Sto Function (Safe Torque Off); Introduction To Sto; Precautions For Using Sto Function - Delta ASDA-B3 Series User Manual

ASDA-B3

3.9 STO function (Safe torque off)

3.9.1 Introduction to STO

Once the STO function is enabled, the servo drive stops supplying current to the motor, cutting
off the power supply and torque force. Do not repeatedly use this function for it cannot control
the time the motor stops and the motor speed with parameters. (The STO function is not a stop
function.)
Note: the STO function is supported by B3A series only.

3.9.2 Precautions for using STO function

After the STO function is activated, the servo drive can no longer control the motor. Hence, take
all the potential danger resulted from activating the STO function into consideration. Delta is not
liable for mechanical damage and personnel injury if you fail to observe the following
instructions:
1. For a safety circuit design, make sure the selected components conform to the safety
specifications.
2. Before installation and wiring, read the operation manuals of all the peripheral devices
carefully.
3. Do not touch the servo drive after activating the STO function. The STO function stops the
servo drive from supplying power to the motor but the power supply is not removed from the
servo drive. Thus, there is a potential risk of electric shock.
4. When maintaining the servo drive, use the molded-case circuit breaker (MCCB) or magnetic
contactor (MC) to cut off the power.
5. When the STO function is activated, the servo drive can no longer control, stop, or
decelerate the motor.
6. After the STO function is activated, the servo drive can no longer control the motor, but the
motor can still be moved by other external forces.
7. The EDM signals are not safety output signals. The EDM signals are only for inspecting the
STO function status.
8. The STO function must be powered by the safety extra-low voltage (SELV) power source
with reinforced insulation.
9. Supply power to the STO signals with a single power source, or the leakage current will
result in STO misoperation.
Wiring
3
3-97