Safety Cat. 3 Performance Definition; Stop Category Definitions - Allen-Bradley PowerFlex 7000 Series User Manual

Chapter 2 Safety Concept
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ATTENTION: The drive should never be considered in a safe state unless the
safety function is active.
ATTENTION: When designing your system, consider how personnel will exit
the machine if the door locks while they are in the machine. Additional
safeguarding devices may be required for your specific application.

Safety Cat. 3 Performance Definition

To achieve Safety Cat. 3 according to ISO 13849-1:2008, the safety-related
parts have to be designed such that:
• the safety-related parts of machine control systems and/or their
protective equipment, as well as their components, shall be designed,
constructed, selected, assembled, and combined in accordance with
relevant standards so that they can withstand expected conditions.
• basic safety principles shall be applied.
• a single fault in any of its parts does not lead to a loss of safety function.
• the average diagnostic coverage of the safety-related parts of the control
system shall be medium.
• the mean time to dangerous failure of each of the redundant channels
shall be high.
• measures against common cause failure shall be applied.

Stop Category Definitions

The selection of a stop category for each stop function must be determined by a
risk assessment.
• Stop Category 0 is achieved with immediate removal of power to the
actuator, resulting in an uncontrolled coast to stop. Safe Torque Off
accomplishes a Stop Category 0 stop.
• Stop Category 1 is achieved with power available to the machine
actuators to achieve the stop. Power is removed from the actuators when
the stop is achieved.
IMPORTANT When designing the machine application, timing and distance should be
considered for a coast to stop (Stop Category 0 or Safe Torque Off). For more
information regarding stop categories, refer to EN 60204-1.
Rockwell Automation Publication 7000-UM203C-EN-P - September 2018