Mr. Lacey's final comment is illustrative of what has been my point of view. Why worry about what a specific source impedance is at the line frequency (50/60/400 Hz)? Rather, measure current (steady-state/harmonics/inrush/whatever) while verifying that resultant bus potential (Volts) is negligibly small. In so doing, you verify the maximum current the EUT will generate under any circumstance. Comments?
---------- >From: "Lacey,Scott" <[email protected]> >To: "'[email protected]'" <[email protected]> >Cc: "'[email protected]'" <[email protected]> >Subject: RE: 60 Hz Power Line Impedance >Date: Mon, Nov 15, 1999, 5:40 AM > > > David, > > The line impedance will vary considerably with location and type of > distribution transformer. The impedance of the secondary will relate to the > primary (power utility) impedance as the square of the turns ratio, plus > line drops. Your best bet would be to start with inquiries to the power > companies and the transformer manufacturers. > > As to the impedance of a specific power line, the usual method of > measurement is to connect a power line qualifier (consisting mainly of a > capacitor of known value) to the output of a device which switches at ninety > degrees phase angle and measure the inrush current. KeyTek sells a line > qualifier for use with their EMC Pro > unit. We bought one for power interruption testing, and are gradually having > options added. They offer options for surge, EFT, etc. > > Equipment should always be designed to work over a wide range of line > impedance. I once measured 300 amps inrush current at the company facility, > and 1200 amps at the power supply vendor's test bench, for the same power > supply! > > Scott Lacey > > -----Original Message----- > From: [email protected] > [SMTP:[email protected]] > Sent: Friday, November 12, 1999 2:32 PM > To: [email protected] > Subject: 60 Hz Power Line Impedance > > > > Fellow Networkers; > > Does there exist information about the impedance (at 60 Hz) of > typical > power line networks here in the US? > > In Europe, I know they use a specified reference impedance (at > 50 Hz) > for flicker testing, which is (0.24 + j0.15) Ohm for line and > (0.16 + > j0.10) Ohms. This represents, I understand, the European > public > network impedance as seen at the point of "common coupling" > (i.e., > connection to the homes service entrance). > > David Tarnowski > Whirlpool Corporation > Global Laundry Controls > St. Joseph, MI > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
