Hi Dave: I had the same question some time back, and came up with the following process.
1) For the resistive component, I applied a resistive load to the AC line, and calculated R = dV/dI 2) For the inductive component, I measured the transient current through an 'X' capacitor at the moment it was touched across the AC line. This requires a storage scope, and a current sense resistor or current probe. Amplitude accuracy is not important, since you're concerned with the period of the ringing. There is a big spike of current, followed by several cycles of ringing. I calculated the line inductance from the ringing frequency. For those who want more precision: - If you know the resonant frequency of the 'X' capacitor assembly, you can calculate the stray inductance, and adjust the line inductance accordingly. - Once you calculate the line inductance, you can correct the steady state impedance in step 1. ---- Patrick Lawler [email protected] On Thu, 19 Sep 2002 08:06:18 -0400, "Spencer, David H" <[email protected]> wrote: >I'm trying to characterize the 50Hz AC line impedance of my facility, for >comparison to the values specified in IEC61000-3-3. I've come across >"generic" short circuit values for the Resistive and Inductive components. >However, I need to determine exactly what these values are ideally through a >combination of measurement and calculation. > >So far, I've taken a large resistive load and measured the voltage drop on >the AC line. From that I calculated the total impedance of the AC line. >However, as you may suspect, with a resistive load, the power factor is 1.0. >So I can't vectorly, calculate the resistive and inductive components. > >Is anyone familiar with a method to measure and calculate those values. The >generic values I have for short circuit condition (which include 4 wires in >a magnetic conduit) come out higher than my measured values, and those do >not include the motor generator source. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
