Together with a suitable safety relay unit, the following can be achieved:
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Safe stop 1 time controlled Safe stop 1 time controlled; triggering of motor deceleration and, after
an application-specific time delay, triggering of the safety function STO
Requirements of SS1
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Wiring for safety function STO
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Execute emergency stop command by means of the safety relay unit (either directly by wiring
CTRL-EN or indirectly via a further functional controller).
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The time for executing an emergency stop is known.
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The safety relay unit supports programmable timers and simple logic elements.
Function and application of SS1
The procedure for triggering SS1-t comprises the following steps:
1. Requesting a functional emergency stop (e.g. set input CTRL-EN to low signal).
This causes the servo drive to trigger a braking ramp function and – if present – allows the brake
function to engage at the end of the braking ramp. After completing the braking ramp and upon
elapse of the parameterisable delay time until the brake is closed, the output stage is switched off
functionally.
2. Start of a time-delay element for actuation of STO.
Select the delay time such that the functional braking ramp is completed in closed-loop control,
the holding brake function is engaged, and the output stage is switched off functionally. Other-
wise, simultaneous triggering of STO and the mechanically required brake engagement time can
cause the axis to sag. If the brake is engaged while the axis is still in motion, there is increased
wear on the holding brake (only permitted for emergency braking).
3. Request for safety function STO and – if required – additionally SBC upon elapse of the delay time.
The figure below shows the necessary logic circuit for the safety relay unit:
Logic in the safety relay unit for SS1
Product overview
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Festo — CMMT-AS-...-S1 — 2018-02