I have a message NST on ATV312 4KW, Drive is 2-wire control. When logic input=1 the drive is not working. When power off and on (restart) the logic input again the drive works normally.
There are few possible reasons for the drive to show "NST"
1. "NST" is the status of drive and it is not a fault. 2. If the drive is configured as 3 - wire configuration and the stop command "NC" push button is not connected to LI1. 3. If the drive is configured as 2 - wire or 3- wire configuration and the start command is present(high) at drive terminal during drive power up, it will show "NST". The drive can be powered off and remove the start command and power on the drive. The drive Run command should be given after the drive show "RDY" state. 4. As per customer's comment, the drive is working if they give the run command form "RDY" state. It means, there is no problem with drive, it is only programming and operational problem.
If the drive 2-wire control type = Transition (trn) and the start command is present during drive power ON, the drive will lock on "NST". It will require to switch off and ON the run command to start the drive. This is to avoid accidental running of drive during power resume after a power failure.
If you want automatic restart during the drive power ON after a power failure, this is only possible for the "2-wire" "level" control type ([2/3 wire control] (tCC) = [2 wire] (2C) and [2 wire type] (tCt) = (Level - LEL).