The AC Contactor (Alternating Current Contactor), as a whole, Continuous improvement in shape and performance, But with the same functionality, Mainly composed of electromagnetic system, contact system, arc extinguishing device and auxiliary components, The electromagnetic system is mainly composed of coil, iron core (static iron core) and armature (moving iron core) three parts; Contact system is divided into point contact, line contact and surface contact three; The arc extinguishing device often adopts the double fracture electric arc extinguishing, longitudinal joint arc extinguishing and gate arc extinguishing three arc extinguishing methods, To eliminate the electric arc generated by the dynamic and static contacts during the division and closing process, Contactors with a capacity above 10A have arc extinguishing devices; Auxiliary components mainly include reaction spring, buffer spring, contact pressure spring, transmission mechanism, base and terminal column and so on.
The working principle of the AC contactor is that when the contactor coil is energized, the coil current will produce a magnetic field, and the generated magnetic field makes the static core produce electromagnetic suction to attract the core, and drive the AC contact point action, often closed contact disconnected, often open contact closed, the two are linkage.When the coil is powered off, the electromagnetic suction disappears, and the armature is released under the action of the release spring to make the contact recover, the often open contact breaks, and the often closed contact closes.It is to use electromagnetic force and spring elasticity to cooperate, to achieve the contact connection and separation.
According to the customer requirements, the manufacturing of control cabinets for customers, no matter in the choice of communication contactors or other components, they will try their best for customers to select and meet the requirements of high-quality domestic and foreign components.
Selection principle of AC contactor:
(1) The voltage level should be the same as the load, and the type of contactor should be suitable to the load.
(2) The calculated current of the load shall conform to the capacity level of the contactor, that is, the calculated current is less than or equal to the rated working current of the contactor.The connecting current of the contactor is greater than the starting current of the load, and the breaking current is greater than the operation of the load. The calculated current of the load should consider the actual working environment. For the load with a long starting time, the peak current of half an hour can not exceed the agreed heating current.
(3) Check the short-time dynamic and thermal stability.The three-phase short circuit current of the line shall not exceed the allowable dynamic and thermal stable current of the contactor. When the short circuit current is disconnected by the contactor, the breaking capacity of the contactor shall also be verified.
(4) The rated voltage, current, the quantity and current capacity of the auxiliary contacts of the suction coil of the contactor shall meet the wiring requirements of the control circuit.To consider the line length connected to the contactor control loop, the general recommended operating voltage value, the contactor needs to work at 85~110% of the rated voltage value.If the line is too long, the contactor coil may not reflect the closing instruction due to the high voltage drop; the trip instruction may not work with the high line capacitor.
(5) Check the allowable operation frequency of the contactor according to the operation times.If the operating frequency exceeds the specified value, the rated current should be doubled.
(6) The short-circuit protection element parameters should be selected together with the contactor parameters.Please refer to the sample manual, which generally gives the matching table of contactors and fuses.
Post time: Jun-10-2022
