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    #16
    Originally posted by Besoeker3 View Post
    Did you ask for UK or England?
    Often confused by furriners.
    And Brits too.
    We have similar with some people that think Texas is the entire USA
    I live for today, I'm just a day behind.

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      #17
      Originally posted by Besoeker3 View Post
      Did you ask for UK or England?
      Often confused by furriners.
      I asked "highest elevation in UK", but (lacking research skills to check work) took first hit, https://en.wikipedia.org/wiki/Scafell_Pike without digging further. It says England.

      The next hit was https://en.wikipedia.org/wiki/List_o...United_Kingdom which gives Ben Nevis at 1344 metres (4409 ft.).

      I'm just one of those dum sutherners from the Carolinas with the poorest school systems (and a wife who has a masters in information science who would flog me for my accepting Google and wikipedia alone ...)

      Sweep me under the rug and let's get back to electrical issues ...

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        #18
        Like your sense of humour - and, yes that's how we spell it........

        A bigger challenge than altitude for us was ambient. Many of the switch rooms had aircon. But not the tin mining dredgers up the jungle in Malaysia.
        But you know that going in and design the kit accordingly.

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          #19
          Originally posted by Jraef View Post
          Most if not all VFD mfrs provide an altitude de-rating formula for their drives, usually buried in the technical information somewhere. For A-B drives for example they tell you to de-rate the output current by 10% for every 3,300ft (1,000m) above the 3,300ft baseline, or looked at another way, 1% for each 330ft above 3,300ft.

          So for 10,000ft elevation, that's 6,700ft over the baseline, / 330ft = 20% de-rate.
          I agree with Jraef, although in my experience finding this information is not as easy as he suggests. In my experience, a lot of manufacturers publish at altitude spec with no numbers for de-rating. The cooler ambient air temperatures help to some extent.

          In my opinion, 20% de-rate for 3000m (10000 ft) is a good conservative number. I've been working for thirty years at sites from 3000 to 4000 meters (10000 to 13000 feet). I've haven't seen things given a proper de-rating have problems, but a plenty of issues when altitude has been overlooked. I've also seen equipment where no de-rating was applied and it worked fine because it was light, intermittent duty. But remember equipment installed at altitude tends to be on remote sites so it's generally a good idea to make sure it's more than sufficient than risk frequent breakdowns at a remote site.

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            #20
            Originally posted by Timbert View Post
            ... In my opinion, 20% de-rate for 3000m (10000 ft) is a good conservative number. ...
            It's certainly better than not derating at all, but I wouldn't say it's "conservative", just adequate. At 3000 m altitude, there are 26% fewer air molecules in a given volume of air than at sea level.

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              #21
              Originally posted by drcampbell View Post
              It's certainly better than not derating at all, but I wouldn't say it's "conservative", just adequate. At 3000 m altitude, there are 26% fewer air molecules in a given volume of air than at sea level.
              While it's true that the air is thinner (less dense) than compared to sea level. Most electronics are designed to operate to at least 1000 m without de-rating, therefore you only need to consider the difference from the reference altitude to your actual altitude. So, a piece of equipment with 1000 m service ceiling is only 2000 m above that.

              It looks like you used density for you calculation to get 26% difference form 0 to 3000 m, but at 1000 m the difference in density is already over 9%. So, the difference from the normal operating condition (1000 m or less) is only 17%.

              Also, not all heat is lost as a result of convection, some is lost through radiation and conduction. As I mentioned before lower ambient temperatures (typically 2C for each 1000 m) can also be used to your advantage.

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                #22
                Additional considerations

                Originally posted by Timbert View Post
                While it's true that the air is thinner (less dense) than compared to sea level. Most electronics are designed to operate to at least 1000 m without de-rating, therefore you only need to consider the difference from the reference altitude to your actual altitude. So, a piece of equipment with 1000 m service ceiling is only 2000 m above that.

                It looks like you used density for you calculation to get 26% difference form 0 to 3000 m, but at 1000 m the difference in density is already over 9%. So, the difference from the normal operating condition (1000 m or less) is only 17%.

                Also, not all heat is lost as a result of convection, some is lost through radiation and conduction. As I mentioned before lower ambient temperatures (typically 2C for each 1000 m) can also be used to your advantage.
                There are yet other factors that have not existed in the past. The Earth is being exposed to more UV frequencies such as UV " C." This has a very different impact on rapid heating of metals and anything organic for that matter. There is a lot more going on than what is presumed and its not straightforward or necessarily obvious as to what is underlying.
                Microwave Radiation Dangers should be openly discussed

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                  #23
                  Originally posted by GeorgeB View Post
                  I asked "highest elevation in UK", but (lacking research skills to check work) took first hit, https://en.wikipedia.org/wiki/Scafell_Pike without digging further. It says England.

                  The next hit was https://en.wikipedia.org/wiki/List_o...United_Kingdom which gives Ben Nevis at 1344 metres (4409 ft.).

                  I'm just one of those dum sutherners from the Carolinas with the poorest school systems (and a wife who has a masters in information science who would flog me for my accepting Google and wikipedia alone ...)

                  Sweep me under the rug and let's get back to electrical issues ...
                  Thanks for making me laugh.

                  Comment


                    #24
                    Originally posted by StarCat View Post
                    There are yet other factors that have not existed in the past. The Earth is being exposed to more UV frequencies such as UV " C." This has a very different impact on rapid heating of metals and anything organic for that matter. There is a lot more going on than what is presumed and its not straightforward or necessarily obvious as to what is underlying.
                    If your PLC is exposed to sunlight the majority of the time you're not meeting Code. UV at best is a surface effect since by definition it is radiation. In panel heating we would be talking about bulk effects (Boltzmann/Planck aggregate model) so specific wavelengths are meaningless compared to the entire spectrum.


                    Sent from my SM-T350 using Tapatalk

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                      #25
                      Originally posted by GeorgeB View Post
                      With (per Wikipedia) the highest point in UK being 978 metres, not a problem for your local jobs, was it ... ?
                      BTW, UK isn't just England.

                      Oops! I see point has been addressed.
                      It's quite a common matter of confusion, even among Brits.
                      Oh well, VSDs can on 50Hz whichever part of UK in which they are located.
                      Your 60Hz transformers and motors may be less comfortable.
                      Last edited by Besoeker3; 07-04-19, 08:04 AM.

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                        #26
                        Originally posted by Timbert View Post
                        While it's true that the air is thinner (less dense) than compared to sea level. Most electronics are designed to operate to at least 1000 m without de-rating, therefore you only need to consider the difference from the reference altitude to your actual altitude. So, a piece of equipment with 1000 m service ceiling is only 2000 m above that.

                        It looks like you used density for you calculation to get 26% difference form 0 to 3000 m, but at 1000 m the difference in density is already over 9%. So, the difference from the normal operating condition (1000 m or less) is only 17%.

                        Also, not all heat is lost as a result of convection, some is lost through radiation and conduction. As I mentioned before lower ambient temperatures (typically 2C for each 1000 m) can also be used to your advantage.
                        Two different issues. Within a PLC chassis they are kind of like computers. They rely on natural convection to get heat from the components out into the panel air space. They are designed to be packed densely so very little radiation off the front (frontal surface area is small, packed in on the sides). Little you can do about this. That leaves panel cooling itself. There are generally three panel killers. The first is not if but when the MCC environmental controls fail, if it ever had any, which is outside the panel. The second is using NEMA 4X-SS in direct sunlight. The third is using large heat sources like large VFDs, all CVTs of any size, and larger 10 kva+ transformers in the same enclosure without fans. Hoffmann has some excellent design guidelines that keep you out of trouble in terms of panel temperatures. It seems like overkill but it is conservative and works consistently.

                        Sent from my SM-T350 using Tapatalk

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                          #27



                          https://www.slideshare.net/Nawarajin...l-power-system


                          2004_HighAltitude_Hillman-Blattau-Read-Only


                          Electronic components are affected by altitude. Some electronics are more prone than others to suffer failures as a result of low air density.

                          Power supply transformers, chokes and several wire-wound components use the dielectric attribute of air. . . it has its insulating effect.

                          The above link does explain how air affects electronic/electrical components.

                          The second white paper (the bottom one) explains how other solid state component failures are attributed to low air density at high altitude.

                          Note:

                          If the second link from the University of Maryland doesn't work, try copying the URL and typing it in your search engine. It is a copyrighted presentation that may not work in all platforms.

                          I'm still learning how to navigate through my new Linux machine.

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                            #28
                            Originally posted by Besoeker3 View Post
                            Did you ask for UK or England?
                            Often confused by furriners.
                            it's the brexit confusion conurundum. who am us, anyway?
                            ~New signature under construction.~
                            ~~~~Please excuse the mess.~~~~

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