Function Description - Siemens Sinamics CU240D-2 DP Operating Instructions Manual

Advanced commissioning
6.11 Safe Torque Off (STO) safety function
6.11.1

Function description

What does the STO safety function do?
An inverter with active STO function prevents energy supply to the motor. The motor can no
longer generate torque at the motor shaft.
Consequently, the STO function prevents the starting of an electrically-driven machine
component.
Table 6- 16
1. The inverter recognizes the selection of STO
2. The inverter interrupts the energy supply to the
3. The inverter signals that "STO is active" via a
Figure 6-19
If the motor is still rotating (B) 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:
"[...] [The inverter] does not supply any energy to the motor which can generate a torque (or
for a linear motor, a force)."
⇒ The STO inverter function is in conformance to IEC/EN 61800-5-2.
The distinction between Emergency Off and Emergency Stop
"Emergency Off" and "Emergency Stop" are commands that minimize different risks in the
machine or plant.
150
The principle of operation of STO
Safe Torque Off (STO)
via a safety-relevant input or via the PROFIsafe
safe communication.
motor.
safety-relevant output or via the PROFIsafe
safe communication.
Functionality of STO when the motor is at standstill (A) and rotating (B)
Standard inverter functions linked with STO
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If you use a motor holding brake, the inverter
closes the brake.
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Converter with the control units CU240D-2
Operating Instructions, 04/2018, FW V4.9 SP10, A5E34262100B AF