#040 EMI Suppression ~Conducted Emission (Mains Terminal Interference Voltage) V Type Line Impedance Stabilization Network (LISN)~

This time, I will talk about conducted emissions (mains terminal interference voltage).

Mains terminal interference voltage means a conduction noise from an equipment that leaks through its AC cable to such as 100 V, 200 V commercial AC mains and is measured using a V-type line impedance stabilization network (LISN) shown in Figure 1.


Figure 1. V-type line impedance stabilization network (LISN)


If an emission level detected by a measurement equipment exceeds a standard criteria, you need to investigate the noise mode and take countermeasures according to the result.

However, an output of the V-type LISN ( measurement equipment ) has a disadvantage that it is difficult to distinguish whether a observed noise is normal mode or common mode because it detects both normal and common mode current (figure below shows a normal mode current and a common mode current).


(a) Emission measurement for Power line 1


(b) Emission measurement for Power line 2


The solution to this demerit is the Δ (delta)-type LISN.

I’ll tell you more in the next issue.


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