2 ss1 function, Ss1 function – NORD Drivesystems BU0530 User Manual

Page 25

2 Description of function

BU 0530 GB-3712

2.3.2

SS1 Function

A digital input is always required for the implementation of the SS1 function in order to initiate a braking
process performed by the inverter. For this, the digital input used is set to the function "fast stop" [11].

Note: The optional filter on the digital input is only required in environments with heavy interference.

When the safety function is requested, a controlled stopping procedure is first triggered via the digital input (in
this case DIN1). Here it must be ensured that the drive is brought to standstill within the parameterised fast
stop time (P426). After the elapse of a delay time which is controlled by the switching device, the safe shut-
down method is triggered. The delay time must be dimensioned so that the delay is longer than the fast stop
time plus the DC follow-up time (P559). The delay time must be selected so as to be fail-safe.
Here it should be noted that controlled braking can fulfil the requirements for Safety Category 1. Safety
Category 4 as per DIN EN ISO 13849-1 can be achieved with final switch-off by the triggering of a safe shut-
down method "safe pulse block" or "switch-off of the 24V supply". For this, the same conditions as described in
the examples for the STO function apply. If controlled braking fails then the device switches over to STO (after
the set delay).

NOTE

A separate shielded cable must be used for the "safe pulse block" or "switch-off of the 24V
supply". When using a protective switching device with short-circuit monitored OSSD-outputs,
the safety outputs can be combined in a single shielded cable.

NOTE

The requirements of Safety Category 4 / Performance Level e can only be fulfilled with a safer
shut-down method. Safety Category 1 (and PL c) can be achieved for the digital inputs and
therefore for controlled braking.

DIN1

GND

GND SH

24V SH

24V

Reset

24V

Filter

for

OSSD

optional

Frequency inverter

Use of the

"Safe pulse block"

Emergency

stop

button

Supply voltage

Reset circuit

Input circuit
with short-
circuit
detection

Safety output 1

Safety output 2

Shielded cable to eliminate

errors as per

DIN EN ISO 13849-2