Fried two modules, whats happening?

[CumuluNimbus]

Hi

Replaced an faulty AI module (331-7KF02-0AB0).
When Inputs connected smoke was rising from the card. Got afraid of sinking the whole node so I disconnected quickly. Messured everything and it looks normal, except from one of the frequency converter that had no base 24v out from its RAIO.
Suspected that drive, drisconnected it from the inputs and put in a new module.
Same thing again. Burnt smell and smoke.
The orignial module had the "blocks" set to C, 4-wire input. So I did configure the replacement modules the same.

ACS 800, current and speed via RAIO, 4-20.


Any ideas?

 

[BryanG]

Best guess would be that there is a large voltage difference between the zero volts on the PLC and the VSD. So either bond the zero volts together or add 4-20mA loop isolators.

When you get the blue smoke it means there is a voltage difference that shouldn't be there, or there is too much current flowing. Measure the voltage between the two zeros, measure the current flowing in the 4-20mA loops, and check for any difference in earth voltages.

 

[JesperMP]

Suspected that drive, drisconnected it from the inputs and put in a new module.
Same thing again. Burnt smell and smoke.

You suspected the drive, disconnected it from the analog input, replaced the analog module, and connected the drive again.
Despite that you suspect the problem is not with the analog input, you didn't do anything, other than replacing the analog input.
If the above is correct, then of course you will burn the replaced analog input.

Disconnect the wires from the drives.
Measure Amps between the wires from the drive. You shall only get a signal between 4-20mA.

Messured everything and it looks normal, except from one of the frequency converter that had no base 24v out from its RAIO

Why should there be a 'base 24V' from an analog output ?
There should be no 24V in any of the wires from the drive to the PLC analog input.

Another problem can be voltage difference, but that would zap the input rather than burn it.
Is the drive grounded correctly ?
Are there a long distance between drive and PLC ?

Post a sketch of all the wiring between the drive and the PLC.

 

[arpus4KM]

typically for too much current flowing through an analog input, you don't have a good loop.

make sure any power supplies are grounded or at the same potential, and double check where wiring is coming from. if you are hooking up between two things in a loop and there is more current draw than expected, then you may have leakage through another path or potential difference is too great between lines.

These are just guesses, I would always start with the basics and ensure everything is wired correctly and all voltages are what I think they are.


Do you have a loop simulator you can test the card with before hooking the drive up? and do you have another drive you can test in place of the current one that may be causing an issue? I can't tell if you just put a new card in and it smoked again, or you hooked up the supposedly faulty drive and it smoked again.

 

[PLCDontUQuitOnMe]

Is it possible the drive AO is configured for current (0-20ma) and the AI card channel is configured for voltage?



In that case the AO of the drive is going to keep increasing voltage until it sees the current that it is trying to output. If the AI card is set for voltage input, the resistance of the input will be much higher than if set for current input, so the drive could be increasing voltage beyond what the card is capable of receiving, as it tries to force a certain amount of current through the loop that the card is not allowing due to the configuration difference.



Worth a check.