STO special circumstances
A short circuit between two non-adjacent IGBTs in a short period of time can cause the
movement to reach 120 electrical degrees, even if STO function takes effect. The probability of such
an event is extremely low, but it could still happen. However, the probability of such fult is
considered negligible.
9.6 STO Maintenance
Users must perform manual testing of STO functionality at least once every three months.
The diagnostic test needs to remove the STO power supply voltage and verify that the drive is
really in the STO fault state and that the movement is prohibited.
Maintenance procedures are performed as follows:
The system is set up to provide nominal STO voltage to the drive and the drive is enabled.
◼ The drive is in a fault state and displays an STO fault.
◼ The drive cannot be enabled.
2. Restore STO voltage and clear the fault. Verify that the drive is enabled.
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