Sto Function (Safe Torque Off); Introduction To Sto; The Potential Danger Of Sto - 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 does not stop
the motor with active force.
Note:
1. The STO function is supported by the B3A series only.
2. STO certification application is in progress.

3.9.2 The potential danger of STO

After the STO function is enabled, the motor is no longer controlled by the servo motor.
Thus, take all the potential danger resulted from enabling 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, read the safety instructions in the STO-related user manual for the
components you use.
3. Do not touch the servo drive when the STO function is enabled. Although the power to the
motor is cut off, there is residual electricity since the power supply is not completely
removed from the servo drive. When maintaining the servo drive, use the molded case
circuit breaker (MCCB) or magnetic contactor (MC) to cut off the power.
4. When the STO function is enabled, the servo drive can no longer control, stop, or
decelerate the motor.
5. After the STO function is enabled, the servo drive no longer controls the motor, but the
motor can still be moved by other external forces.
6. The feedback monitoring output signal (FDBK) is only for inspecting the STO function status
rather than for safety output.
7. The STO function must be powered by the safety extra-low voltage (SELV) power source
with reinforced insulation.
8. Power the STO signals with single power supply, or the leakage current will result in STO
malfunction.
Wiring
3
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