I'd have to underscore Keith's responses with just a few of my own - > Q: Finding the EM in a circuit using network analysis:
About 2 years ago I looked into software for EMC work. I was interested in loading in artwork of a pcb (gerber files, Orcad, whatever) for analysis - not system level modeling. I soon found out there were basically three categories of software: 1) Expensive mainframe level software at a university. You contract out their services. 2) Not so expensive $5K to $12K pc loadable stuff. 3) Inexpensive less than $5K pc loadable stuff. I was concentrating on #2 and #3. I uncovered that the software in its attempt to streamline the number chrunching for a pc makes some assumptions with which I didn't agree. For instance, some of the software makes the assumption that ANY ground is a perfect ground. NOT ALL software makes this assumption, so you have to be very careful as to YOUR specific application. Please do not take my word for it. Best to dicuss this with several of the vendors who would be more than willing to out there to provide much help with your needs. > Q: Why does EM happen in motors and drives? Usually it has to do with high current and usually has to do with unintended consequences of that current not going where you think it should nor doing what you think it should. Remember that "EMC" doesn't cover just emissions. If you're drawing alot of current across a board one one ground plane with a mixed layout of digital and analog circuits, then ground bounce, crosstalk, etc ... will freely rain upon your parade.
