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Military MEP and Aircraft Gen-Sets MEP Mobile Electric Power, APU Auxiliary Power Unit and other military surplus generators.

Military MEP and Aircraft Gen-Sets

Can anyone help? MEP-017A


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  #21  
Old 05-07-2005, 03:33:09 PM
rexydg rexydg is offline
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Default Re: Can anyone help? MEP-017A

as far as voltage or freq. variations.. I dont seem to have any issues with them now. they both are rock solid once I manually flash the field and get them up to where they should be. once again.. why do I have to manually flash this to get it operational when it was never an issue.. and where did my surge capacity go?
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  #22  
Old 05-07-2005, 04:49:07 PM
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Jim McIntyre Jim McIntyre is offline
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Default Re: Can anyone help? MEP-017A

Quote:
Originally Posted by rexydg
What item of breakage would cause these two things to happen?
The voltage regulator COULD cause this. The electrical side of this genset is not as simple as you might hope. Nobody is going to say with certainty what the single source of your syptoms is based on a few email notes.

One more time for you on explaing what "object" is responsible for flashing the field without using the switch:

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. That's a simple test. If it still doesn't self excite, go buy a new voltage regulator and see what happens.

Oh - are you starting this with a load connected? Surely not, but *that* could impair the self exciting ability on start-up...
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  #23  
Old 05-07-2005, 05:55:25 PM
Jim Rankin Jim Rankin is offline
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Default Re: Can anyone help? MEP-017A

The question of what causes it to begin generating is an interesting one. I am also having trouble with a couple of generators right now. The Winco will make 26 VAC since I had the exciter rotor rewound, and the Caterpillar will work fine 120/208 wye, but creates overvoltage at 120/240 delta. Haven't figured out either yet.

My understanding is that the function of the voltage regulator is to take "bites" of AC voltage that the generator produces and create a DC field voltage (which produces a current in the rotating field) creating the correct magnetic field strength to keep the voltage regulated.

Initially there is only residual voltage available from the magnetic field retained by the steel laminations of the armature. The regulator probably has to take all the residual AC voltage and rectify it all to DC to excite the field at startup. Some regulators can start up with less voltage, some have to have more. If there are any problems with the exciter/regulator or the set, it will take more residual to get it up there, and it may not be enough, so you have to "flash it". If the set is under a load at startup, the residual is bled away and so it won't excite.

Once the voltage builds up the regulator has to start working and will have to take smaller bites of the AC (or AC rectified to DC really) and send into the field. If it was allowed to have the power it has during startup, the voltage would probably "hunt". Some regulators have an external "gain" addjustment which I would think is just a method of adjusting the "leverage" the regulator has in adjusting the field.

On the caterpillar set I have there is a separate buildup relay which essentially sends all the rectified DC current available to the field until the AC voltage builds up to some level like 30 volts. Then it switches over and lets the regulator circuits work. This function would be included in all V regulators in some fashon.

Jim
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  #24  
Old 05-07-2005, 06:56:35 PM
rexydg rexydg is offline
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Default Re: Can anyone help? MEP-017A

no I never start the genset with ANY load at all, I tried the switching of the wires and it did not make a difference.. it still would not bring up the voltage without using a manual override. Would the VR problem also cause the surge capability to dissapear?
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Old 05-07-2005, 09:29:31 PM
Jim Rankin Jim Rankin is offline
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Default Re: Can anyone help? MEP-017A

It is quite possible you have one problem or had one problem in the beginning which has created others. But heck it runs a bunch of stuff already, so how much could be wrong with it. A good volt/ohmeter/ with capacitance checking setting, a soldering iron, schematics and a good light can sometimes produce amazing results. My Onan VR board actually cost several $0.14 resisters to fix, plus a lot of time finding a schematic and getting the resisters, and the diodes I blew when I tried the wrong board in it "just to see". I'm still in shock 8>)

Or send the VR off to the repair shop if you cannot find anything wrong elsewhere.
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  #26  
Old 11-29-2007, 09:01:16 PM
Bill P Bill P is offline
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Default Re: Can anyone help? MEP-017A

Hi, rexydg. I came across this 3 years late looking for parts for my MEP-017. If this is still an issue, maybe I can help.
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  #27  
Old 12-01-2007, 10:17:24 AM
sarge155 sarge155 is offline
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Default Re: Can anyone help??...

Check Peter Gottlieb.com....He has all the TM on his web site for this machine that can be downloaded
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  #28  
Old 09-29-2017, 09:23:38 PM
sarge155 sarge155 is offline
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Default Re: Can anyone help??...

hello..do you have any idea where i can find the exciter for a mep-017a generator?? thx
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