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Thread: re-wiring a do-all bandsaw

  1. #1
    tesla is offline Plastic
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    Default re-wiring a do-all bandsaw

    Hello folks, this will be my first time writing in. I have acquired a 1981 doall band saw. The head transformer on the unit has a wiring diagram showing 480 to 240 3phase. My intent is to convert the unit from its current 480 wiring structure to 240
    volts. Just to give you some info on the saw, it is mostly original as far as I can see. The motor is a 3 horse power dc motor. It also has a smaller unit for lubrication. My issue is that I have rewired the unit to the best of my knowledge for 240
    3phase and the unit does start, however it does not run in full capacity, approximately 30 seconds goes by and seems to bog down, at this point I shut the unit down with fear of damaging the dc circuit board. If anyone here is familiar with this saw or
    with rewiring such a unit, please shed some light on the situation for me. I will take and provide pictures of the unit Thank you very much, Tesla11.jpg1.jpg2.jpg3.jpg6.jpg

  2. #2
    Shawn Ghormley is offline Stainless
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    Default

    Do you have true three phase power or are you using a rotary converter?
    tesla likes this.

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    Those transformers I saw pictured are single phase transformers.

    Most likely (and I don't know which order)

    - blade welder has a transformer
    - there is a control transformer (for relays, the pilot lights in the on-off buttons, and the actual worklight)

    More than likely the DC drive is operating on the input voltage without modification. I think you will need to come up with a real, 3 phase transformer to have success with this machine.

    I use a similar machine at work although older. Of course its wired for 480vac...and so I don't know anything about converting it to 240vac. Typically/generally, an AC machine is easily convertible due to just changing the termination of 9 wires on a dual voltage motor and perhaps transformer taps on a control transformer. on a DC machine you have to power the DC drive....

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    tesla is offline Plastic
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    I am using a rotary phase converter that I recently built and the phases are within approx. 10% of each other.

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    tesla is offline Plastic
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    Hey Mike if you zoom in on the transformer pictures you will see that they are multi phase 120/240 - 240/480. I have tried to run some simple diagnostic tests but do not know why the machine bogs down after approx 30 secs.

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    bsg-machine is offline Stainless
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    I'm pretty sure the motor drive is single phase on these saws, the welder as well.
    The only three phase will be for a hydraulic motor for the power feed table which your saw does not have.
    I would double check your voltages and look at Doalls website for a electrical schematic.
    Good luck.
    Kevin.

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    tesla is offline Plastic
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    The main electrical plate which is depicted in the picture states that the saw should be wired to 480V 3 phase. The transformers on the unit are multi phase transformers, for a clear view zoom in, they are labelled 120/240 - 240/480. Let me know what you think, thanks.
    Tesla

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    bsg-machine is offline Stainless
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    Quote Originally Posted by tesla View Post
    The main electrical plate which is depicted in the picture states that the saw should be wired to 480V 3 phase. The transformers on the unit are multi phase transformers, for a clear view zoom in, they are labelled 120/240 - 240/480. Let me know what you think, thanks.
    Tesla

    The transformers are multi tap not multi phase.
    The saw needs three phase for the air compressor pump motor, the drive is single phase.
    Look at the connections to the motor drive and you should find only two legs of a three phase input power connected, again the DC drive in these saws are single phase.
    I have a couple of these saws and the drives can be problematic, motor and drive.
    Kevin.

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    Thank you all for your responses. My terminology for the transformers was incorrect, and the correct description was multi tap. Thanks for this correction. Apparently, the saw should be able to run off of single phase. So now my question is, how do I make the hook up? Furthermore, according to Kevin the only component on the unit that requires 3 phase is the compressor pump which is for the blower nozzle. If this is accurate, my intent is to nullify that pump, because I will be hooking up a vacuum nozzle.

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    tesla is offline Plastic
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    I have rewired the saw. The incoming power supply is 230V 3 phase. The trick was that the transformers needed to be wired in a particular sequence. Furthermore the DC board is very sensitive, the in-feed voltage should be as close as possible to 230V single phase. If anyone has an issue with this saw in the future, I have acquired a DoALL library of maintenance manuals, and an OC2 DC motor control manual, let me know, I would be glad to help. Thanks all, Tesla

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    bsg-machine is offline Stainless
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    Tesla,
    Glad you got it going, don't forget to turn the saw speed to zero before turning it off.
    Did you get the OC2 DC motor control manual from Doalls website?
    I have all of the other manuals for my saw except that one.
    Kevin.

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    tesla is offline Plastic
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    Hey Kevin,
    Thanks for the pointer, I wanted physical copies to keep in the shop, so I dropped by a local DoALL shop and picked up a booklet, but I have found a couple of links that you may have some luck with in obtaining a OC2 manual.; http://www.geomartin.com/pdfs/commer...r_control.pdf; Polyspede If this doesn't help, let me know and I will try to scan the booklet for you. Cheers, Tesla

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    bsg-machine is offline Stainless
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    Tesla,
    Thanks for the link to the Polyspede website.
    Kevin.

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    Quote Originally Posted by tesla View Post
    I have rewired the saw. The incoming power supply is 230V 3 phase. The trick was that the transformers needed to be wired in a particular sequence. Furthermore the DC board is very sensitive, the in-feed voltage should be as close as possible to 230V single phase.
    Likely then, if you were using the "generated leg" to power the DC drive that's not the best idea I've had a box full of relays chattering at me by using the generated leg to power a control board, the generated leg sags a lot under motor loads in my experience.

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    tesla is offline Plastic
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    The high leg is powering the light bulb, ect. The two legs that are on the DC board are both metered at 115 - 116V. The DC board voltage needs to be as close as possible to 230 volts. The high leg is within 10% of the other two legs, it reads 120V. This setup is optimal according to DoALL, thanks for your concern.

    Tesla

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