Selection ① Press contactor control objects, the number of operations and the use of categories to select the appropriate category of contacts. ② line position by using the rated voltage selection. ③ Press the load capacity options contactor main contacts rated current. ④ For the attraction coil voltage level and current type of control power requirements should be considered. ⑤ capacity options for auxiliary contacts, according to the number of demand and the connected interlock circuit interrupter contacts current size considerations. ⑥ for making and breaking capacity issues contactor, the choice should pay attention to some use category loads such as capacitors, tungsten and other lighting devices, when connected to the current value of its large, on-off time is longer, the choice should be left margin. ⑦ For contactor electrical life and mechanical life issues, from the known average number of operations per hour and the life of the machine age, calculate the required electrical life, if it can not meet the requirements should be derated. ⑧ selection should consider the environmental temperature, humidity, vibration using the workplace, dust, chemical corrosion, etc., should be the appropriate environment to use different types of contacts. ⑨ device is suitable for lighting contactors, should also consider the type of lighting, the starting current size, duration and long-term work starting current, contact the current selection of electrical equipment should not exceed 90% (line) of the rated current. Capacitive compensation for tungsten and lighting equipment, should consider making current value. ⑩ design should be considered a secondary device operation consistency. Maintenance and inspection items ① run: 1) load current through is within the rating of the contactor; 2) the switching signal indicating contactor is consistent with the state of the circuit; whether 3) Run the sound normal, the presence or absence due to poor contact issued discharge sound; 4) whether the electromagnetic coil overheating, short-circuit ring electromagnet without exception. 5) interrupter cover loose and damage; 6) the presence or absence of auxiliary contacts burning case; 7) transmission parts without damage; 8) factors in the presence or absence of adverse operating environment is running, such as excessive vibration, poor ventilation , such as excessive dust. ② Maintenance: When electrical equipment for maintenance work, should be a contactor and maintenance work. 1) External maintenance: a. External cleaning dust; b. Check for loose fasteners, especially conductor connecting portion, to prevent contact loose and fever; 2) contact system maintenance: a. Check the dynamic and static contact position is positive, phase is closed simultaneously, any questions should be adjusted contact spring; b. Check contact wear, wear depth not exceeding 1mm, contacts have burning, welding off when opened, shall be replaced; when a slight burning, generally does not affect use. When allowed to use sandpaper to clean the contacts, you should use plastic filing; c. Measuring phase insulation resistance, resistance of not less than 10MΩ; d. Check auxiliary contact action is flexible, contact trip should meet the specified value, check whether the contacts fall off, found the problem, should be repaired or replaced. 3) The core part of the maintenance: a. Clean the dust, especially the moving parts and the contact surface between core pull; CJ20 AC contactor b. Check fastening core, the core running loose will cause the noise to increase; c. Core short ring has come off or broken should be promptly repaired. 4) solenoid maintenance: a. Measuring coil insulation resistance; b. Coil insulation discoloration, aging, coil surface temperature should not exceed 65 ° C; c. Check the coil wire connection, if open welding, burning should be promptly repaired. 5) Part interrupter cover maintenance: a. Check interrupter cover is damaged; b. Interrupter cover and position location without loose change; c. Remove metal particles and debris inside the arc chute gap.