MEP-831a Troubleshooting

[DieselAddict]

I'm working on putting together a 3kw load.

I did adjust the magnet. It was approx 1/8th turn. I can certainly put it back to where it was.

 

[Dewie38]

The problem is, the magnet has a certain pull off weight set by the factory (GAC), if you adjust that, then the rest of the set up procedure is no good.
The gap on the magnet is set to 1/4 inch when running at no load, that puts the actuator just outside the magnetic pull of the magnet, that should only be adjusted by the top swivel fitting on the actuator rod.

 

[DieselAddict]

OK. I can do that. The issue that was presenting is that the magnet would not hold onto the shoe when it was shutting down. It would hold it for a second but as the engine wound down and the pressure on the governor lever increased it would pop off leaving the engine running at a very low idle.

Since I have most of the other items resolved on the unit now I do want to make sure the governor and electronic controls are working correctly.

 

[Dewie38]

I the rod is not long enough then there is not enough mechanical pressure to hold the magnet.
The magnet is the stationary part of the actuator it is inside the cylinder that stays stationary, the part that moves we call the target.
The target moves away from the magnet when actuator is energized. The magnet and target should be 1/4 inch away from each other (target just outside the pull of the magnet) when running at no load, if you adjusted the magnet in or out of the cylinder then the magnetic pull the magnet has on the target will change, and the distance will be different.
Yes this adjustment will allow the set to shut down but will screw up the operation when set is running.

Does this make sense to you?

 

[DieselAddict]

It does.

If the specification for pulloff is listed somewhere I can make sure it is set to the correct value.

The governor was not running with that sized gap when I got it running originally. The gap was much larger than that.

Thanks for your info and patience.

 

[Dewie38]

You wont find that info anywhere it is factory set. I know this because I helped develop this set, and I wrote the procedure for setting this governing system.
To properly set the pull off weight you need to disconnect the actuator rod from the actuator, and you would need a pull scale to measure the weight.
The pull off weight is about 5 lbs.
If the original gap was larger than 1/4 inch then either the rod is not the right length or the magnet has been messed with already.
Or perhaps the set is not running at the proper no load speed of 3050 RPM.
In any case I will send you the procedure when I find it.

 

[DieselAddict]

Ok. Great. The info on RPM and pull will certainly get me started. I've done pulloff tests a number of times with magnets. I'm comfortable with doing that.

Thanks so much for the info.

 

[cdre]

I picked up a few of these in Albany a few weeks ago. I bought a pair of 16CL-B motorcycle batteries and put them in series for 24v. They barely squeeze into the plastic battery holder. Fit perfectly without the plastic in there. They kick over the starter with ease. They have the highest CCA I could find in a battery of that size (220).

I haven't had much time to troubleshoot it yet, but one that I fired up yesterday looks like it has governor problems as well. The "target" is much more to the right at rest than my other units. When running, it surges up and down dramatically with no load. When I push the switch to off, the target doesn't engage the magnet and the engine continues to run. I'll need to get in there and do some real troubleshooting later this week.

Dewie, if you can send me the governor adjustment procedure as well, that would be awesome. Thanks!

 

[DieselAddict]

Here is where I am now. The events here are the order I made the adjustments.

I set the magnet pulloff to a dead nuts 5lbs. It was a LOT less than that when I started. That was even after I had tweaked it for more hold. I measured the pulloff before the adjustment at about 3.25 lbs. It is a very sensitive adjustment. It took several tries to get it dialed in.

I'm using the load input to the speed controller to measure RPM since I can see the RAW generator output. 300hz is 3600. Low idle speed of 3050 is about 254hz.

I had to adjust the mechanical governor to get it down to 3600. It was set high by about 150 rpm. Its now a perfect 300hz on the nose.

I then set the rod length intentionally too long so it would reduce the RPM of the engine with a wider than normal gap. I did this so I wouldn't cause a bunch of stalls as I adjusted the RPM on the controller. I slowly dropped the RPM using the SPEED pot on the controller till I got to 254hz.

Once I had the low idle set correctly I adjusted the rod lenght so the gap between the target and the magnet was 0.25"

Right now its idling happily. I'm going to put my water heater load bank together now and see if I need to do any tuning on the controller.

Does that sound reasonable Dewie?

 

[DieselAddict]

I may have a bad speed controller. I had everything running well. It would take the load and drop down when the load dropped. Everything looked to be in order.

I was letting it run with no load and after about 20 minutes it went totally nuts. The throttle actuator just goes back and forth full power to zero and back. None of the adjustment pots does anything but change the period of the oscillation.

 

[Dewie38]

Diesel,
Sounds like you did good setting it up.
Where are the stability and gain pots set to?
They should be about 11:00 o'clock. That is, turn all the way ccw then turn cw to 11:00.
254 Hz is dead nuts no load speed and 288 Hz at full load.
I've been preparing for the blizzard we are having starting tomorrow so I apologize that I haven't had a chance to send out the setup procedure yet.
Sounds to me like you may have a bad controller
Try making the rod just a little longer and see if that helps

 

[DieselAddict]

Thanks. For a while it looked like I was about done. I'm going to try again later today and see if it has gotten its mind back.

I did try a number of things but here is what it's doing, the actuator will have a spazam about once a second and it wouldn't behave after that started. I could apply some pressure on the actuator with my finger to dampen the spazm and it didn't seem to upset the pid loop in the controller so I think there is a problem in the output driver circuit for the actuator.

The gain was at about 10 o'clock and the stability was at 9 o'clock. That was working well. I did have the boost pot set to let the rpm rise to 300 hz at full load since that is where the engine made max power. I can reset it to 288 if that is spec.

Where can I get a controller? I don't see them on the manufacturers website nor can I find them in a normal web search.

No need to apologize. Prep for that storm certainly comes first. Thanks for all the good info.

 

[R Racing]

Sounds like I'm going to have to buy me a paper manual for my mep-831A and a new O scope.

 

[DieselAddict]

I wasn't using a scope. I used the freq reading on the old fluke 87 meter. That worked fine.

Not that I want to deter you from buying a new toy though. I have a couple of them laying around here.

 

[DieselAddict]

Once I have mine fully working I plan to shoot a video on how to set the speed control up.

 

[R Racing]

Once I have mine fully working I plan to shoot a video on how to set the speed control up.

That would be great! !

 

[DieselAddict]

I found the detailed TM for the MEP831. The procedure to setup the governor starts on page 161.

I hope posting a link to the manual I stumbled across isn't against the rules.

http://www.liberatedmanuals.com/TM-9-6115-639-13-and-P.pdf

 

[DieselAddict]

I shot a short video with the cellphone to show the governor working correctly (I did warm it up for a few minutes before dropping the load on it). The battery in the phone died while I was recording the second video where it was acting up so that file was lost. I'll go out and shoot another one with the real video cameras. The gap between the magnet and the target is a little wider than spec but this is a close as I could get it without causing problems with the magnet capturing the target when the load was removed. I hope I can get a replacement governor module. That should finish up this project.

http://youtu.be/3mV9JZorGN0

 

[DieselAddict]

The batteries arrived today so I installed them in the generator. They fit the battery tray nicely. The overall dimensions are a little smaller than the single battery they replace. For the difference in cost its more than worth it. I think I'm going to turn them 90 degrees to where they are now and see if the cable come out neater. I tried to upload a photo but I received an error. I'll try again later.

I also got one response from the suppliers that provide parts for the military. They are willing to sell a single SLC100 for $650. Based on what I see other GAC controllers go for that is about 2.5x too high. For $650 I can build a controller that will manage the engine speed AND provide autostart/auto connect functionality. Unless I can find a replacement at a more affordable price I'll be ordering some PLC parts.

 

[Dewie38]

Diesel,
What supplier was that?
That's an awful lot for that controller.
I'm glad you got a copy of the TM, I was wrong on the gap, I said 1/4 inch when in fact it is 5/16 (been a while)
I've seen that condition before where the actuator catches, pops off, and then catches again, usually it is just a rod adjustment, that is if the magnet pull off weight is set properly.
I have several controllers but after viewing your video, your set sounds good.
Nice smooth increase in speed when load is applied and nice decrease in speed when load is dropped and no surge in speed or lag in speed when load is applied or removed.
Nice Job!