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    #16
    Originally posted by ptonsparky View Post
    If they decide on the drives they will be in an attached building. How do the drives affect the tags or visa versa?
    Not sure why the tags would make a difference, but there is lots of documented evidence of the Common Mode Noise created by VFDs causing cows to quit producing milk because they can feel a sensation in their teats when hooked up to the milking machines. The trick is to be fastidious about all ground connections and shield grounding, use what are called "Common Mode Cores" (ferrite rings) on the output conductors and in some cases to have shielded drive isolation transformers feeding the VFDs. I have a friend in New Zealand that spent a LOT of time and money investigating this because it was causing dairy farmers near him to lose revenue.
    http://www.lmphotonics.com/farm/dairy-shed.php
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

    I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

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      #17
      Originally posted by ptonsparky View Post
      If they decide on the drives they will be in an attached building. How do the drives affect the tags or visa versa?
      I'm told it's affects the devices trying to read the cows ear tags. The VFD and output wiring are basically like a giant FM antenna that cause interference issues. The closer the VFD and shorter the motor leads, the less interference.

      Over here, they read the ear tags on the milking carousels for individual cow statistics, they also use the tags to automatically open and close sort gates to sort cows into certain pens, they are used for body condition cameras, and on and on. In the freestall barns, they have activity sensors to monitor for cows in heat for breeding purposes and the employees also use hand scanning RFID wands for identifying and working with the animals directly.

      As you can tell, they use the RFID tags for tracking almost everything.

      If the farm you're at doesn't use RFID ear tags, or isn't planning on doing this anytime in the future, then it's not a problem.

      https://www.valleyvet.com/ct_detail....6-E73CF9633B99.

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        #18
        [Intercom announcement] "Uh Bessie, the system is saying that you are a quart low today. Everything all right girl?"
        [Bessie] "Mooo..."
        [Intercom] "Well, pick it up or we're making a reservation for you at the McDonalds spa..."
        __________________________________________________ ____________________________
        Many people are shocked when they discover I am not a good electrician...

        I'm in California, ergo I am still stuck on the 2014 NEC... We'll get around to the 2017 code in around 2021.

        Comment


          #19
          Some truth here. Common mode issues are caused by failing to run a separate EGC directly between the VFD and the motor frames. This is not optional and bonding through conduit is not good enough. Nothing to do with ferries that are really just cheap reactors.

          Second is that beyond about 10-100 feet and this distance is drive specific you will have issues with reflected waves. Based on the application I would assume this is an issue. The best solution out there is a sinus filter but a close second is a dc/dt filter. Output reactors reduce output by about 5% and do little to help and the cost is not much different from a dv/dt filter. A DC choke works really good too, comparable to the dv/dt filter at 1/4 the price but not all drive manufacturers have one available. On the line side it depends on how much of the load on the transformer is the VFD. Again a DC choke makes a big difference but alternatively an isolation transformer does a great job and eliminates all odd harmonics.


          Sent from my iPhone using Tapatalk

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            #20
            Originally posted by Cow View Post
            I'm told it's affects the devices trying to read the cows ear tags. The VFD and output wiring are basically like a giant FM antenna that cause interference issues. The closer the VFD and shorter the motor leads, the less interference.
            .........

            https://www.valleyvet.com/ct_detail....6-E73CF9633B99.

            Those readers and tags are on the LF (low frequency) RFID band with carrier and modulation sidebands in the vicinity of 130 to 140KHz. So filtering of the VFD output to get sufficient attenuation at this frequency (including the common mode) may be necessary to reduce interference if such RFID systems are used. Conduit and even twisting wires to reduce magnetic coupling would likely help. And reducing conductor length to the extent possible as mentioned above will also help.

            I'm very familiar with UHF band RFID but not with LF band that uses near field magnetic coupling between coils (instead of far field coupling and resonant tag antennas at UHF).

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              #21
              Originally posted by Cow View Post
              I'm told it's affects the devices trying to read the cows ear tags. The VFD and output wiring are basically like a giant FM antenna that cause interference issues. The closer the VFD and shorter the motor leads, the less interference.

              Over here, they read the ear tags on the milking carousels for individual cow statistics, they also use the tags to automatically open and close sort gates to sort cows into certain pens, they are used for body condition cameras, and on and on. In the freestall barns, they have activity sensors to monitor for cows in heat for breeding purposes and the employees also use hand scanning RFID wands for identifying and working with the animals directly.

              As you can tell, they use the RFID tags for tracking almost everything.

              If the farm you're at doesn't use RFID ear tags, or isn't planning on doing this anytime in the future, then it's not a problem.

              https://www.valleyvet.com/ct_detail....6-E73CF9633B99.
              They were using one of these the last time I was there.

              They don’t track the individual production per cow but do know when that average drops on at least a daily basis.

              They were hoping to save some up front costs and add a VFD per group vs individual fans. I’m thinking 2000 feet of VFD cable alone might negate that thought.

              On to plan B.
              Tom
              TBLO

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                #22
                Click image for larger version

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                The fans fed by these two EMT conduits are running. It may not be easily seen, but the conductors are holding the conduit up.
                Tom
                TBLO

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                  #23
                  Originally posted by ptonsparky View Post
                  They were using one of these the last time I was there.

                  They don’t track the individual production per cow but do know when that average drops on at least a daily basis.

                  They were hoping to save some up front costs and add a VFD per group vs individual fans. I’m thinking 2000 feet of VFD cable alone might negate that thought.

                  On to plan B.
                  VFD cable is useful to roughly double the distance before reflected wave is an issue. For example on Allen Bradley Powerflex drives the maximum line length goes from 50 to 80 feet. That's it. Even then it's a joke. #14 THHN which has the thinnest insulation is rated 600 V but passes a minimum of 2200 V by Codes. Actual testing by NEMA shows it works to 2800+ regardless of brand. XHHW which is thicker goes to 3200 V. VFD cable goes beyond these ratings but let's get back to the motor. Very old motors without phase papers are limited to 1000 V. Inverter duty motors with phase paper built to beyond Code specs hit 1700-1800 V peak ratings. So if THHN is rated to 2200 and tests to over 2800, can a VFD cable manufacturer please explain what VFD cable does other than line their pockets?

                  The issue is protecting the motor. The motor has the tighter limits. Protect the motor and the cable doesn't matter. VFD cable is a ripoff.

                  AB sells VFD cable so they push it but most dealers do not bother to read their own manuals. At 2000 feet it's useless. So are dv/dt filters. Only a sinus filter will handle that distance. With that filter, VFD cable does nothing but help improve the profit margin.

                  A ship loading facility I visited at a port used all AB equipment. We rebuilt the gear box but i was sent out because we had fluting in the gear box (???) Its not even a close coupled motor like a C face buf its an all metal coupling. As per the AB distributor they spent obscene amounts of money pulling out THHN and installing VFD cable for their 500-1000 foot runs. Motors still failed in 6 months. The gear box failed in 18 months. Transients were not just random but 2 KHz (drive carrier frequency). Ringing transients were stupidly high, over 2 kV, on the phase conductors. Well at least they won't have to rerun cable! We could have dropped TCI filters in their huge drive cabinets for less than the cost of the cable itself.

                  Sent from my SM-T350 using Tapatalk

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                    #24
                    Originally posted by ptonsparky View Post
                    [ATTACH=CONFIG]23345[/ATTACH]

                    The fans fed by these two EMT conduits are running. It may not be easily seen, but the conductors are holding the conduit up.
                    Nice so cable needs rerun anyways. In that environment wouldn't MC make more sense?


                    Sent from my SM-T350 using Tapatalk

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                      #25
                      Originally posted by paulengr View Post
                      Nice so cable needs rerun anyways. In that environment wouldn't MC make more sense?


                      Sent from my SM-T350 using Tapatalk
                      Nothing metallic makes sense in there. It will all be sch 40.
                      Tom
                      TBLO

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