General
‑15‑
● The design of safety‑related systems requires specialist knowledge. To ensure the
safety of the entire control system, it is necessary to design the entire system
according to recognized safety rules. An individual subsystem with the STO
function, although intentionally designed for safety‑related applications, cannot
ensure the safety of the entire system.
● In emergency stop situations, the STO function can be used to stop the drive.
● In processes without personnel protection, do not to use the STO function to stop
the drive. If the STO function is used to stop a running drive, the drive will coast to
stop. If this is unacceptable, stop the system using a proper mode instead of the
STO function.
● This publication provides a guide on the application of Inovance STO function and
also on the design of safety‑related systems for machinery control.
● It is the responsibility of the designer of the end product or application to ensure
safety and compliance with relevant regulations.
Risk assessment
● Before using the safety function, perform risk assessment on the drive system in
advance to ensure compliance with the standard safety integrity level.
● The following residual risks can be present even when the safety function is
operating. Therefore, safety must always be considered during risk assessment.
● If external forces (such as gravity on the vertical axis) are applied when the safety
function is operating, the motor will rotate due to these external forces. In this
case, provide a separate mechanical brake to secure the motor.
Note
● When multiple faults occur on the IGBT power transistor, the drive will produce an
aligning torque regardless of whether the STO function is used. This torque may
drive the motor shaft to rotate to a maximum angle of (180 ÷ p).
● p indicates the number of motor pole pairs.
To guarantee safety, users must determine all the assessed risks and residual risks of
the integrated equipment. Companies and individuals that establish safety‑related
systems must be solely responsible for system installation and commissioning. In
addition, relevant sub‑systems subject to the European Machinery Directive must be
certified against safety standards, and risks and safety levels must be assessed for the
machine or the entire system.
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