Safe Torque Off (Sto) Function - Omron OMNUC G5 User Manual

7-1 Safe Torque OFF (STO) Function

7-1 Safe Torque OFF (STO) Function
Outline of Operation
The safe torque OFF (hereinafter referred to as STO) function is used to cut off the motor
current and stop the motor through the input signals from a safety equipment, such as a Safety
Controller or safety sensor, that is connected to the safety connector (CN8).
When the STO function is operating, the driver turns OFF the servo ready completed output
(READY) to go into the safety status.
When using the STO function, be sure to execute a risk assessment of the equipment to confirm
that the system safety requirements are met.
There are following risks even when the STO function is operating. Be sure to take safety into
account as part of the risk assessment.
7
The EDM output signal is not a safety output. Do not use it for purposes other than the failure
monitoring function.
The dynamic brake and external brake release signal output are not safety-related parts.Make
sure that the equipment does not become dangerous during system design even if the external
brake release fails during the STO status.
When using the STO function, connect an equipment that meets the safety standards.
The PFH value is 2.30 × 10
7-1
Safty Points
• The motor runs if external force is present (e.g., force of gravity on the vertical axis, etc.). If
holding is required, implement appropriate measures, such as providing external brakes. Take
note that the brakes for the driver with brakes are used for the holding purpose only, and
cannot be used for control.
• Even if there is no external force, when Stop Selection for Alarm Generation (Pn510) is set to
free-run (with the dynamic brake disabled), the motor operates as free-run and the stop
distance is long.
• The motor may operate in the range of up to 180 degrees of electrical angle due to a power
transistor trouble and so forth.
• The power supply to the motor is cut off by the STO function, but the power supply to the driver
will not be cut off nor electrically insulated. For driver maintenance, cut off the power supply to
the driver through another means.
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OMNUC G5-SERIES AC SERVOMOTOR AND SERVO DRIVE USER'S MANUAL
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