Running a generator underspeed

Discussion in 'General Technical Questions and Answers' started by TJNII, Jul 30, 2021.

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  1. K7JEM

    K7JEM Ham Member QRZ Page

    I have a 25KW diesel generator that I run 24/7 at one of my communications sites. We provide power for ATT and T-Mobile as well as all of the other comm stuff in the building. We also provide power for US Border Patrol, which is in a building next to ours. The annual diesel bill is around $32,000 for that generator alone.
    K0UO likes this.
  2. K6BRN

    K6BRN XML Subscriber QRZ Page

    Prime power vs. standby power. Prime power generators are mostly diesel, do not respond well to light loads for extended periods, have much more capacity and much less efficiency at light loads than 99% of homeowners and hams desire. So ... not very applicable to most.

    Now - if you're a power provider, as K7JEM is, then the weight, capacity, initial purchase/install expense, maintenence and operating costs of using prime power rated generation makes a lot of sense. And costs are recouped. But most people are simply not in that situation.

    In standby generators, Honda inverters are hard to beat, and you pay (once) for quality and benefit forever from their clean power, efficiency and reliability. I have three units.

    I've used Hondas since 1999 and never regretted switching over to their inverter technology. My last use was was when hurricane Henri hit CT this August and my EU2200is kept the 8,000 BTU A/C. lights and fridge on at my lake house. In CA I use an EU6500is, as do some of my friends (the EU6500, EU7000, EU2000 and EU2200 are all very popular among the engineering community here). I even have a little EU1000 with heaven knows how many hours on it - but its ideal for running a ham station when portable (29 lbs) or the power is out - it sips gas and rapidly adapts to load changes - while maintaining frequency, voltage and power quality very, very well.

    Yes - you CAN buy a $99 ChiCo special AC generator. And it may even work for a while, burning a gas/oil mix and without much regulation or capacity. Or for about three times as much buy one that burns regular gas, or for bit more, even Diesel. But you will get just what you pay for. In every way.

    (Check YouTube for "Diesel Generator First and Last Start")

    Regardless, like KM1H, I tend to accumulate ... stuff (though I've recently purged quite a bit in a home renovation). So I still have my old (pre-corporate reorg.) Generac 4000XL from the 1980's. Electronically voltage regulated, mechanically frequency regulated, full pressure oil lubrication, automobile oil filter, very maintainable and adjustable (and drifty). But noisy, inefficient and with much poorer power quality than the Hondas. I loan it out during outages.

    Brian - K6BRN
  3. PU2OZT

    PU2OZT Ham Member QRZ Page

    Absolutely no tractor engines experience, so a dumb suggestion... adding an hydraulic motor-pump between your engine and the generator should be safe electrically, mechanically and thermodynamically.

    How about this one, 100,000 HP @ 100 RPM
    While this is “only” a 12-cylinder version of Wartsila’s RT-flex96C low speed turbocharged diesel engine, the larger 14-cylinder version takes top honors as the largest internal combustion engine in the world, at least for now. Weighing 2,300 tons, it’s 44 feet high, almost 90-feet long, and produces 5.6-million lbs. ft. of torque and over 100,000 horsepower at 102 rpm.

    Ain't gorgeous!

    UT7UX, KF4ZGZ and K0UO like this.
  4. N3HGB

    N3HGB Ham Member QRZ Page

    If you want really quiet power, I read about an off-grid guy that hooked a couple 48 volt alternators to an old Dodge straight-6 he got from a junkyard. The alternators charged a 48 volt battery bank that connected to a big inverter. The engine gave him sufficient power just off idle and he got a huge muffler from somewhere.
  5. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    Growing up working on farms and in orchards .....
    Tractor mufflers are generally the size of car mufflers already, so ......
    Maybe one from a Prius or Tesla?
  6. KM1H

    KM1H Ham Member QRZ Page

    BUT we are talking about 3600 rpm small engine generators, 10-15 hp, not farm tractors that run just fine at low rpm's.
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    Seems that the proper gears should be used.

    Use a Muncie T10 with the Flywheel attached. :)
  8. N5TJD

    N5TJD XML Subscriber QRZ Page

    Some tractors have reversable PTO stub shafts, on one orientation it spins 1000rpm, reverse it and it is 540....

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