Three phaze converter

[ArborJake]

  Hello, Ive been reading along with you guys for a while and really enjoy the conversations and pictures of course. I have a Bellsaw circle mill with a 44" blade and powered by a three phaze converter and 40 hp electric motor. I just set it up this winter and have milled some Larch, White Pine and Norway Spruce. Seems to work pretty good I just dont know much about the power unit. Was wondering if anyone here has ever had or used a mill that ran on electric. Is the anyting special should I should know? I'll try to post a few pics.

  

  

 

[wood monger]

welcome to the forum arbor jake. I seem to remember someone on here who set up the phase shifter to run a 3 phase motor off of 2 phase power. I can't remember who it was but they'll probably be along sooner or later.

[Deere1981]

ArborJake
What amperage of service do you have feeding your phase converter?  I'm looking at setting a phase converter myself but have more questions than answers.  I'm needing it to run my ripsaw with a 50HP motor.
I'm also curious what you figure your power costs are per hour. 

[Al_Smith]

Rule of thumb on three phase 240 volt motors is 2.5 amps per horse power .The convertor loaded would be about half that .

They run in excess of 90 percent efficient  if they are designed properly ,92-93 or so .

40 HP with  the start up surge I'd guess of the top of my head 200 amps to start it .

A 40 is a pretty good size chunk of iron to get rolling ,the start up might be more than 200 .Then you'd need some type reduced voltage or compensater start circuitry .

So  if that would work and you could start on 200 you'd figure 100 amps for the motor plus 40 -50 for the converter .150 amps times 240 volts is the wattage times whatever you pay per killowatt hour ,8-10 cents .

At a dime per it would be around 3.50 per hour if it were a rotary  converter .

Now conversely if it was erroniousy named a converter but in essence is really a start circuit it allows to motor to run essentually as an open delta motor .As such it only produces about 60 percent of the name plate rating .

It would still draw 2.5 amps per HP but it wouldn't have the rotary converter load on it .

[ArborJake]

Deere1981, I actually blew the transformer the 2cnd time i ran the mill. The electric company sent a man out who told me basically the same as what Al said. They put up a bigger transformer and it's been fine since. Mine is hooked up through a double 100 amp breaker and once running seems to draw very little. I've not used it too much yet but my electric bill did not seem to go up much at all. Right now with diesle fuel costing over 4.50 a gallon in my area I think it'll be cheaper with the electric.

[bandmiller2]

Welcome Jake,very interesting mill power you have there.Do you think you could get by with A smaller motor or are you at rock bottom now.??From Al's figuring we can see the economy of even single phase electric,try to run any engine for $3.50 an hour. Frank C.

[bandmiller2]

Al, you mentioned a three phase motor running open delta is that the same a single phasing.Is that a valid way to use a three phase motor if you oversize it.?? Thanks Frank C.

[Magicman]

Welcome to the Forestry Forum, ArborJake.   

[thecfarm]

ArborJake,welcome to the forum. did you just get this mill? How are you getting the trees out of the woods? What's all the lumber going to be used for? And my last question for now,how long you been sawing?

[apm]

That's a real unusual setup for a Belsaw. Every one that I've ever seen drives the mandrel from the back side of the mill. Could you get some closer pictures of the actual drive system?

Greg

[Al_Smith]

Is that a valid way to use a three phase motor if you oversize it.?? Thanks Frank C.

It's an option if you build the circuit with a run capacitor in it .

If it doesn't incorperate a run cap the motor will overheat and cook it's self .You don't want to use something like this in a high starting torque situation such as an air compresser unless said compresser has a set of head unloaders .

The sell commercially so called "solid state " phase converters which are nothing more than a start circuit .On something like a small metal lathe they work fairly well because you generaly aren't using the lathes' drive motor at full capacity .

If a person is interested you can "Google " a hundred articles on the subject . An old coot ( my age )of a wizard electrical engineer put me onto it 35 years ago .This guy never had 1 day of college and when Ohio required a "P E " certification he "Grand fathered " it because he'd held the position for 40 years already .

He used to go around electrifying the old stripper oils wells in the area that had been running stationary engines which required a lot of maintainance .Bought the used motors for a buck a horsepower and the components from a military salvage place .Goes back years ,right after WW2.

[Al_Smith]

Another thing you have to remember is the power company will cheap out on the size of electrical circuitry .They figure every thing on demand factor which usually works for them .Every so often it bites them squarely in the buttocks then they take corrective action .

My shop for example I hung a monster of a service drop .250 MCM copper in 2.5 " conduit . They hit it with a number 4 aluminum .I questioned it .The lady said it would be okay .My reply was it's their transformer  not mine .With egg on face I must admit it's not been a problem so far .

[ArborJake]

I can get better pictures of the drive tomorrow. It is and older mill that must have run on belts becuase the wood block was still on the mandrel and there was a place for the shaft to drive the carriage cut out of the base. Now its converted to an hydrolic driven carriage. and yes I did just get it. The fella who owned it owned it for quite a long while and the three houses neighboring his are built from  lumber he made. Back when you could still frame a house with rough sawn. I am a tree climber and that's were I get moxt of the wood but also own 57 acres by my shop and 20 at my home. Mostly Red Pine, Hemlock. Some Sugar Maple, Ash and Cherry. Ive only just started miling. Turned alot of nice logs into firewood when no mill would take what they call a dooryard tree. I know many do contain metal but after 20 yrs taking down tree's you get a pretty good idea which ones will and wich might not. And there's also metal detectors.

[ArborJake]

 Oh yea,  I pick up wood with a custom made log truck I'll post pics when it comes back from the shop. I move wood around the yard and load the mill ramps with this thing. It's a hydro- max or as we call it the hydro crap. Its ugly but it'll lift a lot. 6 cyl onan engine that wont quit. Even when one of the guy's who works for me ran it out of oil till it shut right off. I let it cool down replaced one quart of oil with  some marvels mystery oil and it fired back up and has been running good ever since. The thing about the electric motor is it doesn't seem to dog down so if you feed to fast you'll just break the shear pins. should you go just slow enough that you donts shear them? I don't really have a clue. 

 

[Al_Smith]

Well the horsepower rating method is confusing dealing with gas or diesel in comparrison to electric .It's like at least double what a gas engine is maybe more .So that 40 is at least 80 were it gas .

I've had people argue it but facts are facts .

Now they lie about the ratings on small Chinese single phase motors as far as rating .That thing is a big old heavy duty industrial motor and if anything it's probabley old enough it's under rated .About the only thing that can ever go wrong with it is the bearings after 40-50 years maybe .

[ArborJake]

 I did actually check the bearings in the motor itself they shur looked new. What about the capaciters? I was told they not hard to find or replace. Oh and Al I have plans to build a horse barn or  Mule barn and then after that I'll try to sell the lumber. The locall farmer here wants to by the saw dust $50. a load. And Ive had people ask about slab wood. My first dozen board were 1/8 inch out at the back end, hence the name thick and thin.

[Deere1981]

Well the horsepower rating method is confusing dealing with gas or diesel in comparrison to electric .It's like at least double what a gas engine is maybe more .So that 40 is at least 80 were it gas .

I've had people argue it but facts are facts .

Now they lie about the ratings on small Chinese single phase motors as far as rating .That thing is a big old heavy duty industrial motor and if anything it's probabley old enough it's under rated .About the only thing that can ever go wrong with it is the bearings after 40-50 years maybe .

My electrician told me electric hp ratings are 3-4 times of diesel.  Agree?

[steve phillips]

to run a motor that size off single phase you will have to have an rotary phase converter . be sitting down when you see the prices

[Al_Smith]

You can buy a converter or make  one if you have the where with all . I suppose I've made 20-30 in my lifetime .The largest was a 30 HP .

As far as the  HP conversion  I was being conservative about double .What it actually is I'm not certain .

To get an idea perhaps looking at the Wood mizer electrics in comparrison to diesel powered on the larger units .

[thecfarm]

Nice building you have there.

[Larry]

I did actually check the bearings in the motor itself they shur looked new. What about the capaciters? I was told they not hard to find or replace.

I've never changed bearings on anything bigger than 20 hp but its an easy job.  Bearings are normally a low cost item.

Capacitors have a long life.  Surplus Center has a large selection as does McMaster Carr at higher cost.  The first place I check is always eBay...good place for bearings also.  A lot of times when a capacitor goes bad it will show physical signs.  Leaking, bulged case, or top blows off.

I've enjoyed the pictures of your operation.  Thanks for posting.

[bandmiller2]

Many times you can find large capacitors at the recycling areas in old air conditioners, I collect where ever I find them.An electric motor will take a large overload for a short time which makes them ideal to run sawmills because the saw is in the wood for short intivals.A steam engine and boiler is much the same.When a diesel electric locomotive starts moving a freight they will crank the engine up and 3 or 4 times the allowable amps for a short time to get the load moving then throttle back. Frank C.

[bandmiller2]

Al,sorry to keep asking so many questions,but you explain things so we/I can understand.No mystery with rotary converters built and have been using them in my shop for 40 yrs.Your open delta motor where do you put the run capacitor electrically,on the third unpowered leg??Do you keep checking the legs with an amp probe and adjusting cap. or is there a formula. Thanks so much. Frank C.

[ArborJake]

  Thanks every one for the input, it sounds like I did ok on the motor. I only paid $1500.00 for the whole thing and another $600.00 for work on the saw. I thought it wasn't too bad a deal. Thanks thecfarm, Me my father and my Uncle built it. Now ive got to add onto the other side to store what I kept in there.

[Al_Smith]

Your open delta motor where do you put the run capacitor electrically,on the third unpowered leg??Do you keep checking the legs with an amp probe and adjusting cap. or is there a formula. Thanks so much. Frank C.

It's the same as the start circuit for a rotary converter . You use maybe 1500 microfarad electrolytic to start say a ten H.P .and approx 7.5 M farad per HP oil caps for the runners on 240 volt .The runners are across the dummy leg and one hot leg .On 240 you want to keep the dummy below 300 volts .You decrease capacitance to lower the voltage and increase to increase .

The one in my shop is set to run 480 and the dummy is somewhere around 465 volts which is close enough .

What you have on the dummy is a lag because the circuit is inductive .The cap just brings it back closer in phase .

Someplace on here I've got pictures of a rotary but I can't find them .

Oh you guys that are looking for components ,check out Fair Radio ,Lima Ohio ,on the net .One of the largest and oldest electronic  salvage companies in the US if not the world . Good stuff cheap .

Let  me surf the net and find a wiring  diagram if I can.