MEP831A - Overvoltage Fault

[DieselAddict]

I have an 831 that will give an overload fault upon startup if I leave it out in the rain. To resolve the issue I will let it run for 15 or 20 minutes. The heat from the engine will dry out the inverter. I can then cycle the power on the unit and it will run OK.

When I have some free time I'm going to pull the inverter and dry it out in the over then seal everything up. Hopefully that will stop the problem.

 

[CommieGIR]

So it works, but only if you are running the regulator in 120v mode, if you put it into 240v it drops voltage and has output issues.

 

[kloppk]

The inverter actually has two 120 volt inverters inside of it. In 240 mode it internally connects the two inverters in series and sets them them to be 180 degrees out of phase to generate the 240.
In 120 mode the two inverters inside are connected in parallel and are in phase with each other.
Sounds like one of the two inverters has an issue.
If you do open up the inverter you ought to look for anything abnormal such as the tops of the large black capacitors bulging or split open.
Also there are 4 small black fuses on the circuit board where P15 and P16 connect to the inverter. Those sometimes blow causing issues.

 

[CommieGIR]

Was planning to take the inverter out again anyways, so I'll look it over. I did check for bulging/burnt caps the first time, didn't see anything out of the ordinary without getting too deep.

 

[CommieGIR]

Hey KloppK,

So on the back of the inverter controller board, there's two connectors that come off going to the transformer/capacitor board and they look like they got a little hot. Any idea if that's normal?

 

[kloppk]

Not that I recall. Can you post a picture of the discoloration?

 

[CommieGIR]

Yup:

http://imgur.com/pXDA4bs

http://imgur.com/79cjQd2

 

[kloppk]

The second picture really shows the melted plastic housing. Must have gotten awfully hot. Never seen that before. Definitely not a good sign.

 

[CommieGIR]

Never is with electronics.

 

[CommieGIR]

So its reliably putting out 240v now, but still has the overvolt fault.

I've noticed when load drops off, it loses one leg until the engine revs back up with a new load. An odd issue, but it functions, will certainly not expect it to handle a full 3kw load.

 

[loosegravel]

So its reliably putting out 240v now, but still has the overvolt fault.

I've noticed when load drops off, it loses one leg until the engine revs back up with a new load. An odd issue, but it functions, will certainly not expect it to handle a full 3kw load.

More will be revealed! Good work so far.

 

[kloppk]

Did you check the 8 fuses while you had it apart? Those fuses are the input fuses for the two inverter power supplies. If any were blow an inverter wouldn't get the full AC power from the PMA.

The circuit board they are on also contain about a dozen high current diodes to rectify the 3 phase AC from the PMA to DC. Sometimes 1 or more of those diodes can blow messing up the rectification.

The large black caps are on the DC output to smooth the DC.

 

[CommieGIR]

I get the feeling this thing was in depot, a lot of the screws securing the coupling between the boards for the loads were loose. All the fuses you mentioned KloppK were intact and ohmed out good, so who knows.

But it functions as a generator, and that'll do.

 

[CommieGIR]

Hey KloppK - I'd be interested in the Aftermarket Gen Head kit if you have them.

 

[kloppk]

PM sent
Kurt

 

[loosegravel]

Hey KloppK - I'd be interested in the Aftermarket Gen Head kit if you have them.

It's very cool that people take the time to make aftermarket parts in an effort to keep these awesome MEP generators running isn't it?

 

[CommieGIR]

Very much, especially as most of the guts of the MEP are actually really well built...its the governor and power generation that is sketchy.

 

[CommieGIR]

Well that was short lived, now it starts and runs but then even with the Fault Controller disconnected its cutting power to the GC via K12, even though it appears to be showing good voltage out.

That Regulator/Converter really is the weakpoint in this thing.

 

[kloppk]

If its doing that its because K6, the Short Circuit fault relay inside the inverter is activating K12 killing power to the GC.

 

[CommieGIR]

I can only assume it got damp, which means pulling the inverter again.