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ABB Oy, Drives Service
Department
Date
ESP300
13.08.2018
2.3
Control unit replacement (CCU)
2.3.1 Safe torque off function STO
Safe operation of the STO must be verified after any changes and maintenance work related to the
safety function (circuit boards, wiring, components, settings, etc.). The acceptance test procedure is
described in section 2.3.2. More on STO and the Acceptance test procedure can be found in the
ACX580 User's Manual.
The drive supports the Safe torque off function according to standards EN 61800-5- 2:2007; EN ISO
13849-1:2008, IEC 61508, IEC 61511:2004 and EN 62061:2005. The function also corresponds to
prevention of unexpected start-up of EN 1037.
The Safe torque off function disables the control voltage of the power semiconductors of the drive
output stage, thus preventing the inverter from generating the voltage required to rotate the motor. By
using this function, short-time operations (like cleaning) and/or maintenance work on non-electrical
parts of the machinery can be performed without switching off the power supply of the drive.
WARNING! The Safe torque off function does not disconnect the voltage of the main and auxiliary
circuits from the drive. Therefore maintenance work on electrical parts of the drive or the motor can
only be carried out after isolating the drive from the main supply.
WARNING! (With permanent magnet motors only) In case of a multiple IGBT power semiconductor
failure, the drive system can produce an alignment torque which maximally rotates the motor shaft by
180/p degrees regardless of the activation of the Safe torque off function. p denotes the number of
pole pairs.
Notes:
•
If a running drive is stopped by using the Safe torque off function, the drive will cut off the
motor supply voltage and the motor will coast to a stop. If this causes danger or is not
otherwise acceptable, stop the drive and machinery using the appropriate stop mode before
activating the Safe torque off function.
•
The Safe torque off function overrides all other functions of the drive unit.
•
The Safe torque off function is ineffective against deliberate sabotage or misuse.
•
The Safe torque off function has been designed to reduce the recognized hazardous
conditions. In spite of this, it is not always possible to eliminate all potential hazards. The
assembler of the machine must inform the final user about the residual risks.
© Copyright 2018 ABB Oy. All rights reserved. Specifications subject to change without notice.
On-Site Service Instructions
ACx580-01 R0-R5
Document nbr
3AXD10000303478
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