Parameters and Their Meanings of AC Contactors

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# Model Parameters

- **Model Naming Rules**: It usually consists of letters and numbers. Different manufacturers may have slight differences, but generally follow certain rules. Take the common CJX2-1210 as an example. "C" represents contactor, "J" represents alternating current, "X" represents low capacity or small size, "2" refers to the design serial number, "12" refers to the rated working current of the AC contactor, and "10" refers to the contact status of the AC contactor, that is, 1 set of normally open contacts (NO) and 0 set of normally closed contacts (NC). If it is 01, it means 0 set of normally open contacts (NO) and 1 set of normally closed contacts (NC).

### Electrical Parameters - **Rated Voltage (Ue)**: It refers to the rated working voltage of the main contacts, which should be greater than or equal to the rated voltage of the load. It is the voltage value at which the contactor can operate normally. Commonly used rated voltage values are 220V, 380V, 660V, etc., and the rated voltage applied in special occasions can be as high as 1140V.

- **Rated Current (Ie)**: It is the current value of the contactor contacts under the rated working conditions. It is a key parameter for measuring the load-carrying capacity of the contactor and determines the size of the load that the contactor can control. Commonly used rated current grades are 5A, 10A, 20A, 40A, 60A, 100A, 150A, 250A, 400A, 600A, etc.

- **Conventional Thermal Current (Ith)**: It refers to the current that the contactor is allowed to pass through under the specified working system in an 8-hour working system. This current is usually larger than the rated current of the contactor to ensure that the contactor will not overheat during normal operation, thus ensuring the life and safety of the contactor, that is, the maximum current that it can withstand at the limit.

- **Breaking and Making Capacity**: It can be divided into the maximum making current and the maximum breaking current. The maximum making current refers to the maximum current value that will not cause contact welding when the contacts are closed; the maximum breaking current refers to the maximum current that can reliably extinguish the arc when the contacts are opened. Generally, the breaking and making capacity is 5 to 10 times the rated current. Of course, this value is related to the voltage level of the opened circuit. The higher the voltage, the smaller the breaking and making capacity.

- **Rated Voltage of the Pull-in Coil**: It is the voltage value applied to the pull-in coil when the contactor is working normally. Generally, there are several types such as 36V, 110V, 220V, and 380V. This voltage value as well as data such as the number of turns and wire diameter of the coil are marked on the coil package instead of on the nameplate of the contactor housing. When selecting, it should be determined according to the power supply voltage of the control system to make them consistent.

- **Operating Values**: It can be divided into pick-up voltage and release voltage. The pick-up voltage refers to the minimum voltage at which the contactor can pick up when the voltage at both ends of the pull-in coil is slowly increased before the contactor picks up; the release voltage refers to the maximum voltage at which the contactor releases when the voltage at both ends of the pull-in coil is slowly decreased after the contactor picks up. Generally, it is stipulated that the pick-up 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.

Mechanical and Usage Parameters

- **Mechanical Life**: It refers to the number of operations (closing and opening) that the contactor can perform without damage under the condition of no electrical load. It is an important indicator for measuring the durability of the contactor and reflects the reliability and service life of the contactor.

- **Electrical Life**: It refers to the number of times that the contactor can reliably close and open under the specified voltage, current and usage category. It is also an important indicator for measuring the performance of the contactor and directly affects the service life and safety performance of the contactor.

- **Rated Operating Frequency**: It refers to the number of operations allowed per hour, generally 300 times/h, 600 times/h, 1200 times/h, etc. If the operating frequency is too high, it will cause the coil to overheat and affect the normal use of the contactor. Therefore, it is necessary to select an appropriate operating frequency according to the working frequency of the load equipment.