Maximum inefficiency

[fuelfarmer]

How is this for making 3 phase 460 out diesel fuel in just a few easy steps. The irrigation system needs 3 phase 460 volt power to run the tower wheel drive motors. The tractor is powering a single phase generator, that is powering a 10 hp motor, that is powering a 3 phase generator, that is powering the drive motors on the irrigation towers. Later we will use grid single phase power to run the motor to generate 3 phase power.



 

[Apogee]

I think it could be made better by putting a fan on the end of the tractor pto, then putting another fan on the single phase genhead. 
Then you'd want to face them toward each other so they would be "air coupled..."

LOL!

Gotta hand it to you though, it gets the job done!

Best,

Steve

[Ronmar]

Or you could get another PTO gearbox and spin the 3 phase generator directly from the tractor PTO...

[Thob]

I think you need to get that Lincoln "tombstone" welder in the mix too - that should lower the efficiency a little more!

Where's the water pipe?  Is there a piece missing between the center pivot and the concrete?  It really doesn't do much good to have the sprinkler going around in circles if there's no water!  I assume you've got a well or water source of some kind...

Is that your canola you're watering?  Are you having drought conditions there?  It's been raining about once a week here, sometimes 1/4" and sometimes 2" so I think we're about out of the drought.  The rest of Texas isn't doing as well, but still better than last summer.

[LowGear]

That Ronmar always has great suggestions.

I was wondering how much a single phase motor or two out on the boom wheel would cost?

The air coupling must be hard to pass up as well.

Casey

[TimSR2]

Now that's Entropy... 

[mbryner]

This is hilarious!   Apogee's "fan coupling" solution is awesome.

Does the whole irrigation system move intermittently or constantly rotate?      What about one of our famously thrifty Changfoids or Listeroids powering a 3 phase generator out there instead of grid power?   Grid close by?  What about that guy running a tiny generator to power all that 3 phase equipment?  Can you really run three phase motors on single phase w/ a mod?   Itchin' to hear more of the story...

[fuelfarmer]

That set up is just to do a test run, or walk, of the towers on a new install of a used system. The under ground water feed pipe will be installed soon. We pump from a river.

There is canola on some of the land this system will cover, but we will not water in the winter. If it is dry in the spring, water will fly for sure.

The reason for high voltage 3 phase is the drive motors can be a long way from the control panel. Voltage drop would be a problem without very big wire if low voltage was used.

We though about running a small diesel generator, but we have single phase grid power close enough to run some under ground wire and use a single phase motor to run a generator to make high voltage 3 phase.

The motors on the drive wheels start and stop as needed to stay in line. The end drive motor is the master and the rest just keep up by using micro switches at the joints. . The older systems I think used an on/off timer on the master motor to control speed. I think VFDs are used on new systems. I could be wrong.    

[BioHazard]

That's some hard core generator porn. 

[vdubnut62]

I did see a post on here somewhere about a "Rube Goldberg" outfit. Seems it was possibly misplaced.
Ron.

[LowGear]

First, I understand the selection of motors on the boom were not fuelfarmers decision so"

The reason for high voltage 3 phase is the drive motors can be a long way from the control panel. Voltage drop would be a problem without very big wire if low voltage was used.

Makes my brain feel all fuzzy.  This is a dangerous situation as fuzzy on top of dizzy is a dangerous way to operate machinery and I can hear my mower calling out through the pineapple and papaya.  So here's the educational opportunity that I so enjoy on this website.

1.   Doesn't 3 phase and 1 phase normally use the same voltages where 3 phase greatly reduces individual conductor current?

2.   If 1 phase drives the motor that runs the 3 phase generator then hasn't the really long run of conductors already been 1 phase?

3.   As many of you know; converting 1 phase to 3 phase is extremely common especially in the commercial world.  Why?

Casey

[Ronmar]

He probably dosn't have 3 phase available at the source/start of his below ground wire run, hence the need for the conversion...

[dieselgman]

Casey, I think you are basically right... but the boom wiring portion (likely 1/4 mile) reduces the current requirements and voltage drop if run at 480vac - at least for that portion of the run.

3-phase generally has available high-voltage (480) whereas single phase will only do 240. Higher voltage = less current requirement. You do get the benefit of only needing a single neutral lead for all three power legs with a properly wired 3-phase system. This is one reason most commercial wiring is configured 3-phase. The other primary reason is motor efficiency.

dieselgman

[LowGear]

Hi dieselgman,

I get the part out to the base. 

And I understand "that's the way we do it". 

And we know single phase can cough up the watts. 

But my question is that doesn't each conductor carry about the same voltage whether it's single phase or three phase?  Granted the current flow is the killer (watt for watt about 1/3 to 1/4 the current).  I wonder what the actual wattage flow is to one of these rigs?

Casey

[dieselgman]

I am sure there is considerable variance between setups and different size towers but a typical generator requirement for them is 15kW and that is wired at 480v.

The conductors don't so much 'care' about the voltage as much as current but the two are related per Ohm's Law (E=I x R) - Up the voltage and thereby reduce the current requirement for a given amount of work.

In this example as I understand it, incoming single phase voltage will be 240vac and converted voltage (at the pivot) will be 460 [or 480] typical. Only half of the circuit will enjoy the higher voltage benefit - but better half than none.


dieselgman