R.T.A. s.r.l. – XPETME05 – 11/20
24/29
12 - STO FUNCTIONS (X-PLUS ET S4 only).
12.1-
SYSTEM CONFIGURATION DESCRIPTION
1
2
3
4
5
6
7
8
A
A -
B
B -
51
52
53
54
55
STO2
-
-
STO1
SAFETY UNIT
Safety
output
Emergency
Stop button
SHIELD
N
21
22
23
24
25
Monitor
-
Feedback
input
Fig. 15 – Connection scheme.
12.2-
STO FUNCTION
Safe-torque-off function reduces injury risks and ensures the safety for those who work near moving
parts of equipment. This function employs 2-channel input signal that independently block the motor
current.
12.3-
STO FUNCTION SCHEME DESCRIPTION
STO function disables the current flowing into motor windings.
Each of two STO1 and STO2 channels act independently to shut down motor current. A failure of
one single channel does not compromise the activation of the safety function.
12.4-
STANDARD CONFORMITY
STO function meets the following safety standards:
•
IEC 61800-5-2, safe torque off (STO)
•
IEC 61508, SIL3
Probability of a dangerous failure per hour, with use of Error Detection Monitor (EDM) to grant
Diagnostic Coverage (DC), is described in the following table:
PHFd
Test Timing
Mission Timing
SIL
3.50x10
-10
1 month
10 years
3
4.00x10
-10
10 years
10 years
3
