On Thu, 25 Mar 2010 10:03:42 -0800, Edward Cole wrote: >For some test equipment, isolation transformers should be used >because they ground circuits that you may not want grounded.
Aside from the fractured logic in this sentence, power isolation transformers, installed per NEC, do NOT isolate the green wire on one side from the green wire on the other, because code requires that ALL grounds (including all green wires, and the chassis of all equipment) be bonded together! NEC also requires that the neutral of every transformer secondary must be bonded to ground, and as noted above, all grounds must be bonded together. So the question is, what, exactly, from a grounding perspective, do you expect to gain by using an isolation transformer? What the isolation transformer CAN do, IF it has one or more Faraday shields, and IF they are properly terminated, is reduce the transfer of noise between line and neutral from one winding to the other. Without those Faraday shields, the capacitance between windings will still couple most of the noise. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
