DC powered Band Saws

Discussion in 'Shop Talk' started by stephenkane, Jan 4, 2005.

  1. stephenkane

    stephenkane New Member

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    I am beginning research for a saw mill I'd like to purchase. I am planning on powering this mill with micro hydro power and would like to use the DC output and not add an inverter to the mix. Does anyone know if Linn or some other band saw manufacturer makes a DC power saw?

    Thanks in advance for the assistance.


    Stephen
     
  2. WanderingOak

    WanderingOak Well-Known Member

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    I do not know of any band saw manufacturers off the top of my head. However, I do know that DC works best over short distances. Unless your saw is going to be very close to the hydro plant, you are going to have quite a bit of power loss over the transmission line.
     

  3. fordy

    fordy Well-Known Member

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    ...............Depending on the lineal distance between the water genset and the bandsaw location you will encounter the same Losses or drop in DC voltage that all transmission lines encounter when endeavoring to use DC as opposed to AC . That is why virtually ALL power lines use AC current as opposed to DC . Better to use an AC generator and rectify\convert it to DC at the bandsaw location than try to run pure DC all the way . Also , when you take 12 , 24 , or 48 volts DC and invert IT up to either 120\240 vac the Laws of "Economy of Scale" apply . If , your DC voltage to the inverter is 40 vdc and your load needs 120 VAC you have a Conversion factor there of 3 : 1. Which means , ignoring the losses in the Inverter that you will probably have to generate 3 amps of DC current to create 1 amp of AC current . This is very INefficient in electricial terms . That is the reason that ....the Ac voltage on most power lines to residential neighborhoods are like 14,000 volts ac . There , they are converting ....DOWN to 120\240 volts AC . That is the reason that one , single phase power line can efficiently supply power to numerous homes(loads) ...fordy.. :)
     
  4. stephenkane

    stephenkane New Member

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    I am aware of all of the limitations of transmitting DC power. The linear distance from Battery Bank/MicroHydro is less than 100 feet. The purpose of putting in this saw at this location is so we can run it DC. That way we avoid all of the losses through the inverter. Also, DC motors are more efficient (what calls for a 1HP AC motor can be acomplished with a 3/4 or even 1/2 HP DC motor). I work as a Renewable Energy Tech so I know this CAN be done, I just haven't found a band saw that is run by a DC motor yet. It might be as simple as getting a LINN and finding a DC motor to run it.

    Thanks for all the info though.

    Stephen
     
  5. Ed Norman

    Ed Norman Well-Known Member

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    Can you drive it with a water wheel and skip the slectricity?
     
  6. John Hill

    John Hill Grand Master

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    I am wondering why it would not be better to put an alternator rather than DC generator at the Hydro? At least with AC you can transform it up and down to reduce the line current without getting into to serious money.

    I am not sure what you mean by the DC motor compared to the AC motor, are you thinking of the superior starting torque of the DC motor? In your situation wont that just stall the hydro?

    Wouldnt the best system of all be a 3 phase alternator and 3 phase motor? I have seen various schemes for running a 3 phase motor as a 3 phase alternator but I really dont know how effective these lash ups are.

    Sorry, I know that was not the question you asked but it is an interesting subject.
     
  7. Cosmic

    Cosmic Well-Known Member

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    The simple solution is just buy your saw mill as a normal AC powered unit.

    Take your DC motor and drive an AC generator very close to the source or maybe even drive the AC generator directly with the hydro water power if possible. Whatever works best, speed control and all. Something like the one being sold by Harbor Freight 10KW generator system only for $299.

    http://www.harborfreight.com/

    Item # 45416-OBRA

    Probably the least complicated, maybe cheapest solution, plus you can use the AC generator power to other distributions too. Depending on how you lash it up can have both DC and AC power systems from the same prime mover.
     
  8. idahodave

    idahodave Well-Known Member

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    If you really want a DC powered saw I think you'll have to do it yourself...

    Check catalog #10-1690 at www.surpluscenter.com. Its a one horse
    12 vdc motor...only needs 90 amps, but probably draws alot less when
    free running

    If this is bigger than you need, look at 14 vdc battery powered tools, you might find something you could use and make a wire connection to the battery terminals
     
  9. Ross

    Ross Moderator Staff Member Supporter

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    If i can ever scrape together the money I want to make a hydraulic powered Linn sawmill. There are plenty of DC hydraulic power packs out there, and then you could add a power lift and turner.
     
  10. Blu3duk

    Blu3duk Well-Known Member

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    Ive run both gas powered sawmills and electric, been around the little bandmills when they were running in the same yard as my circle mill. From what i can see you need at least a 10 horse electric motor to power a bandmill for cutting lumber, The circle mills need a little more power cause they cut differently.

    I have a mobile dimension VW powered mill [1600 cc] 54 horse, they make an electric mill with 2 electric motors mounted one for the main saw blade and the other for the edger blades. I ran a homelbuilt circle mill with a 40 horse 3 phase on it and it was just about under powered for the really huge cuts like 8x12 in red fir even with the hydrostatic drive on it [my saw is mechanical drive]

    If you under power a bandsaw you will feed faster than the blade can stay at a constant speed and then you get blade drift [worse than normal under ideal conditions] ok so i wouldnt have a little bandsaw as my primary saw and i admit it from what ive witnessed first hand they just have too many problems and dont cut as fast as my circle mill nor as high of quality lumber. I understand there are a few people out in the world who may have a different story with their mill but ive looked hard at the various mills available and never found one of those thin blade band mills worth my time. And yes sometimes a band mill can recover a scant more lumber from a few logs, and sometimes they produce a board with less rough on it, but rough still needs planed, and 1x4's cost more than you can sell them for or use as firewood, and if you have dirty logs you spend more time sharpening blades than sawing lumber....

    That said, any mill made using a petroleum motor could be switched over to run electric providing a person could find a motor suitable to power it, and generating power frm a stream might not supply enough power when going any distance. Look into a Pelton type wheel, I understand that there are acfew on the market that can supply great amounts of power from smaller flows.

    William
     
  11. Don Selby

    Don Selby New Member

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    What KW can you generate with the Hydro GENSET ?
    Are you using battery back up/charging ?
    What Voltage output from GENSET??

    You could purchase band saw without electric motor.
    If it is a low voltage system I will be happy to help you
    select the correct DC Motor.

    OR, you may be able to get an old golf cart and remove
    the DC Motor and drive tarain.
     
  12. farminghandyman

    farminghandyman Well-Known Member Supporter

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    I may be wrong here but I was under the impression that DC was more efficient to transmit power with than AC, but the problem is to change the voltage, you have to invert it and then transform it and then rectify it to change the voltage in DC, and that is why it is not in general use,

    http://www.worldenergy.org/wec-geis/publications/default/tech_papers/17th_congress/2_2_13.asp

    http://www.wapa.gov/about/faqtrans.htm
     
  13. farminghandyman

    farminghandyman Well-Known Member Supporter

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    you would need a hydro plant capable of producing at a very min. of 5000 watts and preferable in the 10000 watt range, IF my figuring is correct,

    as you will be needing a 5 to 71/2 power motor in electric depending on model you choose,

    lest just say you use 24 volts, 5000 watt unit would be in the 208 amps,
    the 10000 watt would be pulling 400 amps, (expensive wire, and not very flexable)

    at 100 volts you would be looking at 50 amps or 100 amps

    but by the time you get the water wheel or turbine and the system set up the water head necessary the piping, the generator, the wiring, and the motor,

    I would think the gas motor that comes on them would start looking very good, for cost and portable and ease of use,

    and many of your DC motors are short duty motors, (cooling is not that good)