User Manual - Series B Instruction Manual

Rockwell Automation Publication PFLEX-UM003B-EN-P - July 2012 19
Description of Operation
PowerFlex 70 Safe Torque Off Operation
The PowerFlex 70 DriveGuard Safe Torque Off option (see Figure 9) disables
the drive’s 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. Refer to 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 O Option
PFLEX-UM003.fm Page 19 Wednesday, July 18, 2012 8:26 AM