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Thread: VFD on old saw

  1. #1
    Join Date
    Sep 2007
    St. Louis, MO

    VFD on old saw

    A Powermatic 65 cabinet saw followed me home the other day. The rebuild is on the docket for this fall / winter (after i finish up the "summer" projects i'm not quite done with). I'm pretty excited about it. The contractor saw i've been using is a great tool, and i've done a lot of good work with it, but an old Powermatic cabinet saw was impossible to leave be.

    At any rate, it's got a 3 phase motor on it. Cheapskate bottom feeder that i am, i'm looking at my options for firing it up in my basement shop - steroid fed hampsters on a wheel, swap the motor for a single phase motor, or use a variable frequency drive (vfd). The motor is a C-frame, so that makes finding an old (read "cheap") replacement that i can rebuild and attach would require a stroke of good luck. Hampster roid rage is nothing i want to deal with, and phase converters have some serious downsides. So, i'm looking at getting a vfd to drive the 3 phase motor on single phase. This would be a lot cheaper than buying a new replacement motor.

    My hangup is that i've never used one before. What are the downsides? Anyone have an opinion? A 2hp vfd with phase conversion will run $144. That's about $200 less than a new replacement motor.

    Thanks in advance.

  2. #2
    Join Date
    Nov 2006
    Oak Harbor Washington on Whidbey Island
    Doesn't that saw usually run a 3 HP motor?

    My preference would be to save my money & buy a regular a single phase motor. You've waited this long save a few dollars & I presume your still only going to be a 1 saw shop, what can you get for your other saw & combine the cash with the sale of the saw & buy a motor.
    Last edited by Bart Leetch; 10-08-2010 at 10:07 PM.
    "Forget the flat stuff slap something on the spinny thing and lets go, we're burning daylight" Bart Leetch
    "If it ain't round you may be a knuckle dragger""Turners drag their nuckles too, they just do it at a higher RPM"Bart

  3. #3
    Join Date
    Oct 2006
    The Heart of Dixie
    Here is my two cents. I have done the VFD and no draw real drawbacks that I see. Well maybe one small one. VFD's don't like dust and vibration, at least the ones I worked with. So you need to keep it clean and maybe inside a box to keep the dust out. May mean you need to mount it off the machine somewhere. On my lathe I just mounted it on the wall, ran some wire from it to a remote box with on/off, speed control and reversing switches. Put a magnet on it and I could put it where ever I wanted on there On a lathe is it close to to the ultimate set up.

    Second option. Do you think you will ever buy a second 3 phase machine? You know they are cheap and often you buy a much heavier built machine for less money. So think about that. If the answer is yes then you should look into a phase converter. I ended up going that way and never regretted it. It took some time and a little money to build and run the proper wiring. But now I don't care if it is 3 phase. I have it in my shop. I have managed to acquire a couple of machines dirt cheap because they were 3 phase.

    My advice, one time purchase go with the VFD. If there is a chance of another 3 phase build a good rotary phase converter.
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  4. #4
    Join Date
    Jan 2009
    100 miles west of DFW, TX.


    Paul, this is 100$ more but I have experience with these drives.
    I work in a picture frame moulding manufacturing plant. Lots of dust! No problems with any of these drives or with Allen-Bradley vfd's. Being a bottom feeder myself, I've considered using one at the house and running several machines off of one drive.(only one machine running at a time!!).Check out this site

  5. #5
    Join Date
    Oct 2007
    N. Ga.
    I use vfd's in my shop for 3 phase power... but you should be aware that not all 3 phase motors are suitable for vfd's, has to do with the insulation on the motor windings and the AC wave form the vfd puts out. The life of a motor that is not "vfd rated" may be cut short. The other problem is you cannot use the motor starter on saw to start and stop the motor (without some serious rewiring). Given the start stop nature of a table saw you would have to use the remote control start/stop feature of the vfd. All that to say a rotary phase converter is a better option if you plan on buying more 3 phase equipment. If not, I would change out the motor and be done with it.

    A word of caution... if you are not comfortable around electricity or do not have an electrician friend, I would steer clear of both 3 phase options and change out the motor.


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