Run a 3600 RPM genset @ 1800 ?

[Sparky01]

Hello everyone. I am installing a Winco 7KW propane Genset. It is a 3600 screaming banshee. It can output 3500 watt per leg. My question is can I lower the governer to 1800 rpm and get my 120VAC across what was my 240VAC legs and cap off the center tap that would now be about 60VAC? This way I get a genset that is quieter, last longer and I have no use for 240VAC.  Thanks for everyones help

PS: I am finally up to about 85% Green Power

[Titantornado]

Disclaimer:  I'm only guessing here.

I think power will drop to 1/8 the power at half the RPM.  And, the frequency will only be half that of normal.

Now, let's have someone who really knows answer, and see if I guessed correctly.

[Flux]

Possibly but probably not. Depends on the excitation scheme of the alternator. If it is capacitor brushless it will not excite. If it has an Avr you will need to modify the voltage feedback.

You will have half frequency and you will only be able to use loads that don't object ( even lights will flicker)

You will only manage about about 1 1/2 kW.

Not really viable.

Flux

[wpowokal]

I concure with Flux. As it depends what type of generator you have but you run the risk of burning out the rotor (field) at half speed.

There are emf's (voltages) and counter emf's within a generator, low speed loading can lead to too little of the later and a melted rotor.

allan down under.

[Sparky01]

Thanks for the input. I was only thinking voltage and forgot about Hz output. Darn I thought that it was too simple.

[Ungrounded Lightning Rod]

If it is capacitor brushless it will not excite.

But you can get it to excite by doubling the capacitance.

As flux points out:  Output half-normal (normal current, half voltage).  Fine for heating, LARGE incandescents.  Not good for lighting otherwise:  Small incandescents will flicker, compact fluorescents may light or blink, but will burn out quickly unless they have oversize capacitors in their raw supply.  Will burn up (literally - fire hazard!) 120v inductive loads intended for 60 Hz (wall warts, transformer-based power supplies, motors, inductor-balasted fluorescent fixtures - which will also draw excessive current, overheat, AND flicker horribly).  A particular risk is a shaded-pole bathroom fan, which is likely to start a fire in the ceiling.  Switching power supplies for electronics (i.e. computers) will have half capacity output, so output voltage will droop with normal loads and/or be more susceptable to voltage dips if they do work.

You could use 240V transformers at half voltage primary and secondary.  Large 240V motors will run at half power and half speed (if you double up any start/run caps).

[Ungrounded Lightning Rod]

But you can get it to excite by doubling the capacitance.

(Make that a maybe.  Depends on whether the rotor winding's resistance is low enough to keep the field up at half-frequency.)

[Phssthpok]

Just a thought...

How is it set up? Direct drive? Belt drive?

Is there any way to "re-gear" the output of the powerplant at a 1:2 ratio to the gen-head? That would drop your powerplant RPM to 1800, yet allow you to maintain 3600 at the gen-head.

Of course you may lose some power capacity since the engine isn't running at it's 'rated' RPM for peak performance, but then how close to max capacity are you running your loads ?

[RogerAS]

Hey,

"They" make a 1800 rpm 60 hrtz 110V generator head which employs 4 coils instead of 2. Who? I don't know do a Google search for them. I've considered such for my Kubota 300. My small diesel likes to run at 1800-2000 rpm, so I MUST gear up to get 60hrtz from mornal 3600 rpm genheads. If I had one of these 4 pole machines I could more closely match engine best rpm to genhead output cycles. Form what I've seen they're not cheap, but there's always that option, for me.

Now, what make of engine is powering the genset? Does the current genhead have a coupler from the engine crank to the genhead shaft, or is the engine itself serving as the genhead inside bearing? If it is a coupled type you can easily modify the gearing, if it's the other type don't mess with it too much. The later also has an engine oil seal to worry about between the block and long crankshaft bolted to the genhead rotor. If engine or genhead fail, in the later, the entire machine must come apart. In the former a failure means removing one or the other, maybe.

Unless and until I make my own biodiesel, like Pepa is, I really don't like running the Kubota at all. I'm extremely pleased with my solar array. If I could only match or exceed the 750W PV with a wind machine (or 2)......

Good luck,

[Ungrounded Lightning Rod]

My small diesel likes to run at 1800-2000 rpm, so I MUST gear up to get 60hrtz from mornal 3600 rpm genheads. If I had one of these 4 pole machines I could more closely match engine best rpm to genhead output cycles.

You could make one out of a four-pole motor.  Get a three-phase and hang caps on it to resonate it at 60 Hz, or do the same with the start winding of a single phase.  (Or maybe a smaller cap on the run winding and rectify the start winding for battery charging.)  It should take off and start genning once the RPM is maybe 25-50 over the resonance.  (If it doesn't, try flashing one of the windings to get a little magnetization into the rotor.)  Voltage is regulated by rotor saturation so it may come out a tad high, espsecially when not under load.

You can also use a faster motor with bigger caps to resonate lower and thus run it at a lower RMP at a proportionally lower Hz and voltage (though it gets harder to maintain excitation so you get less output current before it sucks out, a double-whammy on excitation losses as a fraction of output current).

Or just get some magnets and convert it to a PM genny.  B-)

Unless and until I make my own biodiesel, like Pepa is, I really don't like running the Kubota at all. I'm extremely pleased with my solar array.

Have you talked to the local oriental restaurants about disposing of their waste deep-frying oil for them?