10KW Homemade generator

have_blue · Sep 20, 2004

( Saw this at a new Harbor Freight )

Hi Bob,

I've had my eye on that deal myself.

Problem is, it would need nearly a 10:1 pulley ratio to make it work.

You could make a pair of 3:1 double reduction (speedup) set. The first pulley would kick it up to 1620, and the second to 4860 RPM. Now you can back off the 4860 until you get 3600 RPM, and your engine would run at an efficient speed. You would probably need 35-40 PTO hp to run a pair of 3:1 sets. If you only have say 25hp, you would have to go with a 3:1 and a 2:1 and run the PTO a little above 540 to still get 20hp at the PTO. That's pushing a little.

slowrev · Sep 20, 2004

"A 12 pole, generator with the PTO running @600 rpm generator would have a frequency of 60 Hz."

One thought from here is that with the slower turnig generators, wouldn't an engine speed variation have a larger impact on the output frequency ?

TWINKLE_TOES · Sep 22, 2004

Three Phase Motors as Generators

You can buy it new or used from Amazon or borrow mine if you like.

rockinmywaypa · Sep 22, 2004

Thanks Twinkle Toes Looks like just what the doctor ordered. I'll check it out at the library but thanks for offering yours.

EdK · Sep 22, 2004

I'll bite-

Would you mind jotting a few sentences on that topic? It's an intriguing topic. I'll buy the book if your intro grabs me /forums/images/graemlins/smile.gif

have_blue · Sep 23, 2004

( "A 12 pole, generator with the PTO running @600 rpm generator would have a frequency of 60 Hz."

One thought from here is that with the slower turnig generators, wouldn't an engine speed variation have a larger impact on the output frequency ? )

I suspect that RPM on slower turning generators would have to be more accurate and stable than faster turning generators. The good news is that super-accurate frequency is not real critical for most things you normally need in an emergency. Even TV's and computers are pretty tolerant of frequency variation.

TWINKLE_TOES · Sep 23, 2004

Ed, I dug up this link which will give you an idea how this works. Nigel Smiths book is more technical and provides more detailed information on "why as opposed to "what"

Induction Motors as Generators

TWINKLE_TOES · Sep 23, 2004

slowrev,
 wouldn't an engine speed variation have a larger impact on the output frequency ?


Good point, the 600RPM would have a frequency sensitivity of 1Hz/Rpm, the 3600 RPM would have a sensitivity of 0.167 Hz/RPM, one sixth as much.

Have Blue (deep Tan Man) also makes a good point that most things are not terribly sensitive to frequency

Soundguy · Sep 23, 2004

1HZ per 10rpm right?

Soundguy

EdK · Sep 23, 2004

Thanks Twinkle Toes!

That served as a good intro.

Ed

TWINKLE_TOES · Sep 24, 2004

1HZ per 10rpm right?


Chris, you are correct /forums/images/graemlins/blush.gif. Thanks for catching my mistake. The 6:1 sensitivity for RPM of a 600 Vs a 3600 is correct.

600 RPM - 10RPM/Hz
3600RPM- 60 RPM/Hz

XmasTreeGrower · Sep 24, 2004

Just getting back to the subject of the original post of how the Harbor Freight generator head performs. I picked one of these up last week in the wake of Ivan since there weren't any kind of generators available anywhere on the East coast from Virginia to Florida! This, and some "Mountaineer Ingenuity", was all I could come up with for emergency power.

I put a 4" pulley on the 1" main shaft, and ran this off the front PTO pulley from my Steiner tractor. I just set the generator head on a pallet, staked in all four sides with some rebar, and ran a belt from the Steiner to the generator head. The Steiner uses a 18 hp Briggs motor that turns 3600 rpm, and it was easy to tune the top speed of the governor to produce the right voltage.

The setup ran great for three days, running one freezer, one refrigerator, an electric water heater, and produced clean enough voltage to run my computer and TV with no problems.

For $300, I was very pleased with its performance. I can see how you could easily couple the generator head directly to any horizontal shaft lawnmower engine with a Lovejoy coupler. If you could pick up an old Cub Cadet or Sears Suburban tractor with a good motor (usually horizontal shaft engines) for a reasonable price, you could have a very workable setup for less than $600. If you study all of the PTO generator set ups closely, you will see a gearbox that will spin the generator head up to the required RPM. Maybe these gearboxes are available for a reasonable price?

BTW, nothing is more appreciated by the neighbors than a hot shower after three days, when their "little" Home Depot type generators just won't cut it trying to run electric hot water heaters. Definitely something to consider when your sizing up your generator requirements!

Thanks
Bill

KiotiMutt · Sep 24, 2004

I've been searching high and low for the gearbox you refer to with no luck. If anyone knows where I can get one please let me know.

thanks,
KiotiMutt

Charlie_in_TX · Sep 27, 2004

( "A 12 pole, generator with the PTO running @600 rpm generator would have a frequency of 60 Hz."

One thought from here is that with the slower turnig generators, wouldn't an engine speed variation have a larger impact on the output frequency ?

)
No, engine speed will have the same effect weather it is a 12 pole generator turning at 600rpm or a 2 pole at 3600rpm. I will set up a senerio (set up so the math is easy). A tractor that the motor turns 3600rpm when the PTO is at 600rpm.

Senerio 1: 12 pole hooked to the PTO. In order to get a 1Hz change the PTO will change 10rpm. The motor will change 60rpm.

Senerio 2: 2 pole hooked to the PTO thru a 6:1 step up belt arangment. In order to get a 1Hz change the gen will change 60rpm. The PTO will change 10rpm and the motor will change 60rpm.

JazzDad · Sep 30, 2004

Have_Blue touched on the problem: feedback control. When the load changes, you need something to automatically adjust the throttle (perhaps only slightly). True, most of your load is not highly sensitive to the frequency. But don't run the spreadsheets on the computer plugged into his set up. /forums/images/graemlins/smirk.gif

BobB · Oct 1, 2004

JazzDad, (And other posters)
I'm not sure I agree with your replies.
I see many other pto 540 rpm generators that use a 3600 rpm generator heads. I have listed a few below. Are you telling me these do not work??? (Or work reliably?)

Voltmaster 30KW Genny

Winco 7KW Genny

I see many other companies that have 3600 rpm genny heads. Just can't find a supplier for the geared adapter. (Increaser)

Bob

Soundguy · Oct 4, 2004

( Have_Blue touched on the problem: feedback control. When the load changes, you need something to automatically adjust the throttle )

Congratulations! /forums/images/graemlins/grin.gif You've just described the tractors governor. When load rises, the governor adjusts the throttle in an attempt to keep the rpm constant. How fast and accurately the governor responds would be the issue. That said.. the governor on my old ford 8n from 1952 adequately powered my 12kw pto generator and the needle always stayed in the green zone between no load and 0-20 amps load.

Soundguy

Soundguy · Oct 4, 2004

Bob... it's my understanding that the pto gens northern tools sells are the 3600 rpm heads. The 12kw genny i bought from them, so far works flawlessly. With a vom and freq meter plugged in, I got less that 2 cycles difference when going from no load to 15-20 amps load from a power tool and heating element.. freq settled back at 60 and voltage went right to 121 after less than a second. I think most of that was the tractors governor responding. If I had it hooked up to my 90hp NH 7610s.. it probably wouldn't have changed at all...

Soundguy

Scozz · Oct 5, 2004

The PTO driven generator sold by utterpower has a "variable pitch" pulley on the PTO drive side. This pulley is adjustable by loostening a set screw and "dialing" the pulley in or out to increase or decrease the diameter. Using this set-up it would be rather easy to tune the RPM's to meet your requirements.
These pulleys are readily available from any HVAC wholesaler ... we use them on HVAC blower motors to adjust CFM output.

Jim_W · Oct 10, 2004

Another consideration is whether you want to tie up your tractor during natural disasters. If you have a generator with its own motor, you do have one more engine to maintain, but you will be able to help people out with your tractor while your separate generator is powering the vital stuff in your house.
I thought I could get a generator happening inexpensively by using the pto but then I stumbled into a deal on an old self-contained unit - thereby ensuring we won't have power failures around here anymore /forums/images/graemlins/wink.gif
Whatever you end up with, make sure it has wheels!