Why are military generators so big?

[novaman]

Ive spent some time looking threw treads and havent found this topic yet. I've bought 2 mep-802a's now and one mep-002a. I love them. All only needed filters and fluids. Gave one to my father one for me and one to the inlaws. Super nice pieces of equipment. Really heavy duty looking and durable from what I've read. I know that a lot of size is the skid, large gauge cluster and large diesel engine which you need to make power at 1800 rpm. But why are the alternators so big compared to say a Kohler 20kw whole house standby gen head? I know I can get more kw ratings out of these mep's, I've tested them but it just seams like the head itself is either the same size or bigger then the whole house 20kw units. Thanks for the info.

 

[swbradley1]

To make little civilian generators envious.

 

[Gunzy]

"Size Matters." Sounded good to me.

 

[glassk]

2-Pole, Rotating Field




4-Pole, Rotating Field

 

[novaman]

So then its just that the 4 pole heads are significantly larger? Are the Kohler 20kw units brushless too?

 

[74M35A2]

No. I have a 4 pole gen head on a diesel construction site light tower that I use as my home standby genset, it is an 1800rpm Kubota D1105. It is no larger than the gen head as found on your typical 10hp gasoline portable 5000W 3600rpm genset.

I have seen the generator (alternator) head of a "2A", and it is huge. WildChild467 has one, and were talking about this recently. Of course this is speculation, but he had a pretty good guess in that the output from those gensets are configurable via a panel mounted switch. 1-phase, 3-phase, and a bunch of other knarly output options. Given this, there is likely several different winding sets in the alternator head, therefore increasing its size. Sure, there is always the more=better military stance of margin over-design, but to be that much bigger, I'd wager that it is mostly due to the additional windings of which some are used and unused at any point in time, depending upon switch setting.

A study of the wiring diagram of such would confirm.

Brushless does not make it any smaller or larger, that is just a different way of voltage regulation via rotor/stator resonance using capacitors for tuning, vs a voltage regulator and brush set.

 

[Daybreak]

Howdy,
The MEP-80x series are 120/240 single phase and 120/208 3 phase. Yes, they are also overbuilt to withstand 24/7 operation as well.

 

[rustystud]

No. I have a 4 pole gen head on a diesel construction site light tower that I use as my home standby genset, it is an 1800rpm Kubota D1105. It is no larger than the gen head as found on your typical 10hp gasoline portable 5000W 3600rpm genset.

I have seen the generator (alternator) head of a "2A", and it is huge. WildChild467 has one, and were talking about this recently. Of course this is speculation, but he had a pretty good guess in that the output from those gensets are configurable via a panel mounted switch. 1-phase, 3-phase, and a bunch of other knarly output options. Given this, there is likely several different winding sets in the alternator head, therefore increasing its size. Sure, there is always the more=better military stance of margin over-design, but to be that much bigger, I'd wager that it is mostly due to the additional windings of which some are used and unused at any point in time, depending upon switch setting.

A study of the wiring diagram of such would confirm.

Brushless does not make it any smaller or larger, that is just a different way of voltage regulation via rotor/stator resonance using capacitors for tuning, vs a voltage regulator and brush set.

You hit the nail on the head ! It is because it can do both 1 Phase and 3 Phase power. There are indeed two complete and separate sets of windings on this generator head. Also the engines are made out of cast iron, not aluminum. Iron is heavy ! but they last longer then aluminum .

 

[dependable]

The windings are indeed robust. But they are not different than any old style or commercial grade, well made 1800RPM, 12 lead connected generator. The MEP-002 and 003 use the same gen head as their respective counterparts in the Onan DJ series.

If you look up an Onan DJE for instance, you will see it has the same motor and gen head as an MEP. What it does not have in the output box with the reconnection switch, the control box with gauges and wireing, redundant fuel pumps and filters, built in forklift skid, all of which contribute to the MEPs overall size and weight.

The change from 1 phase to 3 phase is accomplished by re configuring the hook up of the 12 leads though the reconnection switch.

 

[novaman]

Thanks for all the info guys your giving me fuel for my flight with a guy at work ha-ha. There's two of us that are into military equipment and many more than aren't but still think there Bad A#$. But there's about two guys that just don't get it. I tried explaining power quality and durability and fuel storage shelf life vs gas but its falling on def ears. " my gas generac is 1/4 of the weight and size and works just as good and has more available parts" so most of this info is to support my mep addiction. Thanks again

 

[SCSG-G4]

novaman,

Give the naysayers a challenge. Run their generator and a similar sized MEP under full load 24/7 with the only shutdowns being for the required PM (100 hour oil and filter changes), for 3000 hours (125 days of running), or whichever one breaks down first! The MEP's are supposed to go 5000 hours between resets (208 days of continuous running). They will either be up to the challenge, or make excuses. "Put up or shut up!"

 

[novaman]

They'll Defiantly come up with more excuses but ill still say it.

 

[Gunzy]

I stand by my first statment.

 

[Csm Davis]

And as SCSG-G4 eloquently spelled out duty cycle! The civilian gensets are normally only rated for a few hours a day.

 

[Wildchild467]

I love my MEP-002A because its just rugged and will run for hours and hours on end. Built like a brick outhouse. Oh, you have to shut your civy generator down to put fuel in it? Not this guy... just plug a fuel line into it and flip the switch on the control panel. I love it!

 

[rustystud]

The windings are indeed robust. But they are not different than any old style or commercial grade, well made 1800RPM, 12 lead connected generator. The MEP-002 and 003 use the same gen head as their respective counterparts in the Onan DJ series.

If you look up an Onan DJE for instance, you will see it has the same motor and gen head as an MEP. What it does not have in the output box with the reconnection switch, the control box with gauges and wireing, redundant fuel pumps and filters, built in forklift skid, all of which contribute to the MEPs overall size and weight.

The change from 1 phase to 3 phase is accomplished by re configuring the hook up of the 12 leads though the reconnection switch.

If you didn't have the 12 leads you wouldn't have single and 3 phase capability. No single phase generator use's 12 leads. Yes the reconnection switch box adds weight but it doesn't explain the extra size of the generator head.

 

[dependable]

^^The size of the head is because they are robust and overbuilt. Where a modern "consumer grade" civilian generator rated a 5 KW means it can make 5KW for a few minuits at a time when it is new, 5KW on an MEP means it can make 7KW (at least in the case of the 002) all day, 24/7 for thousands of hours, and at any altitude.

There are single phase generators with 12 leads, sold that way from the factory. They are reconnectable, but must be done manually and not something most people would switch back and forth. 4 pole generators generally have 12 leads, though some have 10, and they are also reconnectable. In fact, even some non reconnectable generators have the same windings, but the leads are not carried outside the head. I believe the MEP-016B is has only 6 leads, yet is reconnectable, but is only a 2 pole generator..

I am sure you understand this, but it seemed by the wording like some may have thought there are, extra and different windings for 1 and 3 phase.

 

[novaman]

Im picking up what your putting down

 

[Isaac-1]

I agree with SCSG-G4 Have them put up or shut up, the MEP-002a /MEP 003a is rated to handle full load 24/7/365 in nearly any condition on the planet, Arctic to 120 degrees F, sea level to 8,000 ft, without derating, where a common residential standby generator is rated at running a variable load up to its rated load for up to 500 hours per year at around 86 degrees F and 1,000 ft altitude without derating. Also many of these residential standby generators are powered by lawnmower engines which have a 500-800 hour useless life before replacement, by comparison the MEP-002a / MEP-003a are powered by militerized versions of the Onan diesel J series industrial engine, which the military rates at 5,000 hours between rebuilds, their slightly less robust civilian cousins are known to often run well over 10,000 hours between major service, some are known to last over 20,000 hours.

 

[74M35A2]

I love my MEP-002A because its just rugged and will run for hours and hours on end. Built like a brick outhouse. Oh, you have to shut your civy generator down to put fuel in it? Not this guy... just plug a fuel line into it and flip the switch on the control panel. I love it!

When you did that with yours, it went "zap", and everything broke. My small Honda genset goes in the trunk of my car and anywhere I want, easily, including up and down stairs. I don't need it to work in the arctic or desert (though it may do just fine at). It ran all 3 days consecutively of the continuous power outage we had years ago across 1/4 of the mid-west. I'm probably on my own with this one, especially on an MV board, but my vote goes for the 2 hand carry Honda in this case. For home I have recently acquired a diesel light tower, which is a liquid cooled 1800rpm diesel Kubota 1.1L. To be parked behind the garage and wired into an auto transfer switch.