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8 Safety Function
8 - 2
AC Servomotors/Servo Drives 1S-series with Built-in EtherCAT® Communications User’s Manual (I586)
8-1
Safe Torque OFF Function
The Safe Torque OFF (STO) function is used to cut off the motor current and stop the motor through the
input signals from a safety controller.
When the STO function is activated, the Servo Drive turns OFF the Servo Ready Output (READY) and
enters the safe state.
The 1S-series Servo Drives have the following two types of STO functions. Use either of these func-
tions according to your safety device configuration.
• STO function via safety input signals
• STO function via EtherCAT communications
The PFH value of the 1S-series Servo Drives is as follows.
Precautions for Correct Use
On setting
• Before you execute downloads and restoration, check that the equipment does not operate.
• When downloads and restoration are completed, conduct the user test before system opera-
tion to make sure that all safety devices operate correctly.
On replacement
• A Servo Drive before replacement must have the factory default condition. If you are not sure
that the Servo Drive has the factory default condition, initialize the parameters for the Servo
Drive after replacement.
• When you replace a unit, make sure that the unit model is correct, the mounting positions of
the unit and terminal blocks are correct, and the unit is properly configured and operates as
intended.
On conducting test run
• When you use Sysmac Studio to perform a test run without EtherCAT cable connection, the
STO function via EtherCAT communications is disabled temporarily. If you need the STO
function during this type of test run, use the STO function via safety input signals.
On use of STO function
• When you use 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.
• 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 Servomotor with brakes are used for holding only, and cannot be used for
control.
• Even if there is no external force, when
Stop Selection - Shutdown Option Code
(3B20-01 hex) is set to free-run with the dynamic brake disabled, the motor uses free-run
stopping and the stop distance is long.
• In case of internal failure of components such as the power transistor, the motor may oper-
ate in the range of up to 180 degrees of electrical angle.
• 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. When you conduct Servo Drive
maintenance, cut off the power supply to the Servo Drive through another means.
STO function
PFH [1/h]
STO function via safety input signals
2.0 x 10
-11
STO function via EtherCAT communications 1.6 x 10
-9
Summary of Contents for R88D-1SN ECT Series
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