Specifications Of Sto; How Does The Sto Function Work - Delta ASDA-A3 Series User Manual

Wiring

3.10.4 Specifications of STO

The ASDA-A3 series servo drive conforms to the following safety specifications:
3
Item
SFF
HFT
(Type A
subsystem)
SIL
PFH
PFD
Category
MTTF

3.10.5 How does the STO function work?

The STO function controls the motor current by two individual circuits. The two circuits cut off
the power supply to the motor when needed, making the motor free from torque force. When an
STO alarm occurs, determine which alarm is triggered according to the EDM (External Device
Monitoring) status. The following table details how this function works.
Description of STO ON/OFF and EDM status
STO
Servo drive output status
Feedback monitoring
(EDM status)
Note:
ON = 24V; OFF = 0V.
1.
Open = open circuit; Close = closed circuit.
2.
The status of the feedback monitoring signals changes at once according to the status of the safety
3.
signals (SF1 and SF2 signals).
Contact the distributor if AL503 (STO self-diagnostic error) occurs. Refer to Chapter 14 Troubleshooting
4.
for more details of the alarms.
3-116
Safe failure fraction
Hardware fault tolerance
Safety integrity level
Probability of dangerous failure per
-1
hour [h ]
Average probability of failure on
avg
demand
Category
PL Performance level
Mean time to dangerous failure
d
DC Diagnostic coverage
Signal
SF1+
SF1-
SF2+
SF2-
Ready
Open
Alarm
Definition
Status of opto-isolator
ON ON
ON OFF
Torque off
(SF2 lost)
Open
N/A AL502
Standard Performance
Channel 1: 80.08%
IEC 61508
Channel 2: 68.91%
IEC 61508 1
IEC 61508 SIL2
IEC 62061 SILCL2
-10
IEC 61508 9.56×10
-6
IEC 61508 4.18×10
ISO 13849-1 Category 3
ISO 13849-1 d
ISO 13849-1 High
ISO 13849-1 Low
OFF
ON
Torque off Torque off
(SF1 lost) (STO activated)
Open
AL501
ASDA-A3
OFF
OFF
Close
AL500