Safe Torque Off - ABB MicroFlex e190 User Manual

44 Planning the electrical installation

Safe Torque Off

The drive supports the Safe Torque Off function according to standards
EN 61800-5-2; IEC 61800-5-2; EN 60204-1; EN 61508.
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 (see diagram below). 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 to the drive.
Control
circuit
Notes:
• The STO function is activated when one or both of the safety circuit contacts open. If the period
between both contacts opening or closing exceeds a predefined value, a fault in the safety circuit or
wiring is assumed and an error is reported. See
• The maximum cable length between the drive and the activation switch is 30 m (98 ft)
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 system from the main supply.
Note: It is not recommended to stop the drive by using the Safe Torque Off function. If
a running drive is stopped by using the Safe Torque Off function, the drive will stop by
coasting. If this is not acceptable (e.g. causes danger), the drive and machinery must
be stopped using the appropriate stopping mode before using this function.
For further information on the function, see
187.
MicroFlex e190
+24 V
Safe Torque Off
connection
UDC+
Output stage
(1 phase shown)
UDC-
Appendix: Safe Torque Off (STO)
Appendix: Safe Torque Off (STO)
X4:4
X4:1
X4:2
U/V/W
Activation
switch
on page 187.
on page