MEP 017a Low Voltage output ?

[crazymechanic]

Hello all Im looking for help with 2 generators
I just Picked up a mep002a I got it running after new fuel filters and oil change and batteries , cleaned the fuel check valve here is the problem .

1 MEP002 a problem : After a few minutes of running great , it just cuts off on its own, I can watch the selonoid on injection pump hammer down and the battery indicator gauge goes to nothing like im turning it off or something ?

I have great oil pressure ,good batteries, I do only have about a gallon of fuel in it.


2. MEP017 problem :Very Low voltage coming out of 120 socket wont run a vacuum cleaner , voltage guage on gen says around 55 volts ?

I have changed all fluids and batteries , Runs like a top (Tag says last serviced 1 hr ago on meter In 2008 812 hrs ) I have switched all the setttings around it dosnt seem to change voltage output .

Any Help would be greatly apreciated Im new to Military generators !!!

 

[Keith_J]

For the 002A, sounds like either the high temperature or low oil pressure switches are breaking continuity, causing the fuel cut-off solenoid to lose power and shut the engine off. The low oil pressure switch is supposed to break at 12-14 PSI. The switch made by Hobbs is adjustable, pull the rubber plug and note the hex plug under it. Clockwise is higher pressure cut-off. Verify with accurate gauge.

On the 017, this sounds like the variable resistor on the panel is failing. Measure its resistance over the entire range. Tuner/contact cleaner can help. This could also be diodes on the field exciter rectifier assembly. I'm a bit rusty on the 017a as it has been 22 years since I've used one.

 

[panzerwillie]

On the gasoline one make sure the engine is running at 3600RPM, usually the herzt gauge should be at 60 HZT
plus is very loud, you can disconect he field wires of the VOLTAGE regulator and hit the positive and negative with 12 volts it should go up if the diodes are good, if it does then the VR is bad if not the diodes like KEITH_J mention need to be replace, is being a while for me to good luck

 

[Keith_J]

I guess a little course on how these generators work is warranted. If you had physics back in high school, you know that a magnetic field moving through a coil generates electricity. In both automotive alternators and these, the magnet moves and the magnet is an electromagnet. Unlike the automotive alternators, the MEP's electromagnet isn't supplied through sliprings and brushes but something called an exciter.

This device is just another alternator, only it is a moving coil in a stationary field coil, an electromagnet. The moving coil is attached to the main field coil, the electromagnet which drives output. But this moving coil generates three phase AC, unsuitable for the main generator field which needs DC. So this AC is fed through a three phase full bridge rectifier, composed of six diodes which then feed into the main field.

Now how does the generator regulate voltage? Simply, it regulates the exciter field current. This regulates the rotating field current which regulates the output voltage, respective of the load on the generator.

The load is simply connected with the stator coils.

Frequency is stabilized by the engine's governor since these generators are synchronous, meaning frequency is from the rotation of the field in the stator.

Yes, there are TWO "generators" in the generator head, the exciter-field generator (which doesn't produce any usable power) and the field-stator (which produces power, when connected to a load).

 

[crazymechanic]

thanks so much for the helpfull info keith&panzerville nice write up .
turns out I have a FLRC-Lumberton Mdl MEP-016E 3 KW 60 Hz diesel engine generator not a 017 the other
is a the 1988 Libby Corp Mdl MEP-012A 5 KW 60 Hz diesel engine sorry
about that ....
I will post some pics of the electronics behind the board on the 016 it looks a little bad to me alot of corrosion on the diodes

the mep002 I will test light the switches and see wich one is cutting it off , because it has good oil pressure and i noticed it wont start or stay running when cranking unless the oil pressure comes up then i can let off the
key and it will stay running .

What sucks is I have my hands full looking for work Zero income and I thought they might be a easy flip to make a few hundred bucks BIG wrong I might keep the 1988 Libby Corp Mdl MEP-012A 5 KW 60 Hz diesel engine generator beause of the sound supression .
So I guess its a priority to get the 016 fixed

 

[Keith_J]

Don't need to spend ANYTHING to check/inspect so keep your wallet in your pocket. On the variable resistor, they get corroded on the wiper. A shot of WD-40, then run the knob back and forth a dozen times, then another shot should work wonders. Yes, WD-40. Ok, you might have to buy that. If all you have is a test light, diodes can be checked but you must know how a diode works. Think of it as a check valve. A one-way valve. The electrical symbol is the key to how they let current flow one way, blocking the other

Lets see if ASCII text will work...mods, this isn't chat text, it is ASCII electronics

Current flows + --->|---- - where the + is positive and - is negative

Current doesn't flow - ---->|---- +

Naturally, you will need to isolate the diodes from the circuit and they are soldered in.

Another possible issue is the engine isn't running at full governed 3600 RPM. This is a 2-pole field which produces 60 Hz frequency. If you don't have 60 Hz, the exciter won't produce enough current for the field to make full voltage.

On the 002A, sometimes the high temperature cut-out gets too sensitive. Be sure the flap covering the fuel cutoff solenoid (governor solenoid) is shut, otherwise the high temperature cutoff will trip. The more it trips, the more sensitive it gets. The low oil pressure cutoffs like to get corroded, not on the contacts but on the steel base. If yours has been stored outside, that is probably the case. They don't work right when corroded. The contacts are gold-plated silver, a new switch can be obtained here:
Advance Switch, Pressure, 15 PSI, M4008-15

This is the exact part, adjustable too. If yours looks like this, just remove the rubber center cap and back out the hex plug a few turns. This will reduce the trip pressure. You can always set it back to 14 PSI calibration with air pressure test.

 

[crazymechanic]

thanks keith J
i will get on it on sunday and figure it out Im assumning the metal flap door is what your talking about because the air will blow out and not cool , anyway il get some feed back I just found a freind with a 24 volt charger and did wonders to the battery tonight should be good on sunday

 

[PeterD]

...

Lets see if ASCII text will work...mods, this isn't chat text, it is ASCII electronics

Current flows + --->|---- - where the + is positive and - is negative

Current doesn't flow - ---->|---- +

...

Gee, with that diagram we're not going to ignite the old fire fight about current flow are we? (while the above ascii art is accurate, it simplifies things too much!) Current (electrons) flows from negative to positive, it always has, and always will. Some try to bend that around so it is more logical by calling current flow 'holes', but as far as I'm concerned, that just makes things more confusing. The fact is, we have made things very confusing because when electricity was first 'made' (batteries) they didn't have any idea what terminal had the excess of electrons and what terminal has the shortage!

A couple of web sites that may make it clearer are:
Introduction : DIODES AND RECTIFIERS
and
http://en.wikipedia.org/wiki/Diode

I like the first URL's reference best, it is very clear, and I'd suggest anyone who has a question on diodes/rectifiers take a look at it.

 

[Keith_J]

Yes, Pete, I know the primary charge carrier is the electron which is a negative charge. This is Steel Soldiers, not physics forums. Besides, I left enough ambiguity in my diagram to allow for the negative charge carrier convention. Only if you are a polymath and know a bit of hydraulics schematics do you see the check valve analogy

 

[PeterD]

I'm originally a EE, and you would not believe the bloody fights I've seen over the topic! Without a doubt it will give you a headache thinking about it, considering all the different factors into what makes both electricity and what positive and negative are!

 

[Keith_J]

I knew it, you are a plumber of electrons . Getting back to the generator, it is unlikely that exciter-field diodes are bad, more likely it is just inadequate engine speed or the variable resistor is weathered on the wiper. I've already suggested a remedy for the latter, it worked in my 002A which had been exposed to weather, causing problems in four gauges (current, frequency, voltage a and oil pressure). No, FIVE gauges, forgot the fuel level. All but the frequency gauge are now working.

 

[PeterD]

OK, I confess... Also I'm a university teacher, which is even worse!

Agreed, I suspect the variable resistor more than anything else at this stage, and since it is an easy test (and repair) maybe one will get lucky.

 

[crazymechanic]

OK ...
THE Mep 012 has a bad or whatever oil switch I bypassed it and it stays running verified it has over 30lbs of oil pressure ok I can deal with it


And I have New problem Batteriess are not charging at all does it have to have 24 volts to charge because mine were runnning low by the time I checked it out Regardless its not even putting out any + volts when running it goes Down . Now what ?

the 016e I have the panel open with pics it has directions to flash

1 do i disconnect them from the board and flash the 2 wires with 12 volts or just touch the 2 screws or do i disconnect the terminals wires and hit the screws ?

 

[panzerwillie]

Just flash the wires , take them of the AVR, make sure you have a voltmeter conected, so you can see if the voltage goes up.. a minute more less

 

[crazymechanic]

OK how would the voltage go up ? are you talking about doing it while its running ?

 

[panzerwillie]

i gave u my number twice call me will explain it better , tomorrow after 11 AM

 

[crazymechanic]

Will Do.

 

[crazymechanic]

Hey great news after i flashed the mep016e it started working well its putting out 120 so far i have to read the manual to figure out how to load test it ..thanks for your help on this one

now the Mep012 is working with some weird bugs its not charging batteries and if it sitss for a while a day for some reason it dosnt kick the selonoid of the fuel pump ?

 

[Keith_J]

You mean MEP-002A? If so, the battery charging issue could be a blow fuse. Look under the fuel cut-off solenoid, on the vertical panel near the oil filter. A round fuse boss.

The fuel cut-off solenoid is bypassed in the startup connection which puts voltage to terminal 28 of switch S1 when in the most clockwise position (start, spring momentary). If the oil pressure and over-temperature cut-offs are working, relay K1 can have issues, just flip it over as there are redundant connections and rotational symmetry in its 2x4 pin package.

 

[crazymechanic]

OK sounds good Il try that tommorow