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Thread: Unisaw motor help

  1. #16
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    Quote Originally Posted by Mike Kees View Post
    This is exactly why I really like three phase motors, so much simpler.
    Yeah, it makes the motors simpler, but increases the cost of the wiring and controls. Problems still happen, but usually in the wiring and control circuits and not in the motors. In factories, 3 phase motors that run nearly constantly are more efficient, so cheaper to run, but in a home shop the cost of a 3 phase installation is not justified by the lower operating costs. Now that phase conversion is more practical in small shops, these tools can be a bargain when bought used, but most of the time, installing 3 phase power from the power company to a home shop is usually not possible and frequently not at all practical.

    Charley

  2. #17
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    Quote Originally Posted by phillip kerrigan View Post
    OP here

    In case someone in the future stumbles across this thread and could also use some help with this problem, I found a video online that does a good job of explaining centrifugal switches as well as showing how to clean them:https://youtu.be/F-jOBxn1w1I. For someone who is not great with motors, I found it very helpfu
    Phillip,
    Thank you, thank you, thank you for posting this link. My Laguna dust collector had been down for over a month. Laguna's "assistance" ranged from BS to nothing. The guy your link lead to was intelligent, well informed and explained the centrifugal switch beautifully. Within 20 minutes my dust collector was back up running. You went beyond the norm of saying "thanks, it is fixed" and presented a solid approach to solving a real problem. Again, thank you! SMC rocks!

    Regards - Bill
    Last edited by Bill McNiel; 06-03-2021 at 11:16 PM.

  3. #18
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    Quote Originally Posted by Mike Kees View Post
    This is exactly why I really like three phase motors, so much simpler.
    That’s true, however the issue is the use of a centrifugal switch, both my Hammer machines bring the run and start windings to the starter panel.

    The start button has 2 contacts, one closes the latching run contactor, the other closes the non latching start contactor, once the machine is up to speed you release the start button.

    Everything is in the starter enclosure no need to access the motor, much smarter system....Rod

  4. #19
    Quote Originally Posted by Rod Sheridan View Post
    That’s true, however the issue is the use of a centrifugal switch, both my Hammer machines bring the run and start windings to the starter panel.

    The start button has 2 contacts, one closes the latching run contactor, the other closes the non latching start contactor, once the machine is up to speed you release the start button.

    Everything is in the starter enclosure no need to access the motor, much smarter system....Rod
    The system you describe works well - the human replaces the centrifugal switch. But centrifugal switches don't give a lot of trouble, especially in TEFC motors. The advantage of using a centrifugal switch is that the motor is brought up to speed "automatically" without any additional action other than applying power.

    I'd rather just have to turn power on when I want to use my table saw, without having to hold the button. But I suppose you get used to doing whatever you have to, and it becomes second nature.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  5. #20
    OP here again.

    Thanks again to all who have offered tips. They have been extremely helpful. It's been a while, but it looks like I'm not out of the woods just yet.

    I did take the suggestion of cleaning up the shaft the centrifugal switch moves along. It was mentioned that flyweights swing out as the motor speeds up. The only things that appear to swing out on my motor are two rather light pieces of aluminum. I pulled one off as an example.

    PXL_20210605_171538304.PORTRAIT-01_compress2.jpg

    Should a weight be attached to this?

    Currently, the saw starts up (slightly sluggish) about 50% of the time. When it does, I can make a cut without any bogging down. When it doesn't, it usually trips the breaker (20amp). For every time it does start up, the next time it will trip the breaker. Trying to wait different amount of time between attempted starts yielded the same result. If anyone has had a similar issue, I'd love to hear how you handled it.

    Thanks again in advance for the help!
    Attached Images Attached Images

  6. #21
    OP here.....yet again.

    After another hiatus of trying to figure this thing out I decided to start at the beginning. Specifically the start capacitor.

    The old one was well past it's prime and needed to be replaced (those who have followed along will remover the paper label containing the capacitor's specs was unreadable). An internet search turned up someone else with the same model motor who shared the specs of the capacitor they were having success with. So I bought one.

    Flash forward to about a week ago, I thought "Why didn't I just get in touch with Rockwell in the first place? Surely THEY must know the correct replacement!"

    Well, they didn't.

    But they did refer me to Baldor, who manufactured this specific motor for Rockwell. (If I looked even the tiniest but closer I would seen 'Made by Baldor' on the motor plate!) So I reached out to them.

    Baldor was able to provide me with the actual data sheet for my motor (I now know it was manufactured in Dec. of '77!) including the correct specs for the start capacitor. An online order and a few days shipping later, the correct spec'd capacitor was delivered and installed.

    Now this saw starts up quickly (not sluggish like before) and reliably. I just turned the thing on and off for five minutes and it fired up without fail every time! No more walking around the building to flip a tripped breaker six or seven times everytime I needed to cut something. I finally feel like I have a usable machine.

    So I guess it's never a bad idea to get in touch with the manufacturer! Despite many helpful tips found here, they have the data to help out for sure.

  7. #22
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    so please tell us the specs for future reference.
    Bill D

  8. #23
    Quote Originally Posted by Bill Dufour View Post
    so please tell us the specs for future reference.
    Bill D
    Well, this is sort of the whole point. I got specs from a forum thread like this and it ended up being wrong for me, despite it being even the same model motor. If I list the specs here, someone else might end up getting the wrong part for them.

    The point is to check with your motor's manufacturer. They have access to the information about the entire motor to ensure you are using the right part. Hope this make sense.

  9. #24
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    You have made the valid point that if you can contact the manufacturer, and if that manufacturer is able and willing to provide the information, that's best.

    But it would still be helpful if you were to provide the value here, for those who need an idea of the right capacitance. A capacitor is cheap, and knowing something to try today rather than waiting until tomorrow can be valuable.

    If you want to provide context, a shot of the motor nameplate would be a good accompaniment.
    Last edited by Alan Schwabacher; 09-05-2021 at 9:42 AM.

  10. #25
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    Quote Originally Posted by phillip kerrigan View Post
    Now this saw starts up quickly (not sluggish like before) and reliably. I just turned the thing on and off for five minutes and it fired up without fail every time!
    Nice that you found the right part. But I just want to caution that several starts in quick succession could well cause that new capacitor, or worse, the start winding to fail. Both the capacitor & start winding are running a their full load during a start cycle & the number of starts per hour is to be limited to the manufacturer's spec. It's not too bad with a low inertia load like a table saw, but it's generally something to keep in mind.

  11. #26
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    Quote Originally Posted by phillip kerrigan View Post
    Well, this is sort of the whole point. I got specs from a forum thread like this and it ended up being wrong for me, despite it being even the same model motor. If I list the specs here, someone else might end up getting the wrong part for them.

    The point is to check with your motor's manufacturer. They have access to the information about the entire motor to ensure you are using the right part. Hope this make sense.

    You are correct but what about when the maker goes out of business? I hope this forum, and it's information, will still be available in decades. What about a owner of a Walker Turner tablesaw with a similar size motor. I doubt if Fairbanks Morse has any info about those motors. A real number that is factory approved is a better starting point then just an approximation of what many makers might have used in the past.
    Bridgeport invented the vertical metal milling machine and made them for over 90 years. They used a custom long shaft motor. The company is now gone and sold along with factory information.
    Bill D

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