Load balancing on an MEP-805B

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diogenescreosote

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I have an MEP-805B which I am planning to use to drive some 480V loads. Based on my understanding of TM 9-6115-671-14, table 1-2 on page 1-15, it is possible to get three distinct phases of 480V by setting the mode to 240/416V nominal, then cranking up the voltage regulator until it hits 480V. Is this correct?

Assuming it is, then I have another problem. I basically only have two 480V loads, and they aren't equal—not sure exactly, but something like 10 kW and 8 kW. So the three phases would be differentially laden: 10 kW, 8 kW, and 0 kW. My concern is that such extreme imbalance will somehow damage the generator head, perhaps by making it shake or putting sideways force on the bearings.

I cannot find any guidance in the TM about how important it is to balance load among the phases. What are people's thoughts here?
 

uscgmatt

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You have 2 480 volt single phase loads? If so, the unloaded phase will generate heat that has to be dissipated by the generator head. It wont shake or side load the generator. The generator is making the same amperage on all 3 phases it's just has no where to go so it becomes heat. 3 phase generators are derated by 1/3 when running single phase. So as long as your total load is under that you should be good.
 
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diogenescreosote

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Yes, correct, two 480V single phase loads.

To what extent is the additional heat on the unused phase pair a problem? Will it eventually burn out the generator?

Would there be less heat on the unused winding if I added some "dummy" load on the unused phase pair, so that the head dissipates in some external thing (maybe a 480V heater, idk)?
 

uscgmatt

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Your generator is 30kw, so it would be 20 kw single phase, your 18kw is under that. That much heat it can displace with out doing damage. I would add a 5-8 kw load to the unused phase to reduce heat in the gen head. It will use more fuel, but it's better for the long term.
As for raising the voltage, is it in the spec for the set to be raised to that. I think that is in the TM.
 

155mm

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Another thread to read up on, discussions on over voltage of mep, subject is 804 but concept is exactly same..

 

155mm

Chief and Indian
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Courtesy copy for anyone else wondering about this, CC from youtube video comments.

Screenshot_16.png


Screenshot_17.png
 

155mm

Chief and Indian
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I highly suggest if you truely need 2 legs of 480, use a commercially available generator, they are cheaper now, the oilfield is slowing so equipment will be available cheap.
 

diogenescreosote

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I did not get a chance to put this into practice, because I did not successfully acquire the 480V ballasts I expected. I have instead deployed the generator for a different purpose. I have had some issues setting it up, which I will post about in a different thread.
 

mciikurzroot

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wimberley texas
I have an MEP-805B which I am planning to use to drive some 480V loads. Based on my understanding of TM 9-6115-671-14, table 1-2 on page 1-15, it is possible to get three distinct phases of 480V by setting the mode to 240/416V nominal, then cranking up the voltage regulator until it hits 480V. Is this correct?

Assuming it is, then I have another problem. I basically only have two 480V loads, and they aren't equal—not sure exactly, but something like 10 kW and 8 kW. So the three phases would be differentially laden: 10 kW, 8 kW, and 0 kW. My concern is that such extreme imbalance will somehow damage the generator head, perhaps by making it shake or putting sideways force on the bearings.

I cannot find any guidance in the TM about how important it is to balance load among the phases. What are people's thoughts here?
What part of this am i missing, WHY do both of the 480 loads have to be one one set of output phases, ie. it seems to my reading in your example, you are for discussion, going to use L1 and L2 for BOTH loads.. Why not use the one load between phases's 1-2 and the second load between phases's 2-3 that's plenty close enuff of balancing to settle any discussion IMO..

Now the voltage output level is a whole nother discussion. as has been cautioned your not likely to get 480 in just panel voltage pot adjustment and if you do it will be spotty and in my experience more nuisance faults than its worth.. In my career of electrical contracting your equipment will not suffer in the least being supplied by 460 volts, but if you're just that determined then go ahead, and further and personally would not be concerned to move into the 450 range [run your equipment and check for expected performances to be the deciding point] and then your internals of the set will function without all the nuisance fault issues.

BUT ? i live closer to the edge so i dont take up more room for others that want it.
your actual generator will perform well at 480 with no issues, its the alerts,warnings and fault set points that will be the pain in the ass to reset to accept the higher voltages, the actual regulator will respond to being adjusted to the higher range, , the OV relay sensing and the one potential transformer will come into consideration also. most of this nonsense can be well resolved, its just you're patience level or support help that will finally determine your success ... im working from memory with all this and too lazy to go dig out the manual and wiring schematic, but the convenience outlet should remain at 120 from where its picked off from, and this might carry to the potential xformer in the upper right side above the load board, but in my head im pretty sure it is sensing is from what now is the 240 voltage and increasing it to 265/277 can present issues, this might be solved easily, i just need to review the manual to be sure. to wrap this blab up, it will work, just a learning experience for you.
lets know or keep us informed.. mac/mc
 
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