Rockwell Automation 21G PowerFlex 750 Series Safe Torque Off - Manual (Page 7)

Rockwell Automation Publication 750-UM002F-EN-P - July 2013 7
Chapter
1
General Description
The Safe Torque Off option is just one component in a safety control system.
Components in the system must be chosen and applied appropriately to achieve
the desired level of operational safety.
What Is the PowerFlex 750-
Series Safe Torque Off
Option? The PowerFlex 750-Series Safe Torque Off option:
• Is designed to help safely remove power from the gate firing circuits of the
drive’s output power devices (IGBT’s). This helps prevent the drive’s
output power devices from switching in the pattern necessary to generate
AC power to the motor.
• Can be used in combination with other safety devices to satisfy the
requirements of IEC 61508, IEC 61800-5-2 SIL 3, ISO 13849-1 PL e, and
Category 3 for Safe Torque Off (STO).
IMPORTANT This option is suitable for performing mechanical work on the drive system or
affected area of a machine only. It does not provide electrical safety.
This option should not be used as a control for starting and/or stopping the
drive.
ATTENTION: Electrical Shock Hazard. Verify that all sources of AC and DC power
are deenergized and locked out or tagged out in accordance with the
requirements of ANSI/NFPA 70E, Part II.
ATTENTION: To avoid an electric shock hazard, verify that the voltage on the
bus capacitors has discharged before performing any work on the drive.
Measure the DC bus voltage at the +DC and -DC terminals or test points (refer to
your drive’s User Manual for locations). The voltage must be zero.
ATTENTION: In safe-off mode, hazardous voltages may still be present at the
motor. To avoid an electric shock hazard, disconnect power to the motor and
verify that the voltage is zero before performing any work on the 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.