Safe torque off (STO) is a restart lock safety feature that prevents a system restart. The STO input provides direct electrical control of the power stage of the AKD drive. It bypasses the processor and will disable the power stage regardless of software or other hardware signals.
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- Brakes are controlled by firmware. If a brake needs to be applied when STO drops without using a controlled stop, then an external safety relay must be added in-line with the motor brake.
AKD-x003 up to AKD-x024
STO is controlled by a digital input which releases the power output stage of the drive as long as a 24 V signal is applied to the input. If the STO input goes open-circuit, then power will no longer be supplied to the motor, and the drive will lose all torque and coast to a stop. If the STO digital input does not have 24V applied to it and you attempt to enable the drive (using the hardware and software enables) the drive will generate a 602 “Safe Torque Off” fault.
AKD-x048
STO is controlled by two digital inputs which release the power output stage of the drive as long as a 24 V signal is applied to these inputs. If one of the STO inputs goes open-circuit, then power will no longer be supplied to the motor, and the drive will lose all torque and coast to a stop. If one of the STO digital inputs does not have 24V applied to it and you attempt to enable the drive (using the hardware and software enables) the drive will generate a 602 “Safe Torque Off” fault.
AKD-C Global STO
There is one STO-Enable input and one STO-Status output for each DC Power string. STO-Enable 1 only effects string 1. STO-Enable 2 only effects string 2.
The string STO input releases the power output stage of all AKD-N (without option DS) connected to the string as long as a 24 V signal is applied to this input. If the STO input goes open-circuit, then power will no longer be supplied to the connected motors, and the drives will lose all torque and coast to a stop.
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In case of using an AKD-N with option "DS" (local STO input), the global STO signal will have no influence on this drive. The local STO input on the AKD-N has no influence over the global STO. The local STO functionality is described in the AKD-N installation manual.
STO Fault
If you see this fault you need to apply 24V to the STO input and then clear the fault (DRV.CLRFAULTS ) before you can enable the drive. The STO will not generate a fault until you try to enable the drive. You can read the current faults using DRV.FAULTS.
-->DRV.FAULTS
602: Safe torque off.
-->
Reading STO state
The current state of the STO can be read using the STO.STATE parameter. WorkBench shows you the state of the STO inputs in the status bar at the bottom of the window.
