Troubleshooting a contactor failure

As an electrician, there are countless problems to be dealt with every day. Some problems can be quickly solved with reference to the component manuals, while some problems require clear thinking and patience to check step by step.
Recently, a particularly strange thing was discovered during device debugging. This is a transformation of the old equipment that has been in production for six or seven years. One of the conveyor belt motors is still running after the equipment stops running. The same is true for switching the manual automatic mode to the manual mode. When I saw this, I immediately took an emergency stop, but it was surprising that the emergency stop did not respond. If the emergency stop device is still running when an accident occurs, the consequences are unimaginable, so I immediately started looking for the reason.
Troubleshooting a contactor failure

First of all, I checked from the program that is the easiest to change, and the program error is the most likely. However, whether switching to manual or taking an emergency stop, the signals that control the conveyor start in the program are reset. Then the possibility of a program error is ruled out.
Then I thought, since the conveyor belt is running, it must be where the start signal is given. Because it is an old device, will someone change its startup signal before, causing its output point in the program to change. So I cut off the total power of the device and began to check the line step by step along the start signal. However, it was found that the start signal did not change, and because the equipment environment was harsh, the cable trough cover was dusty. At that time, there was an impulse to give up. So since there is no problem in front, the last reason may be on the contactor. Initially my idea was that the contacts might have glued together and could not be disengaged. When the corresponding contactor is found, the coil is still "sucked", but the total feel is a bit wrong, and the coil button looks a little tilted. I gently dialed it with an electric pen, and the coil of the squeak was released. It turns out that the coil button is stuck, causing the coil to not be loosened, so there is always an alternating current output to the motor. The problem was finally found out.
Our current use of components such as contactors is still in the "open loop control" of the control concept, without any data feedback. If one day can be configured like the IO-l ink, it is configured into the entire automation system, and there is periodic data exchange with the controller, so that the running status of the components can be monitored in real time, and the unexpected failure of the device can be reduced. Unplanned downtime for intelligent control.
As an electrical person, you must continue to learn, have an attitude of not arrogant, and gain experience to be better qualified for the job.

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