Mep 003a voltage hunting

[Grega]

Last few times I fired up my Mep 003a, the volt meter has been fluctuating between 100 to 140 volts. The freq. guage is on 60 hertz but you can see it fluctuating slightly in sync with the volt meter. A couple times when I started the genny up, voltage was good untill I applied a load and thats when the voltage starts hunting again. But now it does it all the time. I shut the set down because I dont want to make things worse. So is my regulator board junk or is there something i can adjust. Ive had this generator for 6 months and it has been working good up untill a few weeks ago. Any help or an idea where to fix is would be really apprieciated. THANKS Greg

 

[Speddmon]

It is the voltage regulator causing the problem, but it is far from junk.

Start off by removing all of the wires one at a time and making sure they are clean and tight on the VR board.

Then if the problem persists, get out your -34 TM and follow the procedure for "Test, on Equipment" of the voltage regulator described in chapter 6-6 on page 6-8. The "Note" on that page says that instability of the voltage is most evident when a load is applied or removed. Just like your initial problem. The test and adjustment should take care of that problem for you.

Keep in mind that when the TM says to run it at rated load they are talking about rated load at 120v single phase configuration. I don't know how it would affect the adjustment if at all by running it at load in another configuration. I say this because finding 100 amps worth of 120 volt loads to run is kind of difficult at times.

 

[Grega]

Thanks Speddmon for the reply. I was looking over the regulator board last night and noticed that it was somewhat dusty. Will clean up the connections and maybe take a toothbrush to the board to clean it up. Will look the info in the TM also. As far as load I need to round up some portable heaters and get them wired so the generator will pull more of a load. The only load im applying now is from the 120 volt recepticle. By the way, still thinking about your spin on oil filter set up. It sure is a pain changing that canister oil filter.

 

[jbk]

theirs a pot adjustment on the a/c regulator board for voltage stability. i had voltage instalbility on a 002 i have and it did the same thing as yours, just not all the time and it turned out to be a cold soldered point on this pot. it would not mess up all the time. also be sure its not in the govenor, but since your hertz meter is staying at 60 i dont think its in the gov.

 

[Grega]

Update on my voltage problem. Printed the pages of TM showing "Testing the voltage regulator" When I turned the R15 pot screw, just a little, the generator started running fine, no more voltage fluctuation. Wonder if there was a little corrosion or dust inside the R15 pot causing the problem.

 

[Speddmon]

That very well could have been the problem. Even small "speed pots" that we use at work...if they sit with the wiper in the same spot for a long long time they start to act goofy. A lot of times we don't even change them, we just need to move them around a bit and they start working just fine again.

 

[Speddmon]

Anytime there are unsteady readings on one or more of the meters, check the ground wire underneath the control box. It is almost always the bad boy.

That's kind of a funny statement, I helped probably almost a hundred or more people on the forum with problems of various types on their generators, and that's never been the culprit. I'm not saying that it is not a source of problem or concern, but as a general rule that's usually not the problem.

 

[Grega]

Started the generator again tonight. Sitting right at 120 volts at 60 hertz. No fluctuation. Will work at getting some kind of load bank to test the gen. monthly, and as the instructions say for testing the regulator. There are some post about loading the genny, THANKS!!

 

[storeman]

my board has a screw adjustment on R16 but none on R15 unless I'm reading the board labels wrong.

Another (probably stupid) concern, is it safe to be adjusting that board with the generator running?

Jerry

 

[Keith_J]

No, it isn't safe with the panel open BUT if you must, use insulated tools and rubber gloves. 120 volts is present on a few terminals.

As to load testing, you can do it at 2 and 3 wire single phase as well as 3 phase 4 wire connections. The field lighting sets are good for this, if you can find them. But with 100 watt 120 volt bulbs, you would need 100. Better would be an old electric range with the set in 3 wire, 240 volt output.

Always test with resistive loads, using a motor as a load will have a variable power factor.

There are 6 field windings, each produces 120 volts. The reconnection switch dictates how each field coil is connected to the load.

 

[Grega]

An update on my voltage not being stable, bouncing between 100 and 140 volts. I tried adjusting the R16, not the R15 as I said in a earlier post. The R16 is the right one. It worked for awhile but now its doing the same thing again, bouncing between 100 and 140 volts. Govener arm moves slightly but when I hold it still, the voltage is still crazy. Adjusting the R16 while running 3 1500 watt heaters doesnt help either. Called a couple electronic places, they dont want to look at the voltage board. So a few days ago, I ordered a new VR board from DELKS. It should be here in a couple days and will give everyone an update on my problem.

 

[Keith_J]

There are plans to make a voltage regulator test unit in the -34. But if you have a new VR source, that might be cheaper, if not easier.

 

[AceHigh]

While on this subject, I was load testing the 003 at home for the first time today and as the loads increase or decrease (water heater on or off, well pump on or off) it will go to 58.9 hz or 61 hz. I can adjust it to get it right on 60, but it will vary that much. Is that normal or not? Thanks.

 

[glcaines]

The frequency of my MEP-003A will vary slightly like yours when big loads come on and off line. It is normally not a big issue. As far as load testing goes, I simply throw the transfer switch, which is manual and supplies the entire house, and turn on all the lights, both ovens, all cook top burners, two portable heaters and the HW heater.

 

[Keith_J]

Frequency is dependent on the RPM of the engine which is dependent on the governor and engine reacting to the increased torque from varying demands.

Being purely mechanical control system, it balances centrifugal force against a spring force, much like any mechanical injection diesel. Put a greater electrical load, RPM drops and the spring now has more force than the centrifugal flyweights. This allows the injection pump to inject greater volumes of diesel, meaning more cylinder pressure for longer duration which means the engine is producing more torque. If the RPM increases, centrifugal force exceeds the spring force, causing less fuel to be injected.

Such control systems are worthy of graduate degrees in mechanical engineering...not going to go that deep in this post. But two conditions of control exist, droop or frequency lag and overshoot. Ideally, the governor should have minimal overshoot, settling at 60 Hz (1800 RPM) after a sudden load is applied. The huge flywheel effect of the rotor helps here but also fights recovery of the engine.

IIRC, the -34 has instructions on setting the governor to minimize droop and overshoot.

 

[Grega]

Recieved the new regulator board from Delks surplus and installed it last night. Started the generator up and voltage went to 120 and stayed steady. So something on the old regulator board must have been the problem. The new board was dated 1997 and it looked like it better quality than the one I removed that was dated 1985. Better soldering and updated componets. I will some more checking around to see if anyone can fix my old VR board, there arent may places that fix anything electronic. because everything is throw away now days.

 

[Keith_J]

Take a good picture of the old board. I might be able to repair the old one.

 

[Grega]

Will get some pics up tonight or tomorrow. The old board was tan in color and the new one is green. Do you have an idea what usually goes wrong with them. Ive read the the capicators dry up but not for sure if thats true or not.

 

[Keith_J]

Capacitors can dry up or more commonly, bulge. Either way, they lose capacity . Really, think of them as surge chambers. Piece of cake to replace all, it takes too long to test each one.

Other things are pots burning the wiper contact area. Also easy to test.

But testing the entire unit may be difficult. I don't have cross-reference on the -24Ps between the 002a and 003a so I would have to borrow a genset if they aren't the same.

I think I could sweet-talk mk into loaning his. Takes too much time to make a test bench for a one-off.

 

[Grega]

Here are some pics. The new board is installed in the background. Also included is the generator that I just mounted on a trailer that my brother made.