iDRY Vacuum Kilns

Sponsors:

Thinking of customizing new mill to be electric driven

Started by Logginsteve, October 01, 2011, 06:33:36 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Logginsteve

Hi all,

I'm in the process of setting up for a Spring 2012 sawmill construction project.  After a TON of thought and consideration of pros/cons, the new mill will be stationary 100% of the time.  I'll get to bugging you guys for advice on layout a bit later :), but for now some questions about the mill itself.

I'm going to be getting a 24" bandsaw that comes standard with a 11hp Honda gas engine, which I'm thinking of substituting with a 7.5hp 3 phase general purpose motor.  I've identified a Dayton 2MXU9 as having the correct RPM, dust resistant housing, and capability of running off of VFD.  Since I only have single phase I'd get a VFD for single to 3 phase, which takes care of the power supply problem as well as getting the benefits of variable speed.  I've found many VFDs that will do the trick, but haven't checked into which is the best bang for the buck. 

I want to do this because I hate small engine maintenance, want to have the mill very close to my house (electric = quiet), and over a very short period of time it will be a lot less expensive to run and maintain.  Since I'm not going to move it at all, and need to wire the mill building for juice anyway, it seems like a very sensible thing to do.

Technically I should be getting a 7.7hp motor, as that is the correct substitute for the 11hp gas, but the next step up is 10hp and that complicates the VFD and increases the cost significantly.  Plus, it's overkill.  I'm thinking that at 7.5hp, with the benefits of variable speed and consistent torque, I think I'll be fine for the species I deal with (I live in Maine, so very dense woods aren't an issue for me).

For other stuff I intend on putting a power cutoff on the travel head and a dedicated breaker box.  I'll kill the breaker when I'm done for the day.  A drum throttle (with reverse blocked off!!) should do the trick for speed control.  Dayton makes such a controller for 5hp motors so I'll just go with that since I know it will work.  Apparently I have to put the controller between the single phase and the VFD, but I'm not 100% sure about that.  I'll consider it a bonus if any of you are a circuithead on the side and can help me out with VFD stuff.

Hmm... that's about it.  I think!

Thanks,

Steve

Larry

I know a little about VFD's.  There should be nothing but wire between the VFD and the motor.  You can smoke one quite easily if the motor is powered and the circuit interrupted by a switch or plug.  To control the motor...speed, reversing, on/off, there are low voltage circuits to accomplish it.

When you get above 3 hp with a VFD most will have to be derated by some factor to work on single phase.  Some will automatically check for phase loss and shut down.  Check with the manufacture.  50% derating is common and that would mean a 15 hp VFD for your 7 1/2 hp motor.  Really big bucks. 

I would build, buy, or borrow a rotary phase converter and pick up a 10 to 15 hp motor for the sawmill.  I usually pay around 5 bucks a hp or less.  Bout the only thing to go wrong with a 3 phase motor is the bearings and there easy/cheap to change out.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Logginsteve

Hi Larry!

Thanks for the thoughts.  I didn't understand the derating bit before, but now do.  Some questions for you:

1.  I'm confused by the "big buck" comment.  For under $700 I found a new 15hp VFD that seems to fit what I need.

2.  I know I can go single phase for less $$$, however I lose all the advantages that come with VFD.  Specifically, more efficient and responsive speed control.  Though I don't know how important that really is in this application (vs. a CNC, for example).  Is there a reason that VFD would be a waste for sawmilling?

3.  Where can I find quality motors for $5 p/hp?

4.  I only need 7.5hp to match what the sawmill is designed to handle, so why do you suggest as much as 15 hp?

Sounds like I read correctly that the throttle has to be inbetween the single phase and the VFD.  Makes perfect sense to me this is a requirement. 

Thanks!!

Steve

bandmiller2

Steve,I converted my home built bandmill from 16hp gas to 20hp 3 phase best thing I ever did scads of power and easy to start.You don't need VFD on your bandmill it will just complicate things and cost you bucks.Put a 10hp single phase motor on the band drive and smaller motor to run the hydraulic pump for the feed and log turners.Figure your band speed and select motor RPM and sheves to get you there then forget about it no need to keep changing.Keep us posted Steve. Frank C. [the simpler something is, the better]
A man armed with common sense is packing a big piece

bandmiller2

Steve,I converted my home built bandmill from 16hp gas to 20hp 3 phase best thing I ever did scads of power and easy to start.You don't need VFD on your bandmill it will just complicate things and cost you bucks.Put a 10hp single phase motor on the band drive and smaller motor to run the hydraulic pump for the feed and log turners.Figure your band speed and select motor RPM and sheves to get you there then forget about it no need to keep changing.Keep us posted Steve. Frank C. [the simpler something is, the better]
A man armed with common sense is packing a big piece

Larry

They've come down in price some since I've looked.  Still $700 is a significant investment to power one motor only.  I can't see any advantage to speed control on a sawmill.  I have a VFD on a 20" shop bandsaw.  I seldom vary the speed on wood but do slow down to saw non-ferrous metals.  Braking is a nice feature.

Re-sale on 3 phase motors is near junk price.  Industry buys new and most people do not have access to 3 phase.  You will just have to go prospecting, mostly at auctions.  Single phase motors in your hp range are quite scarce and the cost goes way up.

I feel more hp is better, especially if it comes with a small cost.

I always thought a VFD with a small gear motor would be great for making power feed but I don't know if its been done.

The throttle is not really between the single phase and VFD.  Its a pot (some are built in) that controls the VFD through a low voltage port.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Magicman

Quote from: Logginsteve on October 01, 2011, 06:33:36 PM
  as well as getting the benefits of variable speed. Steve 

I can not think of any benefit or use for variable speed.
Knothole Sawmill, LLC     '98 Wood-Mizer LT40SuperHydraulic   WM Million BF Club Member   WM Pro Sawyer Network

It's Weird being the Same Age as Old People

Never allow your "need" to make money to exceed your "desire" to provide quality service.....The Magicman

Woodwalker

Quote from: Larry on October 02, 2011, 07:56:47 AM
I always thought a VFD with a small gear motor would be great for making power feed but I don't know if its been done.
I've got a VFD running a three-phase motor thru gear reduction  on my travel. Works great. Variable speed in the cut and gig back at speed. There are a few pictures in my gallery.
Just cause your head's pointed, don't mean you are sharp.

Logginsteve

Fantastic responses!  Thanks for once again reminding me why this forum is such an asset for newbies like me.

OK, looks like the perceived benefits of VFD are, in this application, largely unnecessary.  Larry confirmed a nagging suspicion I had about the speed that on/off is good enough most of the time nearly all the time.  The pricetag for a VFD doesn't bother me, though, as over the lifetime it will come out to be much cheaper than a gas based system.  But I don't like wasting an opportunity for better savings!

Therefore, #1 option is to get a rotary inverter (probably won't make one myself, but maybe...) and a used 3ph motor.  I know a place that sells reconditioned industrial motors so there's at least one place to start.  I will remain flexible on the HP and instead concentrate on getting the RPMs in the right ballpark for this particular mill (3600).  7.5 to 15 hp is the range, which isn't that expensive if I wind up going new.

However, this now begs the point bandmiller2 touched on.  For something in the 10hp range, fixed speed, is single phase a good option?  Obviously that would be the most simple, straight forward, least expensive way to go.  Even with a brand new motor.

Thanks again for your collective help!

Steve

logwalker

I think you are going to have to rethink the VFD. It will only give you a percentage of the rated power of the motor. And to be realistic, 7.5 hp electric is not much in big cut. I have several 7.5 hp motors in table saws, a vertical bandsaw, and 22" radial arm. I run my WM LT40 with a 15 hp electric off a 20 hp rotary that I found on Craigslist for $500. I wouldn't want any less power than that provides. Your 7.5 hp off a VFD may only give you 5 true hp.

So I would suggest you at least go rotary converter and at least a 10 hp motor. That will also give you the advantage of adding other low cost machines to your saw shed. I am buying 3-phase tools for pennies on the dollar because they are 3-phase.  

You do need a 100 amp service to run a 20hp rotary and the downstream tools. Something to consider.

Joe                                                                                                                      
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

Magicman

What is the weight difference when converting from gas to electric?
Knothole Sawmill, LLC     '98 Wood-Mizer LT40SuperHydraulic   WM Million BF Club Member   WM Pro Sawyer Network

It's Weird being the Same Age as Old People

Never allow your "need" to make money to exceed your "desire" to provide quality service.....The Magicman

pineywoods

Steve, if you are considering converting an existing gas-powered mill to electric, don't overlook the weight difference. I doubt you 12 hp gasser weighs 100 pounds. A comparable powered electric will weigh 2 to 3 times that. Will your existing head support and head lift support that ? Likewise, instead of a single phase motor, you will probably find you can acquire a rotary converter and a 3 phase motor for less money. Then you have the option of using other 3 phase equipment. There is a local mill (WM LT40) that was converted from a gas onan to 3 phase electric. The head lift mechanism wouldn't bulge the electric. He mounted pulleys on the top of both masts, ran cables over the pulleys and down to the head. The other ends of the cables have over 200 pounds of lead weights attached.
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
100k bd ft club.Charter member of The Grumpy old Men

Logginsteve

Shipping weight of the standard Honda is 90 pounds.  Shipping weight of one model of 10hp 3ph I found is 170 pounds.  A significant weight increase, but it should be doable as the head is raised/lowered using roller chain.  Perhaps with some reinforcement of the head frame it will be fine.  I can find that out if everything else looks to be a go.

I do have a 3 phase welder sitting around, but I'm not sure if a 20hp rotary inverter will handle it, nor am I sure I can rig the wiring so I can have each in the location I want.  But that's another bridge to cross later on ;)

Joe, good point about what my power feed has in terms of amps.  I guess I'm getting to the point where I should figure that out.  If the grid isn't putting out enough juice to feed a rotary inverter then this whole discussion becomes moot.

Thanks,

Steve

Logginsteve

I'm dusting off my old thread here because I need to put in my sawmill order and I've still not decided about going with electric or gas.  I called Thomas Band Sawmills (for sure I am going with their 30" model, not 24") and talked with them about a conversion.  They've definitely got customers who have electrified theirs, buying without the Honda engine, but they themselves have not done any conversion work.  Hopefully some of you out there with experience can help me make up my mind:

1.  VFD is out as an option, thanks to the above discussion.  But is single phase 13hp equivalent a good way to go?  That way I won't have to mess with a rotary convertor and allow myself (theoretically) the option of running off a generator.  Which brings me to...

2.  Anybody try running their mill off a generator?  I'd hate to eliminate the possibility of moving this thing to a remote location simply because I don't have a backup power source.

3.  I'm interested in recommendations for motors and any related bits I might need.  Are there any other components I'm not keeping in mind?  Power disconnect, for example?

Thanks,

Steve


Magic Smoke

Use a single-phase motor, it easier, less complex, and cheaper in the long run than running a 3-phase with a phase converter. You're going to pretty much max out at 10HP though with 1-phase, look at 3-phase if you need more HP.

Newer generators with the electronic governors work okay in a saw applications as long as the generator is sized appropriately to handle the loads. The older generators don't respond quick enough to loads in a saw applications and can cause sags in the supply (never good).

Logginsteve

The mill comes with a 13 HP which runs at 3600 rpm (I think, need to double check).  In theory this means I need a 7.8 HP electric motor with similar rpm.  Bump it up a bit just to be on the safe side, but it looks like I won't go over the magical 10 HP number.  Man they get heavy after that!

Steve

JFarmer

I converted my LT40 from a 33hp kubota to a 25hp electric. I have never regretted it!
LT40 electric,woodmizer twin blade edger,cooks catclaw sharpener,suffolk setter, john deere 450 dozer, case 90xt skidsteer, 7010 4x4 mahindra tractor

Slabs

Dayton also has a 10 hp single phase that would eliminate the phase converter and the respective losses.
Slabs  : Offloader, slab and sawdust Mexican, mill mechanic and electrician, general flunky.  Woodshop, metal woorking shop and electronics shop.

Woodwalker

Check with your electrical provider before you go and buy a large single phase motor. Depending on several factors that involve existing line load, voltage drop\sag, number of neighbors feeding off that line\transformer there may be some restrictions on what you will be allowed to run. 10HP and above single phase motors upon starting draw a lot of amps.
Just cause your head's pointed, don't mean you are sharp.

bandmiller2

Alas,theirs much I don't know about electrics,would soft start and/or power factor correction help on large single phase startup?? Frank C.
A man armed with common sense is packing a big piece

Hilltop366

If starting up was the only thing holding you back from going 10hp single phase I am wondering if a smaller motor could be used to get things turning up to speed then turn on main motor.

Would this work? I'm not sure, someone else on here may be able to say.

If it would it should be easy to gear up by putting the small motor on a pivot and pushing it's pulley on the drive belt until things are turning.

A smaller motor from a broken washer or compressor should be easy to come by cheap I would think.

sparky

Steve,
I just came across this tread and would like to make some comments about VFDs. I am a retired electrical engineer and installed hundreds of VFDs in my career. Later this week, I will be assisting a friend with the installation of a 30 hp VFD on a 10 HP load. I bought this VFD for $300, new, thru a local on-line auction. I should have bought more!

A VFD needs to be derated 50% to produce 3 phase power from a single phase source. One member of FF suggested you talk to your power company to see if there are any constraints with running a large motor on your service. A VFD will provide you with reduced inrush current when starting if that is a requirement. Power factor correction capacitors serve the purpose of reducing voltage drop when long lengths of electrical service are involved.

Electric motors are rated with a service factor that allows for overloads for a short time. A service factor of 1.25 allows the motor to run at 125% of its rating, for instance. This would allow a motor in a sawmill application to load up when making a heavy cut as the work is not continuous.

Single phase motors are more complex, and much more expensive, than 3-phase motors. Single phase motors have centrifugal switches, starting windings, and capacitors that are all failure modes. I worked in a motor shop for short time, and the repair of single phase motors was a source of steady work. A 3-phase motor is also more efficient. The efficiency of 3-phase motors is consistent from 50% to 100% of their rated HP. This would allow you to buy a larger motor if the price was right and the VFD could support it. A larger motor would provide the HP you mill may need on a tough job.

I am not a fan of phase converters since they reduce system efficiency and they do not produce balanced voltages or currents. I spent hours trying to balance the capacitors in a phase converter to keep a motor from overheating and found it impossible. They have applications, but a person needs to know of their limitations.

Sparky
I'tnl 2050 with Prentrice 110, Custom built 48" left-hand circular and 52" Bellsaw right-hand circular mills, Jonsered 2171, Stihl 084, and too many other chainsaws. John Deere 3020 and Oliver 1800 with FELs. 20" 4-sided planer and misc.

Woodchuck53

Sparky would a CNC rated machine balance all 3 legs? I have started specing out a larger 3 phase rotary converter for a dual, 10 hp air compressor set up. I will also use it on a 12 hp 21" non CNC lathe. I have a misc. collection of other 3 phase tools but am really only concerned with enough power for the air comp at this time. I am trying to get away from the up keep and noise of the diesel unit I use now when I sand blast.

Would you be willing to help seperator the grain from the chafe on what's out there? Right now it has been recommended that I go 40hp on the converter????

Chuck
Case 1030 w/ Ford FEL, NH 3930 w/Ford FEL, Ford 801 backhoe/loader, TMC 4000# forklift, Stihl 090G-60" bar, 039AV, and 038, Corley 52" circle saw, 15" AMT planer Corley edger, F-350 1 ton, Ford 8000, 20' deck for loader and hauling, F-800 40' bucket truck, C60 Chevy 6 yd. dump truck.

bandmiller2

Chuck,running that much off a single phase line is a tall order,let alone the conversion losses.Prehaps you'd be better off with a large surplus 3 ph. generator in its own sound reducing shed and run your whole complex with it,sawmill included.Air comp. are probibly the most demanding electric load.Phase converters are at their best running shop machine tools. Frank C.
A man armed with common sense is packing a big piece

Larry

Quote from: sparky on February 26, 2012, 10:18:31 PM
Single phase motors are more complex, and much more expensive, than 3-phase motors. Single phase motors have centrifugal switches, starting windings, and capacitors that are all failure modes.

Yes, but you have moved all the complexity and increased it ten fold into the VFD.  The up front cost has increased along with maintenance expense.  And when it breaks do you take to the local VFD repair shop?  In most cases, the single phase motor is an easy fix when broke, and they go a long time between break downs in a home environment.

A big fan of VFD's but also in touch with the cost.

I've balanced RFC's quite successful for one specific motor load but maybe I was lucky.  I've heard of problems, especially when using a foreign made motor.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Al_Smith

I've had very good luck with building rotary converters .As rule on 240 volts the capacitance is 7.5 MF per HP for the run cap .Below line voltage you add capacitance and above  you decrease .

It's always been a point of arguement or discussion as to the cost effectiveness of rotarys but truth be known properly built they are in the neighborhood of 92 percent .

As an example a 10 HP rotary will start up that size of motor and run up to 3 times that amount of multiple motors or in this case 30HP .

Under load as generating the third leg of three phase they draw about 1/2 the running current of the motor or as a 10HP that would be around 12-14 amps .25 amps would be about the load of a 10 HP as use perhaps as power for a mill .Giving around 40 more or less as the combined load  on the single phase line .

Now of course this is just one mans opinion on things but a three phase motor is certainly more trouble proof than single phase .It has a much higher starting torque and used they are pennys on the dollar compaired to a large single phase motor .

They have no start switch to arc and spark .As been already stated about the only thing to go wrong with them is the bearings which last almost forever .

FWIW VFD drives are costly and inefficient .If you don't have the correct type induction motor in use with a VFD it will not last long .Besides all that there really is no reason a person would need to have speed control on a sawmill that I can think of .Set the drive pulley size and call it a day .

Woodchuck53

Evening Frank, How are you? Well all this is still in the thinking stage and I welcome all arguments for or against. The 7.5 that is on my small lathe and grinder are fine and would add the end mill to it as soon as I get around to wiring it. It's the dual air compressor that is worrying me. All are right the swapp to a pair of single phase motors will really hurt the budget at this time. I will eventually have to bite the bullet and do something as the old diesel air compressor is not totally owned by me.

As for now my blasting and painting has been small potatos and all my own needs. But I am still thinking of my future plans and am leaning toward a good Temco unit big enough to handle it all.

I wish I had enough money to bite the bullet and bring 3 phase into the shop and mill.
But we will see. Thanks again. Chuck
Case 1030 w/ Ford FEL, NH 3930 w/Ford FEL, Ford 801 backhoe/loader, TMC 4000# forklift, Stihl 090G-60" bar, 039AV, and 038, Corley 52" circle saw, 15" AMT planer Corley edger, F-350 1 ton, Ford 8000, 20' deck for loader and hauling, F-800 40' bucket truck, C60 Chevy 6 yd. dump truck.

Logginsteve

Good discussion, thanks!

I spoke with a middle manager at my power provider.  He is waiting for me to send him specific specs so an engineer familiar with my line can make an informed opinion about viability.

I've run into the rotary convertor + 3Ph motor vs. 1ph motor debate in other forums while doing research.  It seems, like so many things, that there are pros and cons to each.  Not surprisingly those pros and cons vary depending on what the planned use is.

From what I've seen, it seems that if the only thing I plan on running 3Ph is the mill, then it probably makes sense to stick with a 1Ph motor.  The argument for this is simplicity, lower starting cost, and low probability of practical problems down the road that exceed the rotary/3Ph combo.  Now, if I was in need of running more 3Ph motors... seems to me that the argument swings back over to favor a rotary convertor because you're leveraging that investment against the savings of several applications.

BTW, I have once again changed my mind and am going with a slightly smaller mill.  This means I only need a 7.5HP electric motor to replace the 11HP gas motor.  The specs I need to match are:

The Honda 389cc GX390 Series
Net Power Output: 11.7 HP (8.7 kW) at 3,600 rpm.
Net Torque: 19.5-pound-Feet (26.4 Nm) at 2,500 rpm.
PTO shaft rotation counterclockwise (from PTO shaft side).

I have to look again at motor options, but it wasn't hard to find the right HP and RPM.  What I have had trouble finding (easily) are the torque ratings.  Obviously very important for a sawmill.

Oh, and I was already steered clear of VFDs in a couple of places.  For a sawmill application it seems a no brainer bad idea.

Steve



Woodchuck53

Morning all. Well I did it this past hitch home. I found a used Temco 50 hp in Freeport, Texas. Fellow brought it up and met me at a motor shop. We wired it in and spun it over and it runs nice and quiet. This model has 2 50 hp idler motors and 2 seperate panels on the same skid package. We set an inline switch and hooked up a 50 hp motor from stock and spun that up. I noticed no draw down or noise from any thing so i paid him off and took it home. I hope to wire it in to my shop this trip in and power up the lathes and big air compressor.

I think this will do for me now and maybe later bring in the power from the front utilities. Will get pictures and post the set up as soon as I can. Any other particulars some one wants to know can pm me later. Stay safe.
Case 1030 w/ Ford FEL, NH 3930 w/Ford FEL, Ford 801 backhoe/loader, TMC 4000# forklift, Stihl 090G-60" bar, 039AV, and 038, Corley 52" circle saw, 15" AMT planer Corley edger, F-350 1 ton, Ford 8000, 20' deck for loader and hauling, F-800 40' bucket truck, C60 Chevy 6 yd. dump truck.

bandmiller2

Chuck keep us posted how it works out,would be kinda nice to have a little friction brake on the electric meter. Frank C.
A man armed with common sense is packing a big piece

Thank You Sponsors!