

Fired up the generator, let it warm up for 10 minutes. Started with 1kw load for 20 minutes, then went to 2kw load. 10 to 15 minutes later the overload light was on and the green power light was off. Grrrrrrrrrrrrr

Thoughts?

 

[Light in the Dark]

 

[timberrrrrr]

Got it, thank you!

Gotta work today, wind came through and tore a couple of trees apart
Hope to get home with enough sunlight to check this out this evening

Stay tuned . . .

 

[kloppk]

Another way of narrowing it down without disconnecting any wires is to measure the AC Voltages going into the K8 Relay box. It's the input voltages that K8 uses to sense overload and short circuit faults.

Here's how K8 works. It's the same for all 3 of it's load sense inputs.
- An AC voltage into its load sense terminals ranges from 0 volts AC at 0% Load to 6.19 volts AC at 110% Load. K8 should not trip faults at all withing this range.
- An AC voltage into its load sense terminals of 7.5 volts AC represents 133% load. K8 should trip and overload fault in 8 +/- 2 minutes.
- An AC voltage into its load sense terminals greater than 7.5 volts AC but less than 23.9 volts AC represents and big overload. The higher the AC voltage the quicker K8 will trip an overload fault.
- An AC voltage into its load sense terminals 23.9 or more represent a short circuit and the K8 will immediately trip a short circuit fault.

So... I'd suggest measuring the AC voltage across K8 terminal pairs:
4 & 1
4 & 2
4 & 3
for the conditions above while you have your load applied.
If the AC voltages at K8's input pairs are all less than 6.19 volts AC and K8 trips a fault then K8 is bad.
If you find one or more AC voltages into K8 exceed 6.19 volts then there is an issue with the sensing wiring, burden resistors or S6 & S8 switches.

Here is a diagram of how the sensing circuitry is connect when in 120/240 Single Phase Mode.
How is works is... CT1, CT2, CT3 develop a current proportional the load on the gen head windings.
The current passing through burden resistors R10, R11, R12 & R13 from the CT's develop a voltage across them proportional the load.
K8 senses the developed voltages to sense for overloads and short circuit conditions.
A problem some have found is that when in 120/240 mode S8 fails to close connecting R13 in parallel with R12. When that happens the voltage into K8 from R12 is twice what is should be causing a false overload. This condition does NOT appear on the sts %Load meter.

 

[2Pbfeet]

@kloppk thanks! That was a nice explanation of how K8 functions.

All the best,

2Pbfeet

 

[timberrrrrr]

Thank you for all of your help, this is all excellent information.

Unfortunately it is raining pretty good here, will have to wait a day or two to start testing