Metronix smartServo BL 4000-C Series, Руководство по эксплуатации продукта

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8 STO (safe torque off)
8.5 Principle of operation and use
The STO function includes the feature "Realisation of the "Safe Torque Off" (STO)
function".
The "Safe Stop 1" (SS1) function can be realised with a suitable external safety relay and
by suitable wiring of the servo drive.
8.5.1 Description of the STO safety function
Use the "Safe Torque Off" (STO) function if you need to disconnect the motor safely from
the energy supply for your application. The "Safe Torque Off" function switches off the
driver supply for the power semiconductors. This prevents the power output stage from
providing the voltage that is required by the motor. As a result, the motor cannot start
unexpectedly. See the following illustration.
Figure 117: "Safe Torque Off" - principle of operation
When the "Safe Torque Off" (STO) function is active, the energy supply to the drive is
interrupted in a safe manner. The drive can neither generate any torque nor any dangerous
movements. In the case of suspended loads or other external forces, additional measures
must be taken in order to prevent the load from sagging (e.g. mechanical holding brakes).
In the "Safe Torque Off" (STO) state, the standstill position will not be monitored.
Risk of a jerky movement of the drive in the case of multiple errors
If the output stage of the servo drive fails while in the STO state (simultaneous short
circuit of 2 power semiconductors in different phases), a limited dwell movement of the
rotor may result. The angle of rotation/distance corresponds to one pole pitch.
Examples:
l
Rotary axis, synchronous machine, 8 poles
è
movement < 45° of the motor shaft.
l
Linear motor, pole pitch 20 mm
è
movement < 20 mm of the moved part.
Product manual BL 4000-C Page 196 of 298