A Cat3 safety circuit is supposed to detect any single fault. To check the safety contactors, we normally connect the contactor feedbacks to the safety relay. In the safety parlance, this is called EDM (External Device Monitoring).
When using a VFD (one with safe-off functionality), we should use the same approach. With a PowerFlex 40P or 70, there is such a feedback (TB 1-2 of safe-off board).
However, with the PowerFlex 525, the feedback is not available.
First, his means that a 525 cannot be used as a replacement for a 40P.
Since the drive is certified for Cat3, does it mean that the safe-off circuit is considered to be infallible?
When using a VFD (one with safe-off functionality), we should use the same approach. With a PowerFlex 40P or 70, there is such a feedback (TB 1-2 of safe-off board).
However, with the PowerFlex 525, the feedback is not available.
First, his means that a 525 cannot be used as a replacement for a 40P.
Since the drive is certified for Cat3, does it mean that the safe-off circuit is considered to be infallible?
