Zuercher, If Gene is right, then there is a really big loop area. Ether the leads to the motor / drive are taking different paths or the is a big ground loop some place.
You could try moving the leads around to confirm what Gene is suggesting. If this is the case, check for ground loops. If there aren't any, then you should consider rearranging you wiring. N. Christopher Perry > On Mar 6, 2015, at 3:14 PM, Charles Steinkuehler <char...@steinkuehler.net> > wrote: > >> On 3/6/2015 1:43 PM, Todd Zuercher wrote: >> What sort of screen? and where is it in relation to the VFD? We have >> a router with 2 VFDs mounted on the outside of a wooden cabinet, and >> they wreak havoc on the CRT display inside the cabinet when they >> accelerate/decelerate (about 6 inches away). It is fine while its >> running, just when stopping and starting. I was thinking I should >> make some sort of metal shield to mount between them, but its been >> that way for more than 15 years without any thing more than this >> aesthetic problem so it hasn't been real high on my to do list. > > I know this one: > > You need a Mu-Metal shield. The VFD is throwing enough current around a > big enough loop it's generating magnetic fields (*NOT* EMI!) and > distorting the video display. It happens on speed changes because > you're drawing lots of current. It should also happen if you load the > motor with a deep cut and push it close to it's rated power level. > > Really nice broadcast studio monitors are magnetically shielded to avoid > this, but just about any other CRT monitor won't be. > > http://en.wikipedia.org/wiki/Mu-metal > > And yes, a magnetic field _is_ a form of EMI (Electro Magnetic > Interference), but it's at a _really_ low frequency and thus is > generally not affected by the typical EMI shielding practices that are > mostly concerned with very high frequency effects. You might have good > luck simply turning the VFD to a different orientation (try rotating it > on it's side or back and see if the problem gets any better or worse). > > -- > Charles Steinkuehler > char...@steinkuehler.net > > ------------------------------------------------------------------------------ > Dive into the World of Parallel Programming The Go Parallel Website, sponsored > by Intel and developed in partnership with Slashdot Media, is your hub for all > things parallel software development, from weekly thought leadership blogs to > news, videos, case studies, tutorials and more. Take a look and join the > conversation now. http://goparallel.sourceforge.net/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
