QSHT 5700 Inverter Safe Torque-off Function
Hardwired Safe Torque-off
QuickStick HT User Manual 269
Rockwell Automation Publication MMI-UM007F-EN-P - September 2020
Hardwired Safe Torque-off
This section introduces the QuickStick HT 5700 inverter hardwired safe torque-off (STO) fea-
ture that meets the requirements of Performance Level e (PL e) per ISO 13849-1 and SIL CL
3 per IEC 61508, IEC 61800-5-2, and IEC 62061.
The MMI-HT-C2198-D032 inverter uses the STO connector for wiring external safety
devices and cascading hardwired safety connections from inverter-to-inverter.
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 STO inputs, all of the QSHT 5700 inverter output-power transis-
tors are released from the ON-state. This results in a condition where the inverter performs a
Category 0 Stop (see Stop Category Definition on page 264).
For hardwired control of the safe torque-off (STO) function the appropriate wiring must be
connected to the Safety (STO) connector plug. See Hardwired Safe Torque-off Electrical
Specifications on page 279 for more information on the safety inputs.
Falling of suspended or inclined loads, or a stopped position where one end of the vehicle
magnet array is engaged by the coils in a stator but the other end is not creates potential
energy that could result in unintended motion. In these cases, the force from gravity acting on
the load, or the asymmetric force from magnetic attraction between the magnet array and the
stators, can cause motion. Note that these scenarios are in effect without cause from any sort
of system failure.
Under normal operation, shown in Figure 7-1 and described in Table 7-3, the safe torque-off
inputs are energized. If either of the STO inputs are de-energized, then all of the output power
transistors turn off and both axes will fault with the same error. The safe torque-off response
time is less than 12 ms.
ATTENTION: Disabling the power transistor output does
not provide physical isolation of the electrical output that is
required for some applications.
ATTENTION: In circumstances where external influences
(for example, falling of suspended or inclined loads, or a
stopped position where one end of the mover magnet array is
engaged by a stator but the other end is not) are present, addi-
tional measures (for example, mechanical brakes) are neces-
sary to prevent any hazard.
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