BMR SFU 0303, Manual

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SFU 0303 Frequenzumrichter
7.9 Safe Torque Off (STO)
As an alternative to the "Single-channel safe pulse inhibit category3 EN954-1" in 7.8, the two-channel
function "Safe Torque Off" Safe Torque Off (STO) is also available.
Safe Torque Off (STO) is a safety function to prevent unexpected start-up according to EN 60204-1.
The STO function prevents the motor from generating torque and thus corresponds to stop category 0
as specified in IEC 61800-5-2.
Here, the output stage of the inverter can only be enabled by synchronously applying a +24V level to
the STO-A and STO-B inputs.
Feedback on the status of the STO is provided via the display of the control unit ("STO ImpLock" / "STO
Error "), at the status LEDs and via the STO feedback contact X5.1/X5.2 at connector X5 ( chap. 6.4 /
7.9).
Function and application
- Function "Safe Torque Off" (STO)
- Potential-free feedback contact for the operating status
Description of the STO safety function
By using the "Safe Torque Off" function (STO Safe Torque Off), the pulse control to the motor can be
interrupted in the application so that it can no longer execute torque or rotary motion.
The STO safety circuit is implemented in the SFU0303 as follows:
The control signals to the output stage are routed via optocouplers. When the STO function is
triggered, the power supply to the optocouplers is interrupted twice. This interrupts the isolating point
to the output circuit and no output pulses can be generated.
The drive can therefore no longer execute any dangerous movements.
The two control inputs STO-A and STO-B are used to request the STO safety function on two channels.
The two channels are potential-free to the inverter and also to each other and protected against
polarity reversal.
STO Safety hints
→ The STO state does not guarantee protection against electric shock
→ If the STO is triggered during operation, the output stage is deactivated immediately. A rotating
spindle can no longer be braked and will slowly coast to a stop .
This means that a certain amount of time passes until the drive no longer performs a dangerous
movement and the safe state is reached.
→ Monitoring whether or when the drive reaches the safe state is not integrated..