autoreset plc Mitsibishi Q restart automatic

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At one of our plants we have problem with Mitsibishi Q (Q26UDEH)
The PLC reset automatically by itself for unknown reason. The failure of the PLC causes a disruption in our production process.
I have make  a counter in the software for counting the first-scan system bit voor analysing.
I have exchanged the CPU, power supply, and basic rack, but the plc keeps starting up automatically.
Does anyone have suggestions for solving this problem.

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Monitor your PLC power supply. If there ia a spike or some sort of transient this can cause the system to shutdown and restart.

May help, worth considering. have changed out the key components, and you still have the issue. It could be one of the other modules on the rack, networking module or analogue module would be the units to look at first. If one of these units are pulling the rack supply down, this will also give you the issue you describe.

Also, if you have a large volume of VSD's in your plant you may be producing a high 5th harmonic. You need reactors on the incoming of the VSD units in question to

reduce the system harmonic. EMC ration from VSD units in close proximity to the PLC can sometime cause issues such as described.





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Hi Anootje,

I suggest you place a temporary UPS in the 230Vac powerline to the CPU to investigate if the problem is caused in the powerline or in the PLC board itself.

This has two advantages:

1) you can check for external powerfail to your CPU. If the incomming power is interrupted you won't have a problem with it.

2) An UPS also has filters for harmonic spikes etc. (UPS clean line out)

Best regards,

Theo V.

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Thanks for thinking along with me

@ Colandra

I cannot find strange results by measuring (scope) the 220V supply. This plant contains a plc with a total of 19 intelligent modules (14p Q68ADI 4p Q68DAIN 1p Profibus.) .

The base and the 4 extension racks I have also renewed. A whole ago I got a error in a Q68ADI which even is renewed.



I already installed a ups s soon as this problem started. Even the Q61p power supply is replaced with a Q64PN (8.5A). The the problem remains

Best regards,



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