NORD Drivesystems BU0530 - Manual (Page 23)

2 Description of function
BU 0530 GB-3712 23
2.3 Examples / Implementation
The following illustrates several examples of solutions for the safety functions STO and SS1.
2.3.1 STO function
Normally, a protective switching device is used to implement a safety function. The safety category of the
function is determined by the component with the lowest category.
In this example, Safety Category 4 as per DIN ISO 13849-1 can be achieved. The prerequisite for this is that
the emergency stop button, the protective switching device and the wiring fulfil the requirements for Category
4. For example, this can be achieved as follows:

Redundant protective switching device with self-monitoring

Dual-channel input circuit with short-circuit recognition (and appropriate emergency stop button)

Safety output with periodic switch-off tests (OSSD)

Elimination of errors as per DIN ISO 13849-2 for the wiring between the switching device and the input
terminals of the safe shut-down method used, by the use of a shielded cable and connection of the
shield at both ends.
NOTE
If the "Safe pulse block" triggers for an enabled frequency inverter, error E018 (18.0 safety
circuit) is triggered.
The typical reaction time can be reduced by the additional use of a digital input (e.g.: DIN1), which must be
parameterised for the function "Block voltage":
Note: The optional filter on the digital input is only required in environments with heavy interference.
A second safety output is required to control the digital input.
DIN1
GND
GND SH
24V SH
21
40
88
89
24V
24V
24V
Frequency inverter
Use of the
"Safe pulse block"
Reset
Emergency stop button
Reset circuit
Safety output 1
Safety output 2
Supply voltage
Input circuit
with short-
circuit detection
Shielded cable to
eliminate errors as per
DIN EN ISO 13849-2
Filter
for
OSSD
optional
GND SH
24V SH
88
89
24V
-
24V
Frequency inverter
Use of the
"Safe pulse block"
Reset
Emergency stop button Reset circuit
Shielded cable to eliminate
errors as per
DIN EN ISO 13849-2
Input circuit
with short-
circuit
detection
Supply
voltage
Safety output