Powering a 3-phase sawmill with single phase solar.

Say I wanted to power this mill:

TurboSawmill Manual Warrior swing-blade Sawmill

https://sawmill.shop/products/manual-warrior-swing-blade-sawmill?variant=36083726385315

equipped with this motor:


Global Green Three Phase DC Brake Motor 15hp/11kw
*11 132M 38 2935 90.6 0.88 19.9 7.9 35.6 2.3 3.2 20.7 18.9 0.020 58 12.1 20.7

from this solar rig:

https://permies.com/t/40/36943/permaculture-projects/solar-leviathan.

What needs to happen to make this work?  And what will be the resulting wattage?

I am wondering if I need to go from single-phase to 3-phase, probably at the saw.  Can you buy a converter for this?  How plug-and-play are we talking here?

Or is it possible that there is alternate wiring at the motor itself?

I've done some electrical, but I'm not fluent.  I don't know what most of the data above means, so this may be kind of a "talk to me like I'm a middle-schooler" moment.  

My experience with taking a current from 220 single phase to 3 phase using a converter has not been good. I ended up bringing in a commercial 3 phase line.   Using the inverter, the equipment, in this case a band saw, ran …but it ran poorly using the converter.

Beau Davidson wrote:Say I wanted to power this mill:

TurboSawmill Manual Warrior swing-blade Sawmill

https://sawmill.shop/products/manual-warrior-swing-blade-sawmill?variant=36083726385315

equipped with this motor:


Global Green Three Phase DC Brake Motor 15hp/11kw
*11 132M 38 2935 90.6 0.88 19.9 7.9 35.6 2.3 3.2 20.7 18.9 0.020 58 12.1 20.7

from this solar rig:

https://permies.com/t/40/36943/permaculture-projects/solar-leviathan.

What needs to happen to make this work?  And what will be the resulting wattage?

I am wondering if I need to go from single-phase to 3-phase, probably at the saw.  Can you buy a converter for this?  How plug-and-play are we talking here?

Or is it possible that there is alternate wiring at the motor itself?

I've done some electrical, but I'm not fluent.  I don't know what most of the data above means, so this may be kind of a "talk to me like I'm a middle-schooler" moment.  

The first question I would ask as a designer is why? Most of the sawmills I've ever seen, including the one in the picture, use a small engine. Next would be why 3 phase. It is more efficient but if the efficiency means you have to completely rebuild your solar system efficiency goes out the window. As far as I know the Sol ark, and Schneider can be stacked for 3 phase. I've heard of people doing 3 phase converters but they are pricey. It would put a hell of a strain On an inverter system as well...

The manufacturer only makes an electric motor available in 3-phase. They said they could make a mill without a motor, but sourcing and installing a motor is a task I'm not familiar with. Maybe that is a possible way to go.

It's a cool idea -- when sketched on the back of an napkin.

Personally, I am convinced that the devilish details of implementing such a system with the motor you suggest are deal-breakers. Even if your solar system can generate enough energy, there are two additional conversions in the system, and each one creates losses. More importantly, 3-phase mid-voltage wiring is not a backyard project.

Sorry to be a downer on your idea.

The image shows a unit with an attached petrol engine, why not but that configuration?

John C Daley wrote:The image shows a unit with an attached petrol engine, why not but that configuration?

We want an electric mill.  Lots of reasons.

Okay, who has thoughts on getting the mill with no motor, and sourcing and installing our own single-phase, smaller motor.  We're fine with it moving slower.  What are the other considerations?

I afraid I think this has comedy (in the Paul sense of the word) and lots of fuckery written all over it.  Not knowing much about big honking motors, I'd see if a single phase motor could be put in instead.  Or go with the 6" model which would require much less power than the 8".

Beau Davidson wrote:Okay, who has thoughts on getting the mill with no motor, and sourcing and installing our own single-phase, smaller motor.  We're fine with it moving slower.  What are the other considerations?

If it's constantly bogging down it could really suck to use.  But if it doesn't get the blade pinched and stays sharp it should be able to just be pulled through the log slower.

Too bad you can't get a biodiesel powered one....

Might a band saw style sawmill need less power?  I know it's a totally different style of sawmill...

Mike Haasl wrote:Might a band saw style sawmill need less power?  I know it's a totally different style of sawmill...

I know you know how lovely it is to sharpen a swing-blade...

Suffice to say we're not gonna go the band-saw route here.

That motor says it's 11,000 watts. The math says 11,190 for me. Any converter would add to that to make up for the losses. A three-phase motor should work on single-phase at a reduced power as far as I know, but you will have to have a way to get the motor spinning before turning it on as three-phase motors have no starter mechanism.

Too bad...  Off the shelf electric band saw mill: https://woodmizer.com/Store/Shop/Portable-Sawmills/LT15-Portable-Sawmill

Mike Haasl wrote:I afraid I think this has comedy (in the Paul sense of the word) and lots of fuckery written all over it.  Not knowing much about big honking motors, I'd see if a single phase motor could be put in instead.  Or go with the 6" model which would require much less power than the 8".

You want to draw me up some plans to install a single-phase? 110 would give you extra brownie points.

It's really hard to do remotely.  I'm not good at 3d cad so that wouldn't even work.  And I don't know the first thing about big motors.  But I think it could be done.

Beau Davidson wrote:

Mike Haasl wrote:I afraid I think this has comedy (in the Paul sense of the word) and lots of fuckery written all over it.  Not knowing much about big honking motors, I'd see if a single phase motor could be put in instead.  Or go with the 6" model which would require much less power than the 8".

You want to draw me up some plans to install a single-phase? 110 would give you extra brownie points.

Do you have a source for a 110v motor of that size? You're looking at about a 1AWG wire to run that many amps. How does the motor couple to the saw?

Beau Davidson wrote:

Mike Haasl wrote:I afraid I think this has comedy (in the Paul sense of the word) and lots of fuckery written all over it.  Not knowing much about big honking motors, I'd see if a single phase motor could be put in instead.  Or go with the 6" model which would require much less power than the 8".

You want to draw me up some plans to install a single-phase? 110 would give you extra brownie points.

I will discourage a 110v motor.

It will use more amps and therefore bigger wires are needed.

Also when powered by an inverter, the inverter will run less efficient because the amps aren't even across the 240v.

Okay, Jeff, you think 240 is the way to go, up at the leviathan?  

jordan wrote:How does the motor couple to the saw?

I can get some more detail from turbosaw on this.  They said they could set it up for a motor of our choosing.

Beau Davidson wrote:Okay, Jeff, you think 240 is the way to go, up at the leviathan?  

Either at the leviathan or the new battery cart (can be brought down to basecamp to charge at night) that Paul is having me build.

What voltage has your solar system?

I would try to find a variable frequency drive that works directly from the battery and generates the 3 phases for the motor.
That also avoids the startup problem, as it is designed to drive a motor.

Some thoughts from a been-there done-that corner:

You can buy or make a rotary 3-phase converter. I made one by using a 10 HP 3-phase motor driven by 240V single phase power to one of the windings. There's a big start capacitor that I manually engage to get it spinning, then bypass as the motor comes up to speed. The 240V mains is passed through to the load motor and the other two phases are generated by the idling motor, albeit at reduced voltage (about 200V) and imperfect phase angle. It's good enough to run a load up to 5 HP, provided that it starts unencumbered (so no pumps or heavy machinery to get moving, but fine for a saw where you get it up to speed before cutting). It's been working for at least 25 years and I used it this morning.

There are also solid state converters, but they are monstrously expensive and lossy. Definitely not something you want on a solar array.

Why even bother with 3-phase AC? Because the equivalent motor power can be developed by a much smaller frame, the power factor is superior (less heat), the design is far simpler and more robust (no brushes), they're self starting (no capacitors) and you can reverse the direction of rotation just by swapping two phases with a switch. It's the most cost-effective way to turn spinning motion into alternating current, and vice versa.

However, setting up a 3-phase photovoltaic rig is almost three times as complicated as a standard one. Three equal-sized banks of panels need to be to matched to the inverter and you can't let one of them get derated by differing angles, dirt, or shading. Same goes for batteries: three banks, matched and maintained for balanced output. So there actually is a use case for using solar to generate a big slug of single-phase AC power and then use a rotary converter to feed it to your grunty motors.

i built a rotary  converter, to run a 3phase pillar drill, i did not design it --that wizardry was done for me by an old electrical engineer friend, but he insisted on using a 5 hp as the rotary  to power the 1.2 hp drill, as it was the only tool in the workshop on the converter. The rough rule of thumb being 3 to 1 needed as the surge of draw on start up is the problem and overheating , the more equipment running off the converter starts to balance the 3 phases out better as well ---as far as i could understand. So to start and run the single  existing 15 hp would need a large 45 /50(plus) hp as the rotary ---roughly speaking , i have an old 20hp 3phase motor and it needs a machine to lift it ---bloody heavy.Plus you would have to start that off your supply, lots of or big start capacitors (and run capacitors) ,of course thats all homebuilt , you can buy these as well and they would be better designed and to run.

I just called the guys from this video.  Their main rep for the US said that every electric swing blade mill in the market runs on 3 phase at this time.  They could build one without the motor as well if someone wants to tinker with it.

Mike Haasl wrote:I just called the guys from this video.  Their main rep for the US said that every electric swing blade mill in the market runs on 3 phase at this time.  They could build one without the motor as well if someone wants to tinker with it.

Now we have had the exact same conversation with this guy.

Oops, hopefully Jay didn't mind :)

It's not something I'm going to be able to tinker with, so I'm attempting to determine when I can select and source an appropriate motor and have them build the mill to accommodate it.  I think it's a long shot, but worth investigating, and I appreciate everyone's input.

My table saw uses a 3 hp 220 motor and runs a 10" blade through anything just fine.  These sawmills have much bigger blades (I think 15" to do a 6" cut?) and a fatter kerf.  But it does seem like this is doable.

Are 3 phase motors cheaper and that's why they only supply them?  Or are there other benefits to 3 phase that we'd be missing out on?

It feels like a 10+ hp motor should be able to do the job if it can be mounted in there.  

Maybe buying an electric sawmill without the motor would be an easier conversion than buying a gas one without a motor.  

OK, I am really going out in left field with this because I was a special case.  And I am pretty sure you are committed to solar.  I commented in my earlier post about bringing in commercial 3 phase.  That was in the late 80s.  I did it for “free”.   I contacted a beer company that was willing to pay for the lines to be brought in IF I agreed to do aluminum can recycling and IF I was willing to have a semi trailer parked on my property with their logo on it to receive those cans.  When the contract ran out, the trailer and recycling equipment vanished and I kept the 3 phase.

The ideas above are great with a clean power source. Unfortunately a so-called "pure sine wave inverter" is still an assembly of chopped up voltages, just with much smaller slices to form something that sort of resembles a sine wave. The two latest videos from Matthias Wandel's second channel go fairly deep in to this and specifically how it reacts to large inductive loads.





On top of that, you want to minimize any runs of wire, particularly before it has been converted to 3-phase. Merely calculating ampacity for conductors as if it was powered by the grid won't account for system voltage drop (as opposed to wire voltage drop), and even tiny fractions of an ohm more resistance will make a tremendous difference. Just the wiring and connectors of using multiple pieces of equipment to try to convert that much power is going to cause problems, and the most likely case will be something melting or otherwise being destroyed.

I think the best bet to avoid such a meltdown would be to find a commercial company that sells 3-phase solar inverters, and to get it as close as you physically can to the batteries to minimize voltage drop. Oversized conductors with solid connections that are cleaned up before assembly (no matter how shiny beforehand) will help avoid problems. Efficiency is important, but it's meaningless if something melts down and never works. I don't know if a single phase inverter would survive powering a Variable Frequency Drive, or if the inverter-powered VFD would survive powering the motor, particularly at startup. I would imagine a company supplying a 3-phase solar inverter would want to know all of the specs for your motor and would be able to provide something suitable. It won't be cheap, but cobbling together parts that end up destroying themselves or catching fire would be dangerous and a waste of resources.

Never gonna fly, Orville.

Dan Fish wrote:Never gonna fly, Orville.

Which idea won't fly?  Or do you mean none of them will fly?

@Mike, the main reason I would give for using 3-phase to power the sawmill is illustrated in the photo in your post. Look at the size of the motor and how there's just enough clearance for the beam. A similar rated single phase motor would be much bigger and simply wouldn't fit in the application.

I forgot to mention the very relevant bits that @Tony cited: sizing for startup current and the smoothing effect of multiple small motors on the 3-phase network. And @Daniel's caution about "sine wave" inverters is well advised. Inductive loads are not digital friendly.

Thinking a little outside the box...if you're milling shedloads of timber, you could feed the offcuts and sawdust into a rocket boiler and run a steam turbine to generate your juice. Wood has about 5 kWh/kg thermal energy, and with a decent setup you could get 75% conversion efficiency to electricity (maybe even better given the performance of rocket combustion)

Phil, if we were going to go to the effort of building a converter like you describe, what would be the power consumption and loss?

Do you have any resources on the process of getting the specs right and basic construction and implementation?

Tony's advice is as about as good as I could give. You want your converter motor to be 2-3x the rating of the load. Keep the wiring runs as short as possible on the single-phase side of the system. Consider a smaller idler to have going on the 3-phase side to smooth things out. Get a qualified electrician to give it the once over and hook things up.

DIY how-to

The power loss for commercial RPCs is typically around 100-150 W per KVA and is highest at idle. For a rule of thumb, call it 10% worst case but more like 5% when you're working.

Commercial product FAQ

after seeing that clip ,now i want one of those , to add further complication to my already lengthy projects to do list, so anyone know the biggest horsepower electric motor that could be run on single phase , or in this case off the inverter ? Plus i am now starting to think of woodgas powered generator, too much ,too many distractions on this damn site, but i do hope some solution comes around

Sort of just a joke really, but I am just thinking that we aren't gonna see a single phase swing blade sawmill. I don't think it's impossible per say, just out of the reach of normal joes. I am wrong ALL THE TIME though...

My money says it would be easier to use the solar to fill a large pond with water and then build an old school water powered mill.

tony uljee wrote:Plus i am now starting to think of woodgas powered generator

This is exactly what I was thinking. It might be easier and cheaper to build a wood gasifier to convert an engine powered sawmill to something a bit more sustainable. Or find a wrecked electric vehicle with functioning motor/controller/battery. Perhaps even get one of the Sur-Ron ebike motor kits. It looks like they have some seriously powerful options with wide voltage input. Technically the BLDC motors are 3-phase motors just wound differently than grid powered motors. If you could get it to output enough power at an appropriate RPM then it might be a good option. I don't know all the specs to the Solar Leviathan, but it could perhaps be reconfigured for higher voltage, or at least used to charge a separate battery pack.

This is more or less the plan I wanted to work on this year. I was going to try to make a chainsaw mill powered by an ebike kit and solar panels. I could at least get slabs roughly cut and finish with a tablesaw. Of course then I would want a solar powered tablesaw, but I could worry about that while the slabs are drying. I've already got a couple old chainsaws and plenty of battery power, so it's in the realm of possibility.

There are several all-in-one inverter solar controllers that can be Daisy chained to do three phase. It will take three of them, but not really any more expensive than a three phase converter and WAY better.

I would go with a slightly different rotary converter.

If you've got access to the battery system, then I would skip the single phase - inverter setup and run the 3phase motor-generator from a dc motor from a fork lift or milk float.

I would install the dc to 3 phase rotary converter as close as possible to the battery bank and then run 3 phase out to your workspace, as the higher voltage/lower current of the 3 phase line will reduce power losses.