Siemens SIMATIC S7-400 Reference Manual page 17

Installation Instructions according cULus
WARNING – Explosion Hazard - Do not disconnect while circuit is live unless area is known
to be non-hazardous.
WARNING – Explosion Hazard - Substitution of components may impair suitability for Class
I, Division 2 or Class I, Zone 2
This equipment is suitable for use in Class I, Division 2, Groups A, B, C or D; Class I, Zone
2, Group IIC, or non-hazardous locations only.
CuULu requirements for hazardous location on the battery power supply for CPUs
The backup voltage for a CPU must be supplied over a non-incendive plug connection. The
figure below shows such a plug connection.
(1)
(2)
Figure 1-1
The following conditions apply to the performance characteristics of this connection:
Voc (no load voltage) = 15 V
Isc (short-circuit current)= 50 mA
Ca = Battery/voltage supply capacity
La = Battery/voltage supply inductance
The battery/power supply that powers the non-incendive connection must comply with the
following ratings:
Cc = Cable capacity
Lc = Cable inductance
Note
If you do not know the capacity and inductance of the cable, you can use the following values:
Cc = 197 pF/m (60 pF/ft.), Lc = 0.66 mH/m (0.2 mH/ft)
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
WARNING
1
Battery or supply voltage
CPU with "Ext. Batt." connector
Back-up voltage supply
Battery/Power supply
Voc
Isc
Ca
La
1.1 Standards, certificates and approvals
2
Vmax = 15 V
Imax = 50 mA
Ci = 25 nF maximum
Li = 2 mH maximum
CPU input "Ext. Batt." with cable
≤
≤
≥ Ci + Cc (25 nF + Cc)
≥ Li + Lc (2 mH + Lc)
General specifications
Vmax (15 V)
Imax (50 mA)
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