Safety Function
‑80‑
7 Safety Function
7.1 Safety Function Overview
The Safe Torque Off (STO) function immediately blocks the motor torque or power
output in electronic mode according to input signals STO1 and STO2 from external
devices. This function complies with stop category 0 in EN 60204‑1.
If the motor is still rotating when the STO function is enabled, the motor will coast to
a standstill.
7.2 Parameter Settings
The safety function module involves the following parameters.
Para.
No.
Name
Value Range Default Value
Description
F9‑79 STO
restoration
mode
0: Manual
reset
1: Automatic
reset
1: Automatic
reset
When both STO1 and STO2 are
disconnected, the system enters the
STO enabled state.
When STO1 and STO2 are restored,
the system enters the servo ready
state depending on the value of this
parameter.
7.3 STO
7.3.1 Overview
Safe Torque Off (STO) is a safety function that complies with IEC 61800‑5‑2:2016. This
AC drive is integrated with the STO function. After the STO function is enabled, the AC
drive switches off the servo ready (RDY) signal and enters the safe state. At the same
time, the drive control signal of the power semiconductor is blocked and the input
motor current is cut off to prevent the AC drive from generating the torque at the
motor shaft end to make the motor stop operating.
The STO function blocks the output of PWM signals to the power layer of the AC drive
through external redundant hardware terminals STO1 and STO2, preventing the
movement of the motor. The two +24 VDC signals must be active (high level) to
enable normal operation of the AC drive. If either or both of them are at low level
simultaneously, the PWM signal will be blocked.
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