4
Safety requirements
Requirements for external sensors and actuators
Manual – MOVISAFE
®
CS..A Safety Card
29
– Differential signal pairs (e.g. the track signals A and A, B and B, C and C, Data
+ and Data-) must be routed via twisted cores.
– The encoder cable may exhibit the following maximum capacitances per unit
length:
Capacitance per unit length core / core: CA’ = 70 pF/m
Capacitance per unit length core / shield: CS’ = 120 pF/m
– In the signal path from the encoder to the inverter, the encoder signals must not
branch off to other devices.
4.2.2
HTL encoder cable
•
Use a shielded encoder cable. Connect the shield at both ends.
•
Max. length of the encoder cable: 100 m
•
Use the prefabricated encoder cables from SEW-EURODRIVE. Observe the fol-
lowing requirements if you use other encoder cables:
– The cross section of each core of the encoder cable must be ≥ 0.25 mm
2
. The
resistance load per unit length of the cores must not exceed 78 Ω/km (at
20 °C).
– The encoder cable may not conduct any signals other than the encoder signals,
i.e., the encoder signals must not be conducted with other signals in the same
cable. The encoder signals must be conducted in twisted pairs as follows:
U
B
and GND
A+ and A-
B+ and B-
– The encoder cable may exhibit the following maximum capacitances per unit
length:
Capacitance per unit length core / core: CA’ = 70 pF/m
Capacitance per unit length core / shield: CS’ = 120 pF/m
– In the signal path from the encoder to the inverter, the encoder signals must not
branch off to other devices.
4.3
Requirements for external sensors and actuators
•
The project planner and the user of the system or machine are responsible for the
number and utilization of external sensors and actuators for connection with the
safe inputs and outputs of the MOVISAFE
®
CS..A safety card.
Note that, as a rule, the greater part of the maximum permissible probability of
hazardous errors for the respectively preferred safety classes originates with the
sensors and actuators.
•
Use the calculation tool "SISTEMA" from the "BGIA" (Institute for Occupational
Health and Safety of the German Employer’s Liability Insurance Associations) for
selecting suitable sensor technology and actuators.
•
To meet the required performance level (PL/SIL), you must use suitable and cor-
respondingly qualified sensors and actuators, and observe the relevant wiring dia-
grams and information in the chapters "Safe inputs" and "Safe outputs". The per-
missible encoders are described in the chapter "Encoder requirements".
24842532/EN – 04/2018
