2
Description of the safety function STO
Festo – GDCP-CMMS-AS-G2-S1-EN – 1306NH – English
13
2.2.1
Description of the safety function STO
Use the “Safe Torque Off ” function (STO) whenever you have to reliably disconnect the energy supply
to the motor in your application.
The safe torque off function switches off the following
Fig. 2.2.:
–
Driver supply for the power semiconductor.
–
Activation of the power semiconductor (PWM).
Note
The STO function request must always run over X3.2 and X1.21 (end stage enable).
2nd switch-off
path
Activation of driver supply relay
(switch-off of the driver supply)
high = driver supply on
low = “pulse blocker” active
Driver
supply
monitoring
Potential-free driver
supply acknowledg-
ment contact
15 V - IGBT
driver supply
(+15 V_TR)
+15 V_TR_switched
1st switch-off path
Output stage driver
IGBT output stage
DIN4 goes
directly to the
µP and switches
off the PWM
Out
put
st
ag
e
e
n
abl
e
D
IN
4
C
o
nt
ro
lle
r
e
na
b
le
D
IN
5
Fig. 2.2
“Safe Torque Off ” - functional principle for CMMS-AS-...-G2
With the Safe Torque Off function (STO), the energy supply to the motor is reliably interrupted by
switching off the end stage enable and supply to the final output stage. The drive cannot generate
torque or any force and so cannot make any dangerous movements.