Rockwell Automation Publication 2198-UM001I-EN-P - May 2019 179
Kinetix 5500 Safe Torque-off - Integrated Safety Chapter 10
Stop Category Definition
Stop Category 0 as defined in IEC 60204 or safe torque-off as defined by
IEC 61800-5-2 is achieved with immediate removal of motion producing
power to the actuator.
Performance Level (PL) and Safety Integrity Level (SIL)
For safety-related control systems, Performance Level (PL), according to ISO
13849-1, and SIL levels, according to IEC 61508 and IEC 62061, include a
rating of the systems ability to perform its safety functions. All of the safety-
related components of the control system must be included in both a risk
assessment and the determination of the achieved levels.
Refer to the ISO 13849-1, IEC 61508, and IEC 62061 standards for complete
information on requirements for PL and SIL determination.
Description of Operation
The safe torque-off (STO) feature provides a method, with sufficiently low
probability of failure, to force the power-transistor control signals to a disabled
state. When the command to execute the STO function is received from the
GuardLogix controller, all of the drive output-power transistors are released
from the ON-state. This results in a condition where the drive is coasting.
Disabling the power transistor output does not provide mechanical isolation of
the electrical output that is required for some applications.
The 2198-Hxxx-ERS2 drive STO function response time is less than 10 ms.
Response time is the delay between the time the drive STO function receives
the integrated safety packet with an STO request and the time when motion
producing power is removed from the motor.
STO State Reset
The 2198-Hxxx-ERS2 servo drives support both manual and automatic restart
types for exiting the STO state.
• Manual restart indicates a transition from 0 to 1 on the SO.Reset tag
is required to allow torque after the SO.SafeTorqueOff tag has
transitioned from 0 to 1.
• Automatic restart indicates torque will be allowed only by
transitioning the SO.SafeTorqueOff tag from 0 to 1. The SO.Reset
tag is used only for resetting safety faults.
IMPORTANT In the event of a malfunction, the most likely stop category is Stop Category
0. When designing the machine application, timing and distance must be
considered for a coast to stop. For more information regarding stop
categories, refer to IEC 60204-1.
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