ABB ACS800-04 Hardware Manual page 52

52 Planning the electrical installation
The Safe torque off function can be used to stop the drive in emergency stop
situations. In the normal operating mode, use the Stop command instead. If the Safe
torque off function is activated when the drive is running, the control voltage of the
power semiconductors is cut off and the motor coasts to a stop. If this is not
acceptable, for example, causes danger, the drive and machinery must be stopped
using the appropriate stopping mode before using this function.
Note concerning permanent magnet motor drives in case of a multiple IGBT power
semiconductor failure: In spite of the activation of the Safe torque off function, the
drive system can produce an alignment torque which maximally rotates the motor
p p
shaft by 180/ degrees. denotes the pole pair number.
ACS800-
For more information on the STO function and the relevant safety data, see
01/04/11/31/104/104LC Safe torque off function (+Q967), Application guide
(3AUA0000063373 [English]).