Rockwell Automation Publication 2198-UM001I-EN-P - May 2019 171
Kinetix 5500 Safe Torque-off - Hardwired Safety Chapter 9
Description of Operation
The safe torque-off feature provides a method, with sufficiently low probability
of failure, to force the power-transistor control signals to a disabled state.
When disabled, or any time power is removed from the safety enable inputs, all
of the drive output-power transistors are released from the ON-state. This
results in a condition where the drive performs a Category 0 Stop. Disabling
the power transistor output does not provide mechanical isolation of the
electrical output that is required for some applications.
Under normal operation, the safe torque-off inputs are energized. If either of
the safety enable inputs are de-energized, then all of the output power
transistors turn off. The safe torque-off response time is less then 12 ms.
Figure 72 - System Operation when Inputs are Meeting Timing Requirements
ATTENTION: Permanent magnet motors can, in the event of two
simultaneous faults in the IGBT circuit, result in a rotation of up to 180
electrical degrees.
ATTENTION: If any of the safety enable inputs de-energize, the Start Inhibit
field indicates SafeTorqueOffInhibit and GuardStopRequestStatus bit of
AxisGuardStatus tag set to 1. Both inputs must be de-energized within 1
second and re-energized within 1 second to avoid GuardStopInputFault
conditions.
24V DC
24V DC
0V DC
0V DC
1
1
0
0
100 ms
1 Second
1
23 4
5
6
GuardStopRequestStatus
GuardStopInputFault
SS_IN_CH0
SS_IN_CH1
Event Description
1 At least one input is switched-off. GuardStopRequestStatus bit is set to 1.
2
Second input is switched-off within 1 second. This event must always occur prior to Event 3 to prevent
GuardStopInputFault.
3 First input is switched-on.
4 Second input is switched-on within 1 second of event 3.
5
Both inputs are in OFF state simultaneously within 1 second. As a result, GuardStopInputFault is not
posted.
6
The GuardStopRequestStatus bit sets back to 0 if event 4 occurs within a 100 ms interval after event 3. If
event 4 is outside of the 100 ms interval, but within the a 1 second interval after event 3, then the
GuardStop RequestStatus bit sets back to 0 after the 1 second interval following event 3 (not
immediately following event 4).
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