When selecting an AC contactor according to the load, it is often only selected according to the rated current of the load, so that the main contact of the AC contactor often burns out and fuses in actual operation. The reason for this fault is that the method of selecting the AC contactor (main contact capacity) according to the rated current is only suitable for purely resistive loads such as heating wires.
For inductive loads such as three-phase asynchronous motors, the starting current is about 4-7 times the rated current due to different starting methods, drag load types, and starting frequencies. Before stable operation during startup. When choosing an AC contactor for this purpose, it is also very important and necessary to consider the factor of the load starting current.
With the enhancement of safe electricity awareness and safe operation standards, in order to reduce unnecessary electric shock accidents, the current AC contactor coil voltage-safe voltage level (AC36V) has become the general trend. Therefore, in the process of designing, selecting and assembling contactors, products with a coil voltage level of AC36V should be used first. Try to avoid the coexistence of coil voltage levels such as AC380V and AC220V in the line.
In order to reduce the number of other auxiliary devices (such as intermediate relays, etc.). ) and reduce the volume of the electronic control system. When selecting an AC contactor, the type of AC contactor should be comprehensively considered according to the number of auxiliary contacts required by the contactor in the line. For example, when there are many auxiliary contacts of the AC contactor in the line, it is more wise to choose the CJX series AC contactor that can hang 2 pairs or 4 auxiliary contacts than the CJT series AC contactor.
Combining the above three factors, what does not need to be compensated is the control method of the contactor (coil). At present, industrial control equipment such as PLC, which is convenient for centralized control, is more and more widely used. During this process, the contactor coil is directly connected to the PLC output, and the PLC internal output devices (relays, transistors, thyristors) are damaged. The cause of the failure is nothing more than that the current value of the contactor coil during the pulling process is greater than the current carrying capacity of the PLC output device. Therefore, when controlling the contactor with the programmable controller, the relay should be used as the control transition between them.
If there is anything else you need to know about AC contactors, you can contact us. We are a manufacturer of AC contactors, and we have a more detailed understanding of the characteristics and use of AC contactors. We can introduce the knowledge of AC contactors from different aspects.
