On Sun, May 27, 2018 at 12:03 PM, a k <pccncmach...@gmail.com> wrote: > hi > i was thinking about problem that i got and have some ideas. > when one come close to the large motor - any motor - size of motorcycle or > small car , possible to notice that hair - start move. like someone > touching it. > right? > this is magnetic field touching. right? > such large motor always grounded. only super large business use such > motors. > i am talking about such large motor because no need to special > magnetometor to detect magnetic field- hair is enough .
If it is moving hairs it s not a magnetic field. You can verify this by experiment. Get a powerful magnet and place it near the tiny hairs on your forearm and notice the magnet has no effect. What what is moving the hairs? It is the "E-Feild" or electric field. Magnetic and electric field go hand in hand. Te hairs likely if it is a dry da or there is A/C in the shop have a static charge on them so an electric field would produce a force. A magnetic field is very hard to shield, you need material that is "magnetic" like steel and to fully enclose the motor and usually you need a lot of it. Sheet steel can work but cast iron would be better. But an e-feild is easier, any conductive material even as thin as foil, they even make conductive paint for this purpose. All of the shielded cable you have seen, the kind with foil or braid around the conductors is design to shield electric (not magnetic) fields. The motor housing like is a good electric field shield and "gets" most if it. Add one more ground shell and maybe you get more of it. But then any good shield will also trap heat. You compromise the effect of the shield if you make holes in it. Without the holes the motor will overheat. Likely the engineers who designed the motor thought they hit on a good enough compromise between cooling and shielding. One other experiment you might try is wearing a grounded wrist strap, the kind used by people who assemble electronic parts, These have a 1M resister in series to ground. They also use conductive clothing and the environment is treated with condition sprays and on. It is really hard to get rid of static charge but the wrist strap does an 90% job with 10% of the effort. In contrast to ectronic assembler machinists do all the can you put MORE charge into themselves, they stand on rubber mats and operate machines with moving parts. I'd be interested to hear the results of your experiments with magnets and with removing static charge from yourself. -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
