An improvement to ensure the stability of equipment start and stop signals

Since the author works in an old industrial and mining enterprise, the equipment is outdated and there are many control points. The photoelectric signals of each device start and stop are related to the safety of operators and equipment and the requirements of the process flow, and must be accurate. However, since the original circuit (see the figure below) uses the CJ12-400A AC contactor node frame contacts as the control nodes, due to busy production, the equipment start and stop frequency is high, and the contactor pulls in and releases to cause large vibrations, which often causes poor contact of the node frame contacts, resulting in the signal light being on and off, which brings serious hidden dangers to safe production.

A very simple and intuitive improvement was made to this circuit. Only a CJT1-10A (380V, 11VA) small AC contactor was installed next to the CJ12-400 AC contactor (about 400mm away, depending on the actual position), and its coil was directly connected with the coil of the CJ12-400 AC contactor, and the main contact of the small contactor directly replaced the node frame contact of the CJ12-400 AC contactor. After the improvement, due to the small size and small vibration of the small contactor, it can be opened and stopped at the same time as the large contactor, effectively avoiding the signal instability caused by the large vibration. The improvement has been used for 5 years and the effect is good. This improvement is also of certain significance to the life extension of some large and medium-sized old CJ12 contactors. It overcomes the disadvantage of having to replace the entire contactor due to the difficulty of matching the node frame, and truly plays the role of making the best use of everything.