Muriel,
1) Your equipment must be designed to operate from the LISN. It must not
resonate, generate extra ripple, etc. The concept is that EUT sees a low
enough source impedance when connected to any real power distribution system
that it operates in a STABLE mode. That means your input filter supplies
enough local energy storage such that the EUT requires only power-line
frequency replenishment from the mains.
2) The military did use feedthrough capacitors and current probes from 1967
- 1993 to stabilize and measure current conducted emissions. Since '93,
they have gone back to LISNs. And a lot of MIL power supply manufacturers
complained that power supplies designed to operate off the feedthrough
capacitors went unstable when drawing power from LISNs. They had to
redesign their input filters.
Merry Christmas to all!
Ken
----------
>From: Muriel Bittencourt de Liz <mur...@grucad.ufsc.br>
>To: Lista de EMC da IEEE <emc-p...@ieee.org>
>Subject: Doubt with conducted emissions measurement
>Date: Fri, Dec 22, 2000, 10:05 AM
>
>
> 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
>
> -------------------------------------------
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> To cancel your subscription, send mail to:
> majord...@ieee.org
> with the single line:
> unsubscribe emc-pstc
>
> For help, send mail to the list administrators:
> Jim Bacher: jim_bac...@mail.monarch.com
> Michael Garretson: pstc_ad...@garretson.org
>
> For policy questions, send mail to:
> Richard Nute: ri...@ieee.org
>
>
-------------------------------------------
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.
To cancel your subscription, send mail to:
majord...@ieee.org
with the single line:
unsubscribe emc-pstc
For help, send mail to the list administrators:
Jim Bacher: jim_bac...@mail.monarch.com
Michael Garretson: pstc_ad...@garretson.org
For policy questions, send mail to:
Richard Nute: ri...@ieee.org
