EMC EFT and RE Test

Thread Starter

uppi_777

Joined Feb 26, 2018
66
Hello,

Why short cables act as worst case for Electrical Fast Transients Test/Burst and why long cables act as worst case for Radiated Emissions and Radiated Immunity tests?
 

tonyStewart

Joined May 8, 2012
127
Cables have an incremental 0.5 to 1 uH/m inductance.

1. EFT is a conducted ingress test so a short cable presents a lower impedance and higher bandwidth sensitivity to conducted impulse noise.
2. For radiated noise, long cables have mutual coupling that increases with length and thus the "antenna effect" for ingress and egress. This is reduced when CM chokes or "Pi" Line Filters are used.
 
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