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Rev. 1.0
2016/7/30
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SS03/05/10-EC Hardware Manual
2.10 Connecting the STO
On the SS EtherCAT step-servo drives, the STO (Safe Torque Off) function is connected via port
CN4. The STO function shuts off the motor’s current turning off the motor output torque by forcibly
turning off the signal of the drive’s power transistor. This is done internally through the STO Input/
Output signal circuit.
2.10.1 Safety Precautions
•
If you want to bypass the STO function, make sure the STO connector is plugged into CN4 on
the drive correctly.
•
When using the STO function, perform an equipment risk assessment to ensure that the system
conforms to the safety requirements.
•
Even when the STO function is enabled, the motor may move due to external force (e.g.
gravitational force on the vertical axis). Make sure a holding brake is used in applications where
this is possible.
•
When the STO function engages and the torque is removed, the motor will be “free running”,
requiring more distance until the motion stops. Make sure this will not be a safety issue.
• When the STO function operates, it will turn off the current to the motor, but it does not turn off
the power to the drive. Make sure to disconnect the power to the drive before performing any
maintenance on it.
•
After the STO function is triggered, the drive will have a fault alarm status, and the motor will
remain disabled even after the STO function switch is plugged back in. To restore the system to
normal operation, clear the fault alarm, and then enable the drive and motor.
2.10.2 STO Internal Circuit Diagram
SF1+
SF1-
SF2+
SF2-
EDM+
EDM-
1.5K
1.5K
2.10.3 CN4 Connector diagram
