Contactor knowledge that the hottest newcomers mus

2022-08-02
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Newcomers must know the knowledge of contactors

low voltage electrical components are used for a long time, especially in dusty, high humidity and corrosive gas workplaces. The second state is easier: first, check whether the force measuring piston can be installed accurately and whether the friction force is too large. After clearing this reason, the push plate will be flustered and stuffy to the people on the outside, and the small plate will pass the adjustment. For example, the large and medium plates are still out of tolerance, The weight of B thallium and C thallium shall be properly reduced until the test is passed. At this time, our electricians are required to remove the fault timely and effectively to ensure the normal operation of the equipment. What I share in this article is some information about contactors summarized by myself. I hope it will be helpful and reference for you in your future work

common faults and causes of contactors

1. Contact fusion welding

one or three-phase contacts of AC contactors cause contact fusion welding fault due to large overload current (i.e. the dynamic and static contacts are ablated and stuck together and cannot be separated). At this time, after pressing the stop button in time, the motor will not stop running, and the "buzzing" sound may occur during operation. At this time, we should immediately disconnect the upper level air switch, and then conduct power outage maintenance

2. Contact phase loss

the fault is caused by poor contact of a phase contact or loose connecting bolts. At this time, the motor will make a dull "buzzing" sound. At this time, we will immediately cut off the power for maintenance, otherwise the motor may be burned due to long-term phase failure operation

3. Phase to phase short circuit

due to out of control interlocking or misoperation in the contactor control line, two or more contactors that should not be pulled in at the same time are put into operation at the same time (such as forward and reverse lines), resulting in phase to phase short circuit fault. For this reason, we can adopt multiple interlocking methods for prevention. For example, in the forward and reverse lines, we can adopt the double interlocking method of button plus auxiliary contact for control to ensure the further safety of the lines

in order to reduce the occurrence of the above faults, our electricians should regularly maintain the contactor. The general methods are as follows:

a. regularly check the working conditions of all parts of the contactor. The movable parts should be flexible without jamming, all fasteners should be free of looseness, and all internal spring accessories should be free of rust. If relevant parts are damaged, they should be repaired and replaced immediately

b. the contact surface of the contactor shall be regularly dusted to keep it clean. If particles are formed on the contact surface due to arc burning, the raw and auxiliary materials shall be regularly tested with a knife, and the supplier shall be assessed and evaluated (sandpaper and file are not allowed to be used for grinding); The contact shall be replaced when the ablation thickness exceeds 20 and the displacement rate control range (mm/min) is 0.5 (5) 0, which exceeds the original 2/3

c. the contact surface of the dynamic and static magnets of the contactor shall be kept clean. If there is dirt or oil stain on the contact surface of the iron core magnetic pole, it shall be cleaned to prevent large noise and vibration when the magnet is engaged, which will affect the normal operation of the contactor

d. the original AC contactor equipped with arc suppression cover must not remove the arc suppression cover and not use it, because it is the main facility to prevent interphase arc short circuit fault when the contactor disconnects the load

e. during the daily inspection of the contactor suction coil, pay attention to whether there is any discoloration or burning trace on its appearance and whether there is a burnt smell. If there are these phenomena, it indicates that the suction coil has been overheated and should be replaced immediately

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