Presumably these are at 50 Hz only? > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Ralph McDiarmid > Sent: Thursday, July 21, 2005 10:32 AM > To: [email protected] > Subject: RE: AC system impedance > > > I have a number from an old, partial copy of "Rationale for > Emission Limits" from SC77A/WG01. > > Standardized Reference impedance: > Single phase 0.4+j0.25 > 3-phase line 0.24+j0.15 > 3-phase neutral 0.16+j0.10 > > Apparently the investigations made at the time across Europe > concluded about 95% of the line impedances measured would not > exceed those values. > > Ralph McDiarmid, AScT > Compliance Engineering Group > Xantrex Technology Inc. > > -- > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Robert A. Macy > Sent: July 21, 2005 7:22 AM > To: John Woodgate > Cc: [email protected] > Subject: Re: It's too quiet > > John, > > I'm still digesting the thread regarding variability of that test. > > Here, I've measured effective impedance of the lines anywhere > from 0.003 to 0.3 ohms. Once made a big difference in ground > leakage test a for hospital product. > > The US govt paid for a study finding the "expected" > impedance of AC mains over the spectrum of fundamental up to > 1 MHz for residential, simple industrial, and medium sized > industrial. Although very thick, copy makes interesting reading. > > There should be some way to predict the maximum "envelope" > of the harmonics given a perturbation to the impedance. > Or, simply, sweep the impedance over an expected range. > > Variability always suggests lack of controls. After all, > science is in the business of verifiable/repeatable > experimentation. Forgot, EMC is not a science. :-) > > - Robert - >
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