Power outage of the inverter caused an alarm on the Yokogawa CS3000 AO card (AAI5430); redundant cards were switched in
Thread Content
The fault is roughly as follows: The 4-20mA signal generated by the AO card (AAI543) of the Yokogawa CS3000 is sent to the frequency converter in the MCC through the safety relay MTL4546Y. To repair the pump, it was necessary to shut down the power supply supplied by the electrical department; after the electrical department turned off the power to that frequency converter, the AAI543 card started to give alarms, and a switchover to the redundant card took place (the primary card was replaced by the backup card). The solution was to install an ECT isolator between the safety barrier and the frequency converter, after which the fault symptom disappeared. I would like to ask everyone: does the MTL4546Y safety barrier not provide isolation? What are also the causes of Cheka (preferably more specific)? Is an intrinsically safe barrier of the Zener type or an isolation type? How can I tell the difference? (I’m a bit confused.) Thank you all! ! !
Is the 4546Y three-terminal isolated device with line detection damaged?
Based on what you’ve described, I personally think it’s not due to a fault caused by isolation; rather, it seems to be a result of switching triggered by the circuit OOP. It’s possible that your original safety gate did not have this function, and when there was a power outage in the inverter, the circuit became open, which led to the mistaken assumption that the AO card was also open, thereby triggering the switch
It doesn’t seem to be the case, because for example, with a card that is also AAI543, if the connection to the on-site control valve is severed, an OOP alarm will be triggered at that point, but it won’t cause an alarm related to the card itself. How can this be explained?
Is the output card of the control valve also redundant?
Well, our output cards are all redundant
With the Yokogawa VP system used in our company, sudden OOP open-circuit errors have occurred whenever the AO signal was sent to variable frequency drives and on-site pneumatic control valves; this has led to locking of the cards and redundancy-related issues. Yokogawa attributes these problems to excessive load in the circuit or the presence of interference voltages. For now, we can only continue to monitor the situation, as no better solution has been proposed.
Today, our card failed to perform the cut-off operation, which resulted in no output from the safety barrier