The standard considers the effect of both current and voltage distortion on the UUT that is connected to the DC test bus. There is a table of frequencies that will individually modulate the bus.
At first glance, the test conditions do not make much sense, but I have spent enough time on AAVs, M1 tanks, and various aircraft to have a general appreciation of the rationale. There are other tests in this std that are analogous to 61000-4-11. luck, Brian > -----Original Message----- > From: [email protected] [mailto:[email protected]]On Behalf > Of Ken Javor > Sent: Wednesday, April 25, 2007 9:00 AM > To: 'IEEE EMC Discussion Group' > Subject: Re: MIL HBK 704-8 distortion factor > > Correction: My response went to the definition of voltage > distortion on a dc > bus. I am not familiar with any particular test method for > measuring the > distortion due to a load. I would think that if you are controlling > distortion from a particular you would have to measure > current distortion > from a stiff source, not the voltage distortion I described. > And I also > think you would have to be very careful to discriminate between audio > frequency effects and the distortion due to a dc/dc converter > - the latter > should not be considered a voltage distortion controlled by > MIL-STD-704, it > is an rf effect. That's why in my original response I said > that a voltage > distortion spec and measurement should be low-pass limited. > > > From: "Brian O'Connell" <[email protected]> > > Date: Wed, 25 Apr 2007 08:27:30 -0700 > > To: "'IEEE EMC Discussion Group'" <[email protected]> > > Subject: RE: MIL HBK 704-8 distortion factor > > > > "Distortion" for a 28Vdc bus, in accordance with MH-704-8, > is defined in > > that standard and in MH-704-1 (for performance level). The > diagrams in > > MH-704-8 clearly indicate test requirements/conditions. Do not use > > additional equipment or deviate from these requirements. > This is a simple > > test (but long), so do not make it complicated. Performance > requirements > > are dependendent on the UUT specs. > > > > The tester should understand that these test conditions are > not contrived, > > and are based on empirical measurements from various > aircraft and ground > > vehicle 28V bus. > > > > In a previous life, I used programmable sources from > Chroma, Xantrex, and > > Elgar for this test. Some of these sources can provide > direct modulation, > > so the transformer-coupled generator would not be required. > > > > luck, > > Brian - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
