We have a radio comms site with multiple equipment. Originally the site was set up with a positive ground at the rectifiers. We have some new equipment that is powered from the rectifier shelf, that will not work well with a positive ground. We were thinking of changing one of the rectifiers to a negative ground. My question is would this cause a problem?
In my mind, having a positive ground and negative ground connected to the same main site ground just seems wrong, but is it? Would there really be a conflict here or not?
All voltage is DC, with exception of input power to rectifier shelves (120AC).
Best Answer
If you are using bridge rectifiers then you'll have a big problem with a set of rectifiers for positive ground and a set of rectifiers for negative ground: -
Shown in red is the almost-short-circuit current that will flow for positive half-cycles of the AC waveform (shown as a circle). It's the same for negative half-cycles too but through different diodes.
What springs to my mind is the use of a DC-to-DC convertor that isolates out a DC supply that is equal to your current DC supply voltage. Because it is an isolated voltage (internal switching power supply and transformer) either of its two leads can be conected to ground.