Basic Parameters Of AC Contactors

(1) Rated voltage: refers to the rated working voltage of the main contact, which should be equal to the rated voltage of the load.

(2) Rated current: The current value of the contactor contact under rated working conditions. In the control circuit of a 380V three-phase motor, the rated working current can be approximately twice the control power. The commonly used rated current levels are 5A, 10A, 20A, 40A, 60A, 100A, 150A, 250A, 400A, and 600A.

(3) Making and breaking capacity: can be divided into maximum making current and maximum breaking current. The maximum making current refers to the maximum current value that does not cause contact fusion welding when the contact is closed; The maximum breaking current refers to the maximum current that can reliably extinguish the arc when the contact is disconnected. The general breaking capacity is 5-10 times the rated current. Of course, this value is related to the voltage level of the breaking circuit, as the higher the voltage, the smaller the breaking capacity.

(4) Action value: can be divided into pull-in voltage and release voltage. The pull-in voltage refers to the minimum voltage that a contactor can pull in by slowly increasing the voltage at both ends of the pull-in coil before the contactor pulls in. Release voltage refers to the maximum voltage at which the contactor releases when the voltage of the closing coil is slowly reduced after the contactor is closed. As a general rule, the pull-in voltage shall not be lower than 85% of the rated voltage of the coil, and the release voltage shall not be higher than 70% of the rated voltage of the coil

(5) Rated voltage of the suction coil: The voltage applied to the suction coil when the contactor is operating normally.

(6) Operating frequency: At the moment of contactor closing, the suction coil needs to consume 5-7 times more current than the rated current. If the operating frequency is too high, it will cause serious heating of the coil, directly affecting the normal use of the contactor. Therefore, it is necessary to limit the operating power.

(7) Life: including electrical life and mechanical life. At present, the mechanical life of contactors has reached over 10 million times, and the electrical life is about 5% to 20% of the mechanical life.