MEP-805a floating or bouncing voltage

[Milhouse]

I have an MEP-805a, runs perfect, rpm doesen't vary much so it will hold at 60hz within .02, voltage will output a perfect 120/208, however it will drop or spike for a quick second every once and a while, its happens so quickly the voltage meter only moves slightly, I put on a volt meter with recording at 100ms to analize the range of drop or spike, and the 120V leg ranges from 102V-154V, the drops or spikes happen at randon, every 10-15 seconds or so, they are quick enough that simple motors like fridge etc. don't care, but I have a UPS that clicks on and off battery because it senses the error. Can also see it brighten and dim lights. Looked for loose connections, tightened every screw, its got me baffled, can't find a solution in the manuals. Anyone have any ideas? The unit also shuts down on occasion for overvoltage, or overspeed (even though it didn't break 60hz when it tripped overspeed)

 

[leedawg]

Im no expert however sure seems like its a voltage regulator issue. You should measure the field voltage coming out of the voltage regulator and see if you are seeing the same types of spikes. Should be a dc voltage. I know the older machines voltage regulator issues are pretty common don't know much about the Tactical quite sets though. Just acquired my first one and have not really started on it yet as a project. Another thing that could be done is you could put a dc voltage directly to the field and run the set for a bit say from a 12 v battery. Then measure the ac output and see if the spikes go away hypothetically without any changes in load and a constant source of dc voltage the field should stay consistent and thus produce an even amount of ac power without spikes.

Sorry I do not know the amount of dc voltage that the voltage regulator puts out off the top of my head but if you search around the forums you will see a lot of guys talk about this and get a good idea of how it works.

 

[glassk]

I have an MEP-805a, runs perfect, rpm doesen't vary much so it will hold at 60hz within .02, voltage will output a perfect 120/208, however it will drop or spike for a quick second every once and a while, its happens so quickly the voltage meter only moves slightly, I put on a volt meter with recording at 100ms to analize the range of drop or spike, and the 120V leg ranges from 102V-154V, the drops or spikes happen at randon, every 10-15 seconds or so, they are quick enough that simple motors like fridge etc. don't care, but I have a UPS that clicks on and off battery because it senses the error. Can also see it brighten and dim lights. Looked for loose connections, tightened every screw, its got me baffled, can't find a solution in the manuals. Anyone have any ideas? The unit also shuts down on occasion for overvoltage, or overspeed (even though it didn't break 60hz when it tripped overspeed)

Look in the TM for adjusting governor linkage arm,

4-15-4 Adjustment.
a. Tag and disconnect connector (1, FIGURE 4-7) from engine harness.
b. Remove nut(2) and disconnect rod assembly (5).
c. Manually move fuel injection pump lever to full fuel position.
d. Start generator set while holding fuel injection pump lever in position.
e. Slowly move fuel injection pump lever toward no fuel position until generator set shuts down.
Change 1 4





ARMY TM 9-6115-644-24


































FIGURE 4-8. Governor Actuator Assembly

4-28 Change 1

 

[leedawg]

Why would the governor be an issue if its holding 60hz within .02hz? Just curious sounds like his governor is working perfectly.

 

[1800 Diesel]

Why would the governor be an issue if its holding 60hz within .02hz? Just curious sounds like his governor is working perfectly.

I'm wondering the same thing--slight speed changes should not cause such wide spikes in voltage.

Still trying to learn all this stuff myself, but the VR seems to be a more likely place to look for trouble.

 

[Johny5]

Milhouse, Did you ever get this figured out? I am having the same issue with a MEP-803A.

 

[Guyfang]

Johny5,

Compleaty different system. The MEP-805 uses an elect gov and actuator system. If you need help, start a thread, and label it MEP-803 voltage problem. Or something like that.