Siemens SINAMICS S120 Function Manual page 314

Safety Integrated basic functions
9.5 Safe Brake Control (SBC)
Figure 9-1
The Motor Module carries out a check to ensure that the "Safe Brake Control" function is
working properly and ensures that, if the Control Unit fails or is faulty, the brake current is
interrupted and the brake applied.
The brake diagnosis can only reliably detect a malfunction in either of the switches
(TB+, TB-) when the status changes (when the brake is released or applied).
If the Motor Module or Control Unit detects a fault, the brake current is switched off and the
safe status is reached.
Response time with the "Safe Brake Control" function
The following values can be specified for the response times when the function is
selected/deselected via input terminals:
● Typical response time
● Max. response time in the event of a fault
Examples:
Assumption:
Safety monitoring clock cycle time CU (r9780) = 4 ms and
inputs/outputs sampling time (r0799) = 4 ms
t
R_typ
t
R_max
314
Two-channel brake control, booksize
4 x Safety monitoring cycle CU (r9780) + inputs/outputs sampling time (p0799)
8 x Safety monitoring cycle CU (r9780) + inputs/outputs sampling time (p0799)
= 4 x r9780 (4 ms) + r0799 (4 ms) = 20 ms
= 8 x r9780 (4 ms) + r0799 (4 ms) = 36 ms
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
Drive Functions