SIOV Metal Oxide Varistors - DEMAR

Application and Design Examples
FRAME4/home/SMC-Archiv-DB/GG-KB-engl/DB-SIOV_97_BNR-B462-P6214-X-X-7600/R-Beispiele
Average power dissipation
According to equation 18, applied energy of 0,05 J every 10 s produces an average power dissipation
of
P*
W*
= -------
T*
0,05
= ---------- = 0,005 W
10
The product table shows a maximum dissipation capability of 0,02 W for SIOV-S07K20 and
CU4032K20G2. So on this point too, the choice is correct (equation 11).
For the sake of completeness, the minimum permissible time between two applications of energy
is calculated (equation 19):
W*
T min = ------------
P max
0,05 J
= ------------------ = 2,5 s
0,02 W
For CN1206K20G, with P max = 0,008 W the result is
W*
T min = ------------
P max
0,05 J
= --------------------- = 6,2 s
0,008 W
Maximum protection level
The V/I curve for S07K20 and/or CU4032K20G2 shows a protection level of 60 V at 1 A for the
worst case position in the tolerance field (PSpice supplied by S+M: TOL = +10).
The protection level for CN1206K20G is 55 V.
This means that all three types meet the requirement for a protection level < 65 V.
The hicap varistors SHCV-SR.K20... also satisfy all the selection criteria. Their use can have a positive
effect as far as contact erosion and RFI are concerned. They also mean a reduction of the maximum
protection level to 50 V.
3.2 CE conformity
A wide range of legislation and of harmonized standards have come into force and been published
in the field of EMC in the past few years. In the European Union, the EMC Directive 89/336/EEC of
the Council of the European Communites has come into effect on the 1st of January 1996. As of
this date, all electronic equipment must comply with the protective aims of the EMC Directive. The
conformity with the respective standards must be guaranteed by the manufacturer or importer in
the form of a declaration of conformity. A CE mark of conformity must be applied to all equipment
[1].
As a matter of principle, all electrical or electronic equipment, installations and systems must meet
the protection requirements of the EMC Directive and/or national EMC legislation. A declaration of
conformity by the manufacturer or importer and a CE mark are required for most equipment. Exceptions
to this rule and special rulings are described in detail in the EMC laws.
[1] Kohling, Anton “CE Conformity Marking”
ISBN 3-89578-037-5, Ordering code: A19100-L531-B666
Siemens Matsushita Components 53