Measures For Suppressing Interference From Fluorescent Tubes In Cabinets - Siemens SIMATIC S5 Manual

Routing cables; connecting and installing bus connectors
Circuit with
varistor
Circuit with RC
element
Programming
units: connection
to power supply
Cabinet lighting
5-14
A circuit incorporating a varistor has the following properties:
The amplitude of the shutdown overvoltage is limited, but the overvoltage
is not suppressed
Overvoltage slope is uniform
Shutdown delay is slight
A circuit incorporating an RC element has the following properties:
The amplitude and slope of the shutdown overvoltage are reduced
Shutdown delay is slight
Each cabinet must feature a power point for connecting the programming
units to the mains supply. These power points must receive their supply via
the distribution board to which the protective conductor of the cabinet is
connected.
Use bulbs such as LINESTRA
fluorescent tubes, because they generate interference fields. If there is no
alternative to fluorescent tubes, adopt the measures illustrated in Fig. 5-4.
Screen grid over tube
Figure 5-4

Measures for suppressing interference from fluorescent tubes in cabinets

bulbs for the cabinet lighting. Do not use
Shielded cable
Metal-encapsulated switch
Mains filter or shielded supply
cable
ET 200 Distributed I/O System
EWA 4NEB 780 6000-02a