How Does The Sto Function Work; Activation Status - Delta ASDA-B3 Series User Manual

ASDA-B3

3.9.4 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
Signal
STO
Servo drive output status
Feedback monitoring
(EDM status)
Alarm
Note:
ON = 24 V; OFF = 0 V.
1.
Open = open circuit; Close = closed circuit.
2.
The status of the feedback monitor signal 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 13
4.
Troubleshooting for more details of the alarms.

3.9.4.1 Activation status

STO response time:
When either SF1 or SF2 signal (safety signal source) is low, the circuit cuts off the motor current
within 20 ms.
SF1+
ON
SF1-
SF2+
ON
SF2-
Ready
Open
N/A
H
SF1 / SF2
Motor current
ON
Status of opto-isolator
ON OFF
OFF ON
Torque off Torque off
(SF2 lost) (SF1 lost)
Open Open
AL502 AL501
L
Max. 20 ms
OFF
Wiring
OFF
OFF
Torque off
(STO activated)
Close
AL500
3-99
3