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Rockwell Automation Publication SAFETY-AT140A-EN-P - May 2015
Safety Function: Actuator Subsystems – Stop Category 1 via the PowerFlex 525 and PowerFlex 527 Drives with Safe Torque-off
The sum response/reaction time of the Guardmaster dual-input safety relay, Guardmaster multifunction-delay expansion
module, Guardmaster multifunction-delay expansion module delay, and PowerFlex drive, and worst-case, coast-to-stop
portion of the overall system-stopping performance is the same regardless of the input device used.
It may be useful to estimate how fast the hazardous motion must coast to a stop before the safeguarded system is available
for testing.
The maximum safe coast-to-stop time for a system using the PowerFlex 525 drive can be calculated as follows:
SensaGuard switch (SG) + Guardmaster dual-input safety relay (GSR DI) + Guardmaster multifunction-delay
expansion module (GSR EMD) + Guardmaster multifunction-delay expansion module delay (EMDd) + PowerFlex
525 drive (drive) = overall system stopping performance less maximum safe coast-to-stop time
54 ms (SG) + 35 ms (GSR DI) + 35 ms (EMD) + 100 ms (EMDd) + 100 ms (drive) = 324 ms = overall system
stopping performance time less the estimated maximum safe coast-to-stop time
476 ms - 324 ms = 152 ms = estimated maximum safe coast-to-stop time
The maximum safe coast-to-stop time for a system using the PowerFlex 527 drive can be calculated as f ollows:
SensaGuard switch (SG) + Guardmaster dual-input safety relay (GSR DI) + Guardmaster multifunction-delay
expansion module (GSR EMD) + Guardmaster multifunction-delay expansion module delay (GSR EMDd) +
PowerFlex 527 drive (drive) = overall system stopping performance less maximum safe coast-to-stop time.
54 ms (SG) + 35 ms (GSR DI) + 35 ms (GSR EMD) + 100 ms (EMDd) + 12 ms (drive) = 236 ms = overall system
stopping performance time less the estimated maximum safe coast-to-stop time
476 ms - 236 ms = 240 ms = estimated maximum safe coast-to-stop time.
