If anyone can help me explain this to my friend in an easier way I would be forever grateful.
This is his problem, but first a little info. He is a very knowledgeable gentleman and has engineered and installed many hydro installations in his life, both from the mechanical and electrical side of the desk. He is a hands on man and can still quote verse and verses on theory (I wish I had his knowledge on math and the sciences)and application. He is in his 90's now and kind of set in his ways, of course I'm not
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Now to his problem. His machine shop is a mess as far as the service is concerned, everybody and his brother has added devices through the years. One day he was having problem with a large milling machine, it would sometimes run for a few minutes and other times the contactor would energize and drop out immediately.
I checked all the common problems usually associated with these older machines and found one of the contactor coil leads grounded to the frame of the machine intentionally and asked him why this would have been done. His explanation was "a 480 volt coil with a ground".The only problem is the building is wired 480 Delta no taps for grounds and no other transformers (for this purpose). I tried to explain the situation but he was adamant that this should work with no circuit returns.
I explained that the coil should be wired with the now grounded conductor tied to one of the other two phases and he explained that it would burn out the coil. Again I explained that the coil was already being supplied by the 480 buss and this would have no affect. I also explained that with the 480 coil grounded to the machine this could be dangerous to an operator if the right (or wrong) problem occurred. Well he wouldn't listen so after he left I wired it correctly and the machine worked as it should.
Now this is one of the old WW2 machines without an LVT for control so the manual push buttons are across the line. I would like to rewire it but he will have none of that. All of the lighting are high bays at 480 with the offices and low voltage through a transformer.
I am at my wits end trying to explain the error in the way this machine was wired. He explains that we just need to "fix the ground problem". Now I am in agreement with fixing the ground problems but I am afraid he has other machines wired the same way and need to get through to him that the grounding system was never designed to be used for this purpose. Anybody have any suggestions for me, oh by the way violence isn't an option
. He's a nice person just a little hard to break old habits. Thanks for any suggestions, Bill
