The rated parameters of the contactor are mainly determined according to the voltage, current, power, frequency and working system of the charged equipment.
(1) The coil voltage of the contactor is generally selected according to the rated voltage of the control line. Considering the safety of the control line, it is usually selected according to the low voltage, which can simplify the line and facilitate the wiring.
(2) The selection of the rated current of the AC contactor should be considered by the load type, use environment and continuous working time. The rated current of the contactor refers to the maximum allowable current of the contactor under long-term operation, with a duration of 8 h, and is installed on the open control board. If the cooling condition is poor, the rated current of the contactor is selected by 110%~120% of the rated current of the load. For long-working motors, because the oxide film on the surface of the contact has no chance to be cleared, the contact resistance increases, and the contact heat exceeds the allowable temperature rise. In the actual selection, the rated current of the contactor can be reduced by 30%.
(3) Load operation frequency and working condition have a great impact on the selection of AC contactor capacity. When the operating capacity of the load exceeds the rated operating frequency, the contact capacity of the contactor shall be appropriately increased. For frequently starting and disconnected loads, the contact capacity of the contactor should be increased accordingly to reduce the contact corrosion and extend the service life.
2. Common fault analysis and maintenance of low-voltage AC contactor
AC contactors can break frequently during work and can wear the contactor contacts during use. At the same time, sometimes improper use, or use in a relatively harsh environment, will also shorten the life of the contactor, causing failure, therefore, in the use, but also to choose according to the actual situation, and in the use should be maintained in time, to avoid greater losses after the failure. In general, the common faults of AC contactors are contact faults, coil faults and other electromagnetic mechanical faults.
Post time: Nov-28-2022
