Rockwell Automation 21G PowerFlex 750 Series Safe Torque Off - Manual (Page 27)

Rockwell Automation Publication 750-UM002F-EN-P - July 2013 27
Chapter
4
Description of Operation
PowerFlex 750-Series Safe
Torque Off Operation The PowerFlex 750-Series Safe Torque Off option module (see Figure 1 ) disables
the drive’s output IGBT’s by either disconnecting the power supply to the gate
control driver IC or disabling the output of the gate control driver IC. The
system satisfies the requirements of SIL3 for safe turn off of torque.
Under normal operation, 24V DC is applied to both the Safety Power and Safety
Enable inputs of the Safe Torque Off option module. If the Safety Enable or
Safety Power is de-energized, the outputs of the gate control driver IC are
disabled and IGBT firing is disabled. Parameter 933 [Start Inhibits] will indicate
that IGBTs are inhibited and the HIM will indicate that the drive is not enabled.
IMPORTANT The Safe Torque Off option does not eliminate dangerous voltages at the drive
output. Input power to the drive must be turned off and safety procedures
followed before performing any electrical work on the drive or motor.
ATTENTION: In the event of the failure of two output IGBTs in the drive, when
the PowerFlex 750-Series Safe Torque Off option has controlled the drive
outputs to the off state, the drive may provide energy for up to 180° of rotation
in a 2-pole motor before torque production in the motor ceases.
ATTENTION: By itself, the PowerFlex 750-Series Safe Torque Off option initiates
a coast-to-stop action. Additional protective measures will need to be applied
when an application requires a different stopping action.