EMC-PARTNER EXTTRA3000 E, User Manual

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TRANSIENT3000
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5.5 Hints for the test set up according to IEC standards
We list below those experiences of EMC PARTNER which are important for the success of the various
tests. This information is only partly given in the standards.
Before a test is started, it is important to define which ports (inputs, outputs) must be tested. For the most
important transient tests the ports are given as follows in the European generic standard:
E U T
A C / D C
P o w e r P o r ts
E n c lo s u r e
P o r ts
S ig n a l, D a ta ,
I/O L in e s P o r ts
E a rt h P o r t
figure 5.4
5.5.1 Test set up EFT
Ports which must be tested:
AC/DC power supply, signal, data and I/O lines;
Coupling path:
For EFT pulses, the capacitive coupling is the dominant coupling path. The reasons why the capacitance
coupling path play a dominant role are explained in the book „EMV Störfestigkeitsprüfungen“, published by
FranzisVerlag Munich, or in the report „Schmalbandige Störfestigkeitsprüfungen im n-Sekungen Bereich“
by M. Lutz.
An example will show, that the impedance of EFT spikes at a capacitance of 100 pF (e.g. stray capacitance
can be as high as 100 pF) is very low. As an approximation, the rise time of 5 ns can be converted into a
frequency of 100 MHz, and the impedance can be calculated as:
Z=1/ 2
π
f C = 1/ 6,28 x 100 10
6
x 100 10
-9
= 15 m
Ω
Test set-up:
As shown in the mathematical example, stray capacitance between coupling plate, tester, cables,
laboratory wall and reference ground plates can have a large influence on the test results. Here are some
hints for the set up of an EFT test:
•
The tester must remain on the reference ground plane, and be connected to the reference ground plane
by a low inductive connection.
•
On table-top equipment tests, it is not clear from the existing IEC basic documents 61000-4-4 that the
reference ground plane must be on the table, and not on the floor under the table. The EUT must be
lifted 10 cm from the reference ground
•
All cables must be placed in a reproducible manner. (We recommend a photo of the test set-up)
Safety:
The burst impulses described in the IEC standard 61000-4-4 are not dangerous to persons, because the
energy and the pulse duration are too low. Testers are available on the market with higher spike
frequencies and longer test duration, where the energy is much higher, and therefore more dangerous to
persons.
As mentioned in Chapter 2, EFT disturbances can affect heart pacemakers or hearing aids.