How to choose a suitable AC contactor

Selection
Selection of AC contactor, the type of load and the reasonable selection of working parameters. Concrete into the following steps:
1 type of contactor
AC contactor is divided into one class, two class, three class and four class according to the load type, denoted as AC4, AC3, AC2 and AC1 respectively. The control object of a type of AC contactor is non sense or micro load, such as incandescent lamp, electric resistance furnace, etc. the two type of AC contactor is used for starting and stopping of winding induction motor. The typical application of three kinds of AC contactor is the operation and operation of squirrel cage induction motor.
2 selection of the rated parameters of the contactor
According to the controlled object and working parameters such as voltage, current, power, frequency and working system, etc..
1) the coil voltage of the contactor, generally should be lower for good, so that the insulation requirements can be reduced, the use of the more safe. But in order to facilitate and reduce the equipment, often according to the actual power grid voltage.
2) motor operating frequency is not high, such as compressor, water pump, fan, air conditioning, punch, etc., contactor rated current is greater than the rated current. Contactor type can choose CJ20, CJl0, etc..
3) of the heavy task type motor, such as machine main motor, lifting equipment, winches, crushing machine, such as. The average operation frequencies more than 100 times / min, running to the starting point, is the reverse brake, reverse connect brake state, can choose CJl0Z, CJl2 type contactor. In order to ensure the electric life, the contactor can be used for reducing the capacity. Selection, the contactor rated current greater than the motor rated current.
4) of severe motor tasks, such as printing machine, boring machine etc., the operating frequency is very high, up to 600 ~ 12000 times / h, often running for starting, reverse connect braking, reverse state, contactor roughly can be according to the electrical life and starting current selection, the contactor type selection and CJl2 CJl0Z etc..
5) in an AC circuit of capacitor input from the power grid or removed from the grid and selecting contactors switching surge current of capacitor should be considered. Generally, the rated current of the contactor can be selected according to the rated current of the capacitor 1.5 times, the model selection of CJ10, CJ20, etc..
6) in the control of the transformer, the size of the surge current should be considered. For example, AC arc welding, resistance welding, etc., generally can be rated current of 2 times the rated current of the transformer, the selection of CJl0, CJ20, etc..
7) for the electric heating equipment, such as electric resistance furnace, electric heater, the load of the cold state resistance is small, so the starting current corresponding to a large number of. When the contactor is used, it is not to be considered (starting current), and the load current of the rated current is selected. Model can choose CJl0, CJ20, etc..
8) due to the gas discharge lamp starting current, starting time, for the control of lighting equipment, can be rated current 1.1 to 1.4 times the selection of AC contactor, model CJl0, CJ20, etc..
9) contactor’s rated current is refers to the contactor in long-term work under the maximum allowable current, the duration is less than or equal to 8 hours and is installed on the open control panel, if the poor cooling conditions, the choice of contactor, rated current of a contactor according to the load current rating of 110% ~ 120% selected. For a long time working motor, because the film has no chance to get rid of, so that the contact resistance increases, resulting in more than the allowable temperature rise of contact. In the actual use, the rated current of the contactor can be reduced by 30%.