Festo — CMMT-ST-C8-1C-...-S0 — 2021-04b
Product overview
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Additional information
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Contact the regional Festo contact if you have technical problems
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Product overview
4.1
Safety sub-functions
4.1.1
Function and application
The servo drive CMMT-ST-...-S0 has the following safety-related performance features:
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Safe torque off (STO/Safe torque off)
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Safe stop 1 time controlled (SS1-t/Safe stop 1 time controlled) with use of a suitable external safety
relay unit and appropriate servo drive circuitry
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Diagnostic contact STA for feedback of the active safety sub-function STO
4.1.2
Safety sub-function STO
Fig. 1: Symbol for STO
The function described here implements the safety sub-function STO according to EN 61800-5-2
(corresponds to stop category 0 from EN 60204-1).
The safety sub-function STO is used when the power supply to the motor needs to be switched off
safely in the application but there are no further requirements for a targeted standstill of the drive
(such as stop category 1 from EN 60204-1
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Safety sub-function SS1-t).
Function and application of STO
The safety sub-function STO switches off the driver power supply for the power semiconductor, thus
preventing the power output stage from supplying the energy required by the motor. The power supply
to the drive is safely disconnected when the safety sub-function STO is active. The drive cannot
generate torque and so cannot perform any dangerous movements.
With suspended loads or other external forces, additional measures must be put in place to prevent
movements being performed (e.g. mechanical clamping units). In the STO state, the standstill position
is not monitored.
The machines must be stopped and locked in a safe manner. This especially applies to vertical axes
without automatic locking mechanisms, clamping units or counterbalancing.
