Siemens SIMATIC RF300, Системное руководство

Страница: 119 / 474

3FMBUJWFBJSIVNJEJUZ<>
4ZOUIFUJD "OUJTUBUJD
7PMU
BH
F<
,7
>
①
Relative humidity in offices without humidity control (in winter)
Figure 4-15 Maximum electrostatic voltage to which an operator can be charged, depending on
material and relative humidity
For detailed information on electrostatic discharge, as well as the effects of materials used and
ambient conditions on this effect, refer to the standard IEC 61000-4-2.
4.6.7.2 Discharge and effect
Discharge often comes in the form of a spark that occurs when the electric field strength exceeds
a value of approximately 4 to 30 kV/cm. This can lead to a very rapid increase in the number of
free electrons and ions in the air, causing the air to abruptly become electrically conductive, as
can be seen in lightning during a thunderstorm.
Alternatively, less visible "corona discharge" is possible, in which a discharge occurs between a
strongly curved electrode, comparable to a screw or screw head, and a slightly curved electrode,
such as a flat metal carriers, in which no spark can be seen.
The most spectacular form of an electrostatic discharge, however, is the spark. The possible
consequences are minor discomfort to people, severe damage to electronic equipment, or fires
and explosions if the air contains flammable gases or particles.
However, many electrostatic discharges occur without visible or audible sparks. A person
carrying a relatively small electrical charge may not even feel a discharge, although this
discharge would be sufficient to damage sensitive electronic components. Some equipment can
be damaged by discharges as low as 30 V. These invisible forms of electrostatic discharge can
cause total failure or less noticeable damage, potentially affecting the long-term reliability and
performance of electronic equipment. For some devices, the damage may go unnoticed for
much of their operating life.
Planning the RF300 system
4.6 Guidelines for electromagnetic compatibility (EMC)
SIMATIC RF300
System Manual, 02/2021, C79000-G8976-C345-09
119