DC link components 
7.2 Braking Module Booksize 
SINAMICS S120 Combi 
Manual, (GH9), 07/2016, 6SL3097-4AV00-0BP5 
181 
 
X21 digital inputs/outputs 
Table 7- 9  X21 digital inputs/outputs 
1  DI low: enable Braking Module 
DI high: Inhibit/acknowledge 
Edge change, high → low: fault acknowledgement 
Voltage: -3 … +30 V 
Current consumption typical: 
10 mA at 24 V DC 
Level (incl. ripple) 
High level: 15 … 30 V 
Low-level: -3 … +5 V 
2  DI low: braking resistor not activated manually 
DI high: Braking resistor controlled manually 
2)
If X21.1 and X21.2 are activated simultaneously, 
the Braking Module inhibit has priority. 
3  DO high: no prewarning 
DO low: Prewarning, disconnection imminent 
Max. load current per output: 100 mA 
Continuously short-circuit proof 
Voltage: 24 V DC 
4  DO high: ready for operation, no fault 
Ground 
Type: Screw terminal 1 (Page 307) 
Max. connectable cross-section 1.5 mm
2
 
Tightening torque: 0.22 … 0.25 Nm 
DI: digital input; DO: digital output; M: Electronics ground
The fast discharge function is used for discharging the capacitors in the DC link after interruption of the line supply and
may be used a maximum of 1 to 2 times per week.
Terminal X21.1 - inhibit/acknowledge 
Applying a high signal to terminal X21.1 inhibits the Braking Module. On a falling edge, 
pending error signals are acknowledged. 
Terminal X21.3 - prewarning 
When a prewarning is sent, disconnection of the braking module is imminent. 
This may be due to the following causes: 
● The temperature of the Braking Module is 80 % of the maximum value.
● 80 % of the maximum on-load factor of the braking resistor has been reached (I
2
t
monitoring).
● 80 % of the maximum braking energy of the braking resistor has been reached.
● An incorrect braking resistor is connected (only braking resistors approved by Siemens
for this component are identified automatically).
In the event of an overtemperature, the error cannot be acknowledged until after a cooling 
phase.