Rockwell Automation Publication 7000-UM203C-EN-P - September 2018
15
Chapter
3
Operation, Installation, and Wiring
PowerFlex 7000 Drive Safe
Torque Off Operation
The PowerFlex™ 7000 Drive Safe Torque Off option disables the rectifier and
inverter SGCTs by removing the power supply to the fiber optic transmitters
that command the devices to turn on, and disabling the gating signals to those
fiber optic transmitters. The system satisfies the requirements of SIL3 for safe
turn off of torque.
Figure 1
shows the block diagram of the STO option in the
PowerFlex 7000 drive.
The Safe Torque Off option is intended to be part of the safety related control
system of a machine. Before installation, a risk assessment should be performed
that compares the Safe Torque Off option specifications and all foreseeable
operational and environmental characteristics of the machine to which it is to
be fitted.
A safety analysis of the machine section controlled by the drive is required to
determine how often the safety function should be tested for proper operation
during the life of the machine.
The STO option is available in two types. The 24STO option is installed
during manufacturing of the drive and is intended for new drives. The
24STORK retrofit option is intended for existing drives and is located on the
LV Door (see
STO System Components Location on page 25
) and must be
installed by Rockwell Automation.
ATTENTION:
The following information is merely a guide for proper
installation. Rockwell Automation, Inc. cannot assume responsibility for the
compliance or the noncompliance to any code, national, local or otherwise
for the proper installation of this equipment. A hazard of personal injury and/
or equipment damage exists if codes are ignored during installation.
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:
There is a residual risk associated with four or more failures of
SCGTs within the drive that would cause torque to be developed even when
the PowerFlex 7000 Drive Safe Torque Option has controlled the drive outputs
to the off state. In this case, the drive may provide energy until the published
response time of 1000 ms has expired.
Summary of Contents for PowerFlex 7000 Series
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