Can anyone help? MEP-017A

[rexydg]

Hi folks, got a problem here, my MEP-017A decided to die.. I was running it under load and my lights got real dim. then started to fluctuate up and down. finally there was no power reading at any of the gauges on the generator side of the panel. i tore into it, just because I knew there were a few things that needed done, the bearing was screaming and a good cleaning wouldnt hurt it either. Here is my problem. As a mechanic, I am great.. I can have the engine torn down and rebuilt in 3 hrs, I am an aircraft mechanic so im no stranger to that half of a cessna 150 engine on my generator. the problem is that I dont know jack about the generator itself or the electronics contained in the control panel. I am looking for a TM right now, and once I have it im sure i will be able to understand most of it. I was just wondering if anyone out there had any suggestions on what might have caused this failure, is there a common problem that these gensets encounter.. maybe just relays or something, coils?, windings? I am at a loss, and every generator shop around here is afraid to touch it, and tells me that they dont have any idea what these parts do. does anyone have any suggestions? I really dont want to have to scrap this critter it has served me well up until now. any suggestions would be greatly apreciated. thanks.

[B.Sparks]

I suspect your problem is to be found within the switch that selects the output voltage and phase configuration. This switch is found inside the control box. With the engine off, rotate the switch through it's different positions. It should close at each one with a definite 'snap.'

Your machine is 30 or more years old and has probably not been stored under the best of conditions. The selector switch can become sticky and corroded. It has lots of contacts and handles the full output current. If the switch needs attention, do not spray it full of WD-40! Try "real" contact cleaner. Also, do not attack the contacts with sandpaper or emery cloth. Believe it or not a dollar bill make a great contact burnishing tool!

I once took one of those selector switches apart. Polished each contact as well as lubed the moving parts. What a job..

[rexydg]

thanks for the response.. the switch seems to be ok.. it clicks into position hard and definite. im kind of suspecting the voltage regulator, is it possible that it would fail in a way as to produce no power? it has onan part # 305D316 on it and im trying to find out if there is a civilian "counterpart" that may replace it. although there very well may be other issues. I hope I dont have to pull that main switch it has a gazillion wires on it as you well know.is there a method of using a meter to test continuity through it in different positions, and once I recieve my TM will it have detailed troubleshooting techniques in it? looks as though im going to have to get to the bottom of this problem since there are no shops within 300 miles that are not afraid to touch it.

[B.Sparks]

I'd still suspect the switch. Anyway, is your voltage regulator (V.R.)connected by means of screw terminals or with a big plug? If it has screw terminals you might try disconnecting the field wires (F+ and F-) from the V.R. and power them with an outside source of DC, such as a 12 volt battery.

If the V.R. is at fault, you'll see at least some voltage generated when the field is seperately excited. The regulator can be tested with a small light bulb and a variac. (I've repaired a number of V.R. units) If it would help I could look up the terminal numbers for you.

Another possible source of trouble is the exciter diodes. These are mounted on the generator shaft and rotate with it. I've seen these get stressed by centrifugal force. Eventually one of the leads breaks. Usually when this happens the gen operates but doesn't put out full voltage.

[B.Sparks]

OOPS, forgot something. One way to quick test the switch is to set it for a voltage other than what you are using now. For example, if you have it set up for 120 VAC, single phase, you might try setting it to 208 VAC, 3 phase. This will make and break different contact sets. Then check all 3 phases. If you see any difference, even if only one of the 3 phases starts to work, it would point to a switch problem. If the unit is still dead, look elsewhere.

[rexydg]

I have the generator apart right now, I pulled it apart to change the bearing out it was squealing, also to clean out all of the accumulated dust and dirt. I went and got some electrical contact cleaner and tried to spray it all inside of the switch, dont know how much actually made it in there. when it did go down that was one of the first things that I did do was to move the switch to another setting but I didnt change or check any of the lugs for power i was just looking at the voltmeter. it didnt move. I cleaned it up good and looked for any leads or wires that may have broken off inside and didnt see any. As far as the VR goes, I know where it is in the unit but not how it operates, it has 6 wires going to it and they are screwed down onto terminals. I believe the exciter diodes you are referring to are on the part that rotates.. dont know the name of it .. but there are 3 of them and all of the leads are very solidly attached. and the last one goes down through the center and is attached to the coil in the center. the bearing is supposed to arrive tomorrow, and the TM will be here in a few days. once the bearing shows up I will put it back together. once I get the generator back together how do I test it via the cannon plug to make sure that it is generating the proper power? I want to be able to eliminate that part of it from the troubleshooting so that I can concentrate on what else it might be. and what do you charge to rebuild control panels..LOL.

[B.Sparks]

I don't know why anybody who's familiar with gensets would be afraid of the milsurp units. These sets, although complex, are not all that hard to work on. They're well made and the schematics are usually right on the unit itself. Finding your problem just a matter of using some straight-forward troubleshooting techniques.

Once you get your set running again, I suggest you try seperately exciting it. This will help determine if your voltage regulator is faulty. Look on the voltage regulator for terminals #20 and #21. Remove the wires from the reg. and apply 12 VDC to them. (+ to the wire that was on term. 20, and - to the wire that was on term. 21) If the gen puts out power, the regulator is suspect.

[rexydg]

OK heres what Ive got.. I put this critter all back together, new bearings roled it over by hand, everything was good. started the engine runs like a champ. there still was nothing showing on the voltmeter. I opened the panel and there is a TOGGLE switch inside the panel that says "MANUAL FIELD FLASH" when I move that switch to the "flash" position the volt meter moves a few volts upward, if I do it again it moves more, after 4 flashes the voltage and cycles are where they are supposed to be. it then puts out voltage and I can run my lights, electric stove, water heater, fridge, TV, microwave, everything I want to at the same time and it does not falter. Now when I turn on my A/C unit it will not start it. When I got the genset it had no problem starting my A/C and running it. it barely hiccuped when it started it. now it doesnt seem to be able to produce that surge to kick it off. and I have to manually flash that field.. which field that is I dont know. I was hoping that this would be enough information that you might be able to offer a diagnosis or at least narrow it down to a single problem.. What do you think? You definitely have more knowledge in this arena than I do.

[rexydg]

I forgot to tell you.. on the VR there are 6 terminals with wires on them, they are numbered 1-6 from left to right I didnt see a 20 or 21 I added some pics here so that you can see what im refferring to. thanks

[rexydg]

heres the switch

[rexydg]

try this again pic was too large..ok

[Jim McIntyre]

Originally Posted by rexydg

it then puts out voltage and I can run my lights, electric stove, water heater, fridge, TV, microwave, everything I want to at the same time and it does not falter.

All this at once? That's a 5kW genset. An electric stove and water heater could easily pull more than that. How do you have this wired in to your house? What position is the voltage selector switch set to?

So, the set runs fine, puts out the proper voltage, but you now have to flash it? I'd suspect the field wires are reversed. In any case, it won't hurt it to swap them and see if that problem clears up.

Oh, and what size/voltage is your A/C unit?

[Wayne 440]

If a "good" MEP-017 will run all that at one time, I'm going to buy two, and some good hearing protection. My water heater alone is 4500w.

[rexydg]

The A/C says 22.7 amps@208/230 volts, as far as the other stuff it does run it all I swear fellas...my microwave makes the rpm drop a bit as well, as when I turn on more than 2 burners on my electric stove, I have the switch set on 208- 3 phase and have it wired into my panel. the genset always started my A/C with no problem, my home is only 1800 sf so its not a large unit. but it always started it fast b4 I ran into these problems. like I said once I flash it and get the voltage up it will run everything BUT the A/C today I turned on all my interior lights ran my 120v well pump, kicked on my water heater, plus tv and ran my small microwave for 15 min. and it only started to slow down after I turned on the second burner on my stove. These units will put out significantly more than 5 kw, and I am only 17 feet above sea level here also. Which I think helps. as far as wires being reversed... none have been removed.. they are in the same places as they were when I got the genset.
and if you know gensets better than I do , Yes I would reccomend you get some of these, just add the extra pipe and car muffler, and you can forgo the hearing protection.

[Jim Rankin]

Starting a motor is different from most of the other loads you mentioned. When starting a motor, amps are very high, but the actual engine load is not that much greater because the power factor is so low. Most of the current flowing to the motor at the very beginning is reactive power and that depends on excitation and generator end capacity.

I would suspect some diodes are shot somewhere, fuse blown or there is a short in some transformer somewhere which is cutting the kVAR the set can produce. This also would keep it from self exciting most likely.

time to get out the old multimeter and trace it all out. First candidates are the rotating diodes. They conduct electricity in only one direction. If they don't conduct or conduct both ways they're bad. On the armature the diodes are in pairs a positive and a negative and several of the same type may be attached to the same heatsink. If they can be unscrewed, that would be easier, but they must be isolated somehow to check each one separately.

Jim

[Jim McIntyre]

22.7A - that sounds like a 3 ton unit. I have worked with these mil gensets a lot, and yes, they are conservatively rated, but there's no way I'd recommend using a MEP 017 with a 3T A/C unit. Could it work? Sure. Would I want to rely on it? No.

These sets rely on whatever residual magnetism remains in the field to self-excite. If that magnetic polarity is reversed from what the voltage regulator is trying to establish, you'll have to flash it. After you run it a few times, the problem may go away. Or swap the field wires (5 and 6) and see if that helps - only takes a minute.

If that doesn't help, I'd agree with Jim R - could be a bad rotating diode - that might explain the intermittent problem you noted in your first post.

How bad was the bearing? Not bad enough to let the rotor rub against the stator laminations, I hope...

[rexydg]

I imagine that thats about right a 3 ton unit that is. like I said when I got it it had no trouble at all starting the unit, it would fire right off. the 5 and 6 terminals you ar referring to, are those the number 5 and 6 that are on the VR that I have pictured? I did not get my TM yet, although I do have one on the way. the bearing was in bad shape for a bearing, it wasnt at the point of catastrophic failure or anything it had some end shake and the seals were dried out and cracked up, it was just rusty inside from lousy storage and it had a squeal while it was running. I looked at the rotating portion of the generator when I took it off inspected it thoroughly and there were no areas that I saw where anything had rubbed or where the wires on the winding had lost any laquer or anything like that. it did have some surface rust on it, I cleaned that off and sprayed it with a light clear coat to prevent any furthur rust. these diode you are referring to I assume are the ones mounted on the rotating portion, there are 3 of them from what I could see, does that sound right? I would just like to have it work the way it did when I got it. It can be pretty miserable here in the middle of sep. after a hurricane with no A/C. Like i said it had absolutely no problem starting that unit before. do you think that maybe that is what caused things to go bad? If so I may have to invest in a 120 window unit for 1 room and use that instead. Like Ive said before, I am not an expert on these machines by any stretch of the imagination. but I did know that for the money I wasnt going to find a tougher genset, and after the hurricanes here we are without power for 7-9 weeks at times. the regular gensets that you can buy for 1800-2000 dollars all burn up fast. my neighbors had them and were sorely dissapointed with them after a week of running most were dead. I ended up housing one neighbors supply of insulin for his daughter because theirs stopped working, and filled my fridge and freezer with their food and others had the same problem. mine kept plugging away, keep in mind that I dont run it 24-7 either 3hrs morning again about 2pm, and then 4 or so hrs to cool the house down before bed. it would just be nice to have the same thing I had b4.

[B.Sparks]

We have a handful of MEP-017A's here at work. All of them were retrofitted by Uncle Sam with electronic voltage regulators back in the 1980's. Your set still has its original electromechanical 1960's vintage regulator. (That's why your reg. doesn't have terminals 20 and 21.) Rusty as it is, your regulator might be a bit flakey. It's simple to retrofit the electronic regulator, but these things are a bit expensive. It's also possible to install a 'civillian' regulator, if you can find one. The field flash switch (which I totally forgot about) applies battery power to the generator field.

There are 6 diodes mounted on the rotating ring. If any of these things go bad your set will not produce full voltage. If it comes up to voltage, even if only briefly and/or at no-load, chances are the diodes are good. They either work or they don't work.

I've load tested a few of those units and they are good for a continuous 7.5 kW. (resistive load bank) The voltage stays right where it was set and the frequency hangs in at 58 hZ. That's excellent performance - try a 50% overload with a typical commercial genset and see what you get for voltage and frequency regulation! As you push towards 8 kW, the throttle is wide open but the engine starts to slow down.

What happens to your set under load? Does the voltage drop? How about the frequency? A drop in frequency indicates that the engine doesn't have enough muscle for the job. If that's the case you might take a look at the carburator, specificially the linkage. There is an adjustable throttle stop. Be sure this isn't keeping the governor from opening the throttle all the way. When your engine is off, look at the linkage. The throttle should be almost fully open. The throttle stop is there so that the governor doesn't continuously "mash" the throttle open, possibly getting stuck there. Properly set, it should allow the throttle to be held *almost* wide open yet not let the governor spring tension try to push the throttle plate past open.

[Jim McIntyre]

Originally Posted by rexydg

If so I may have to invest in a 120 window unit for 1 room and use that instead.

I think that's a great idea. This set is really not big enough to reliably run a 3T A/C unit. (or find the 10 kW big brother to your MEP 017)

My gut feel is that your genset is fine. If it can supply the rated 208 V to your water heater and a few stove elements, it's in pretty good shape.

Your regulator is electromagnetic - nothing mechanical about it. They are very reliable. Could be, though that a newer electronic regulator would improve the genset's surge ability, but it'd an expensive experiment...

Yes, terminals 5 and 6 on the regulator are the output to the field.

Initially, you described a voltage flucuation problem. When did that occur - what load? Doesn't seem like you've done anything to fix that, uless it *was* just a dirty switch contact, as originally suggested. Is that symptom gone now?

[rexydg]

ok one more time.. the generator does not poduce any voltage when I start it... the voltmeter and freq.meter sit at 0.... when I reach inside the panel and push the manual flash switch to the left.... the volts and freq will come up to the right readings after about 5 seconds of holding the switch.

At that time I can run most things and there is no drop in rpm or freq. when I apply heavy load [water heater, microwave, stove elements] the rpm drops a very small amount, the freq. stays at 59-60 and voltage is about 210-220 the % load meter shows about half. the engine is in impeccable shape and it has plenty of power, the stop is fine.. all of the engine components are 100%.

Now I guess what im asking is this... why do I have to use the manual flash switch to get my power started, when this was never an issue before.. I would start the set and it was there.

and also the unit would produce enough power surge before to start the A/C unit with less than 3 seconds of rpm drop of the set.. the A/C would be running.

What item of breakage would cause these two things to happen?

also the number 5-6 terminals never had the wires removed so they are not reversed.

what capacitor, diode, switch, relay..whatever is responsible for ensuring the surge is there when it is called for. and what object is responsible for flashing the "field" without the use of the manual switch... which I never had to use before?