Hello Group!
First of all, I wish a merry christmas and a happy new year for the list
members.
Second, I'd like to solve a doubt. It concerns the methodology of
conducted emissions tests.
Let's suppose a power electronic equipment (static converter) that has a
boost converter in the entrance that's used for power factor correction
(PFC). When I make a conducted emissions test, I plug the converter in a
LISN, then I plug the LISN in the outlet, this way (the classical way):
Equipment => LISN => Outlet (Mains)
Well, the LISN consists of a RLC network that has the purposes of:
- prevent that external interference from the mains contaminate the
measurement
- create a stabilized impedance (50 ohms) in the frequency range of
interest (150kHz-30MHz) to make results repeatable, from site to site.
Ok, what I've said until here is well known and is present in every book
about this subject of EMC.
My doubt is this: The LISN can't interfere in the functional operation
of the converter? Things like resonance, extra ripple can't occur? And,
imagining the worst scenario, can the LISN make my equipment not work
according to what's expected?
Another thing I was thinking about is the fact that the military tests
os conducted emissions are done with a probe, and not using a LISN.
I'm very curious about this subject because I was asked about this
question and I became very surprised, because I have never thought about
this. We are, generally, so interested in results that we forget to ask
the "basic questions" sometimes.
Well, I think that's all. Thanks in advance for those who can help me.
Best Regards
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Eng. Muriel Bittencourt de Liz
EMC Testing and Troubleshooting
Group of Conception and Analysis of Electromagnetic Devices
Federal University at Santa Catarina
Florianópolis, SC, Brazil
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