Advanced commissioning
7.7 Safe Torque Off (STO) safety function
SIMATIC ET 200pro FC-2 converter
Operating Instructions, 04/2018, FW V4.7 SP10, A5E34257324B AF
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7.7
Safe Torque Off (STO) safety function
7.7.1
Description of functions
How does STO function?
The converter with active STO prevents machine
components from inadvertently starting.
Table 7- 13 The principle of operation of STO
Safe Torque Off (STO)
Standard converter functions linked with STO
1. The converter detects via the F0 rail that STO
has been selected.
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2. The converter prevents energy from being fed
to the motor. When STO is active, the motor
does not generate any torque.
If you use a motor holding brake, the converter
closes the brake.
3. The converter signals "STO is active".
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Figure 7-10 Principle of operation of STO when the motor is stationary and when the motor is rotating
If the motor is still rotating when STO is selected, then it coasts down to standstill.
The STO safety function is standardized
The STO function is defined in IEC/EN 61800-5-2:
