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Thread: Running master/slave VFD

  1. #11
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    Quote Originally Posted by Besoeker View Post
    Lead/lag in what sense?
    During one cycle of operation VFD A operates first (Lead) to supply water with VFD B (Lag) starting after a predetermined time or continued pressure drop until pressure is satisfied.

    The next cycle starts with VFD B taking Lead and A taking Lag duty. Purpose being to get similar run times for both. In reality, both pumps are worn out at about the same time.

    Tracking the actual run times of each can tell you how well that particular pump is operating in comparison to the other IF someone is paying attention.
    Tom
    TBLO

  2. #12
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    Quote Originally Posted by ptonsparky View Post
    During one cycle of operation VFD A operates first (Lead) to supply water with VFD B (Lag) starting after a predetermined time or continued pressure drop until pressure is satisfied.

    The next cycle starts with VFD B taking Lead and A taking Lag duty. Purpose being to get similar run times for both. In reality, both pumps are worn out at about the same time.

    Tracking the actual run times of each can tell you how well that particular pump is operating in comparison to the other IF someone is paying attention.
    Thank you kindly for that. It isn't what I would have termed master/slave but I understand the application.

    For me, the master/slave arrangement, commonly used on paper making machines, would be two or more drives mechanically coupled via a "felt" or other material. The master controlled the speed. The slave(s) shared the load torque. Mostly used at the "wet end".
    Si hoc legere scis nimium eruditionis habes.

  3. #13
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    Quote Originally Posted by Besoeker View Post
    Thank you kindly for that. It isn't what I would have termed master/slave but I understand the application.

    For me, the master/slave arrangement, commonly used on paper making machines, would be two or more drives mechanically coupled via a "felt" or other material. The master controlled the speed. The slave(s) shared the load torque. Mostly used at the "wet end".
    I described Lead/Lag as I would use it. Not Master/Slave.

    The only M/S I was involved with was with plastic extrusion into sheets. 1/8" to 5/8" in thickness. I would guess in a similar fashion as to your paper making, although not near as critical.
    Tom
    TBLO

  4. #14
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    The OP used the term "master-slave" but the description of operation he offered appeared to be more along the lines of lead-lag, hence the comments to that effect. It's really incumbent upon the OP to clarify or at least tell us he got what he needed, rather than keep speculating ad nauseam.
    __________________________________________________ ____________________________
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  5. #15
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    Quote Originally Posted by ptonsparky View Post
    I described Lead/Lag as I would use it. Not Master/Slave.

    The only M/S I was involved with was with plastic extrusion into sheets. 1/8" to 5/8" in thickness. I would guess in a similar fashion as to your paper making, although not near as critical.
    I've been around the block a few times, ridden hard, and put up wet. It gave me a wealth of opportunities that probably not many in our field get..
    From the frozen Great Lakes to the Sahara Desert,
    Paper, steel, water, plastics, anodising, petrochem, zinc mill in Turkey, Character building stuff I guess.

    But drives for paper making were the most critical in terms of dynamic performance.
    Although some of our machine tool drives eclipsed that by at least an order of magnitude - 10,000 rpm to zero within less than a second to within half a degree of position accuracy. To the eye it looked instantaneous.
    Si hoc legere scis nimium eruditionis habes.

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