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Rockwell Automation Publication PFLEX-UM003D-EN-P - June 2021
Description of Operation
PowerFlex 70 Safe Torque Off Operation
The PowerFlex 70 DriveGuard Safe Torque Off option (see
output IGBT’s by disconnecting the gate control power supply. When used in
combination with a second safety channel (the Enable input), the system satisfies the
requirements of EN ISO 13849-1, Category 3 / PL (d) for Safe Torque Off and helps
protect against restart.
Under normal drive operation, the Safe Torque Off relay is energized, the enable input
is energized, and gate control power is available to the gate control circuit. If either of
these inputs is de-energized, the gate control circuit is disabled. To meet EN ISO
13849-1, Category 3 / PL (d) operation, both safety channels must be de-energized. See
the following examples for details.
Figure 9 - PowerFlex 70 Drive Safe Torque Off Circuitry
IMPORTANT
By itself, the Safe Torque Off option initiates a coast-to-stop action.
Additional protective measures will need to be applied when an application
requires a change to the stop action.
+24V DC
PowerFlex 70
AC Drive
Stop
Start
AC Line
Input Power
Common
Enable
M
Gate Control
Power Supply
Gate Control
Circuit
Safety
Channel
Safety
Channel
1
2
3
4
Safe Off Option
