How to replace unisaw motor
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  1. #1
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    Default How to replace unisaw motor

    Hey there i just bought a rockwell unisaw and it came with a 3 phase motor. I want to replace the motor with a 110 single phase 1.5hp and am having trouble finding one or use a vfd. I want to change the motor because i dont have three phase connection. Any ideas on options and can i use the three phase switch box that came with the saw with single phase? Thanks

    Motor specs:
    3 phase
    2hp
    575 volts
    3450 rpm
    145 frame
    60 cyc
    2.1 amp

    motor-060.jpgmotor-058.jpg
    Attached Thumbnails Attached Thumbnails motor-059.jpg  

  2. #2
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    You can find single phase 1.5hp motors in 110/220v, but you need heavier wire, short run, dedicated circuit, and you might squeak by without tripping breaker as startup amperage is too high, you would be better served running 220v 1ph.

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    You may be better off buying a VFD and using the existing motor. The Unisaw motors have a special mounting and don't have a standard motor base. Most likely there isnt much to choose from with their mount system.

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    Quote Originally Posted by peds View Post
    Hey there i just bought a rockwell unisaw and it came with a 3 phase motor. I want to replace the motor with a 110 single phase 1.5hp and am having trouble finding one or use a vfd. I want to change the motor because i dont have three phase connection. Any ideas on options and can i use the three phase switch box that came with the saw with single phase? Thanks

    Motor specs:
    3 phase
    2hp
    575 volts
    3450 rpm
    145 frame
    60 cyc
    2.1 amp

    motor-060.jpgmotor-058.jpg
    I have a new single phase direct replacement motor available, I can get the info over the weekend.

    Kevin

  6. #5
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    I made a mount for a 3hp motor for my old Unisaw. I used some big angle like 3x4 inch. I think I lost like 1/8" on cutting depth if any. You will have to replace the heaters in the overloads to run a 240 volt motor. You only need two heaters not all three. Or you can jump the heaters with solid wire and lose the overload safety effect.
    Before you get too involved check the coil to see if it is 240 volts or less. If it is 440 it is probably cheaper to ditch the switch gear and install a newer adjustable contactor inside the existing box.
    Other wise you will need two new heaters and one new coil.
    Bill D

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    My Unisaw is 1950's vintage. $10 at a local estate sale. It had the old bullet motor with the rare cast iron motor cover, 1 hp wired for 120V. Used it for years....until....

    Those old motors have what's sometimes called a "neck lace" spring that eventually breaks. The spring is part of the centrifugal staring mechanism. Motor will no longer run and replacements springs are not available. Local motor shop said they had not been able to get replacement springs for at least 20 years. The old wood working equipment site had a work around, but not a reliable one.

    New after market Unisaw motors are available, around $450 as I recall. Unwilling to spend that much I made a bracket to use a standard base-mount motor to tie into to the unique Unisaw motor attachment points. That worked fine except it lost some cutting depth and full 45 degree tilt because of interference issues with the too smallish motor clearance opening in the base. I was reluctant to cut the opening larger since this was an unmodified older saw complete with all accessories, somewhat collectible.

    After I re-engineered the motor mount I found Grizzly had the same bracket that was used in their Unisaw clones, less than a hundred bucks..

    Eventually I came across a used 2hp single phase Unisaw motor. I had to bite the bullet and cut the opening larger. I kept the cut piece so if the saw was ever restored with an original motor it could be welded back in.

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    If the motor is in good operating condition, I suggest you look at a VFD. It will probably be the cheapest and easiest way to get the saw running.

    Then go here:
    https://www.practicalmachinist.com/v...rters-and-vfd/

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    I run my 3 phase uni-saw via a static phase converter and it works perfectly. It uses the stock electrical components and was very simple and inexpensive to do.

    Stuart

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    Quote Originally Posted by peds View Post
    I want to replace the motor with a 110 single phase 1.5hp
    Do that and wait until you have a long 4x4 that needs a rip cut.
    A 3Hp 220v single phase motor is what the replacement should be.

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    I agree with the VFD as likely the most convenient and least expensive remedy overall, assuming you can find a match for the 575V operating voltage. Second choice would be direct replacement motor single-phase 220v version, but you will then be faced with mucking around with the contactor and heaters, to match all that stuff up. I would avoid down-rating the HP as a personal choice, just because you always need more guts in a table saw.

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    Thanks kevin

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    The mount that bill and doug made is it similiar to this one Alternate Motor Mounts for Your Unisaw - VintageMachinery.org Knowledge Base (Wiki) Would you mind posting pictures of your bracket with dimeensions and tips? Also What is a similiar or samller frame size for the 145 frame size that my motor has? Can the motor be smaller in size but have the same shaft size? Thanks

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    How could i test the motor with no 3 phase. And where is a good basic beginners place to start to learn how to wire a VFD if i was to go that way?

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    Are any of the Unisaws DIRECT DRIVE? Makes it quite a different task I suppose

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    There ought to be 240v single phase around

    That is what my Unisaw[1970s] is

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    Quote Originally Posted by peds View Post
    How could i test the motor with no 3 phase. And where is a good basic beginners place to start to learn how to wire a VFD if i was to go that way?
    There is a forum on this website devoted to phase converters and VFDs; lots of info there. And the typical VFD comes with lots of instructions.

    As far as testing a 3-phase motor with no 3-phase, the previous suggestion of using a static phase converter is something to look into, as well as using it as the poster suggested, to run the saw on an ongoing basis.

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    He said the original motor is 575v making it a poor candidate for a VFD (as best as I can understand, it is hard to change the input voltage with a VFD.

    Be wary that the older motors were slower speed with a larger pulley, so if you find one of those it may not match your pulley size.

    I like a 3hp minimum for ripping 8/4 hardwoods. But if you are not working such materials, you can probably get away with less.

    Pete

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    I think(? I dont think well) jets version uses a regular frame motor and a bracket. Might be worth a peek at a manual.

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    Man........a static phase converter is so cheap and so easy. The slight loss in HP will never be noticed on a hefty saw like a Delta. Hate to keep beating my drum but it really is a super simple answer to the OP's conundrum..unless I'm missing something obvious, which I've been known to do.

    Stuart

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    Quote Originally Posted by atomarc View Post
    Man........a static phase converter is so cheap and so easy. The slight loss in HP will never be noticed on a hefty saw like a Delta. Hate to keep beating my drum but it really is a super simple answer to the OP's conundrum..unless I'm missing something obvious, which I've been known to do.

    Stuart
    The fact that his existing motor is 575v MIGHT be the point you are over-looking........

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