Safe Torque Off (Sto) Function - Omron R88M-K Series 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 according to IEC61800-5-2) 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 Servo Drive turns OFF the servo ready completed
output (READY) to go into the safety status.
 The PFH value is 2.30 × 10
 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 the following risks even when the STO function is operating. Be sure to take safety into
account as part of the risk assessment.
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 The EDM output signal is not a safety output. Do not use the EDM output for any purpose other
than the failure monitoring function.
 Be sure to check the wiring when installing. Especially check the following:
 The system with incorrect wiring may damage the safety function.
 The dynamic brake and external brake release signal outputs are not safety-related parts. Make
sure to design the equipment so that it is not dangerous even if the external brake release fails
during the STO status.
 When using the STO function, connect equipment that meets the safety standards.
 Following certifications are fulfilled:
7-1
−8
Precautions for Safe Use
• The motor runs if an external force is present (e.g., force of gravity on a vertical axis). If holding
is required, implement appropriate measures, such as providing external brakes. The brakes
for a Servo Drive 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 Detection (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 Servo
Drive will not be cut off nor electrically isolated. For Servo Drive maintenance, cut off the power
supply to the Servo Drive through another means.
• The wiring is not short-circuited or disconnected.
• The polarity of EDM circuit is not reversed.
• SF1, SF2 and EDM operate properly.
• CAT-3 (EN 954-1, EN/ISO 13849-1)
• Performance level d (EN/ISO 13849-1)
• SIL 2 (IEC/EN 62061)
OMNUC G5-SERIES AC SERVOMOTOR AND SERVO DRIVE USER'S MANUAL
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