Background: Due to the requirements of environmental protection, diesel engine-driven tire cranes have undergone a technical transformation of oil-to-electricity conversion in the past few years, that is, the use of mains power in the field and the use of diesel engines in the field. Therefore, two plc electrical sites are added on both sides of the cart, and the status of the electric carts on both sides is collected and transmitted to the main PLC (S7-400) through ET200M. When the cart is walking, it does not avoid collision with the trolley wire (feeder). Several limit positions are set on the electric trolley, and the movement of the cart is controlled through a series of limit state interlocks.
Process: One day, the site reported that a tire crane truck could not move, and the BF light of the ET200M in the control cabinet on the side of the truck was flashing red, and the BF light on the side was steady red. The preliminary judgment was a communication failure, that is, the following troubleshooting was carried out: 1. Replace the communication plugs on both sides and the main PLC, 2. Replace the ET200M module, and the failure cannot be eliminated.
At this time, it is suspected that there is a problem with the program. It is caused by not adding the newly added sites after the technical transformation. Check the HRADWARES in the program, as shown in the following figure: The DP sites of the faulty machine are 3 less than the DP sites of the normal machine, so it can be judged as the program Version issue.
Result: After downloading and installing a copy of the recently backed-up program, the fault is eliminated. Later, I learned that the cause of the failure was the mistakenly downloading and using the program long ago as an in-use program when updating the industrial computer.
Figure: Hardware site of the faulty machine
Figure: Normal machine hardware site
When dealing with electrical and automation, they must be good at discovering the characteristics of different faults and be good at summarizing them. Also, it is very important to work carefully.
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