But Jim, The secondary of an isolation transformer is fully isolated - i.e. floating AC. The fact that the neutral of the transformer input side is bonded to the green wire ground is quite a different thing. A proper isolation transformer has no relationship to neutral on the secondary side - only the safety ground and the voltage across the secondary winding.
Remember the old AC/DC receivers that had one side of the AC line tied to the chassis! Every proper service bench had an isolation transformer during that era. 73, Don W3FPR Jim Brown wrote: > On Sat, 27 Mar 2010 09:32:12 -0400, Don Wilhelm wrote: > > >> An isolation transformer *does* isolate the neutral (and the hot), >> > > NO! This is a summary of NEC (National Electric Code) requirements: The > NEUTRAL of a transformer on the secondary side MUST be bonded to the > equipment ground (steel conduit, the green wire, building structure, etc), > and that green wire must be carried from the breaker panel to each outlet and > to the transformer. The neutral conductor that feeds the primary side of the > transformer must be bonded to ground at the service for the building (that > is, the main breaker panel). And, as we all know, all groundes must be bonded > together. Thus, an isolation transformer does NOT isolate either the neutral > or the equipment ground. > > What an isolation transformer DOES do is reduce the voltage between neutral > and ground to zero. It also shortens the return path for leakage currents on > the green wire -- they now return to that transformer, not to the more > distant breaker panel at the service entrance. This has the potential to > reduce noise current on the shield of signal cables. BUT -- the simple > bonding regimen outlined in my Ham Interfacing Power Point is a MUCH less > expensive AND more effective solution. > > 73, > > Jim Brown K9YC > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
