electric energy meter Select the contact's ratings

According to the controlled object and operating parameters such as voltage, current, power, frequency and operating system, such as determining the power transformers‍ contactor ratings.

1) contactor coil voltage, should generally be lower as well, so that contact can reduce the insulation requirements, while also safer to use. However, in order to facilitate and reduce the equipment electric energy meter‍, often by the actual grid voltage selection.

2) operation of the motor frequency is not high, such as compressors, pumps, fans, air conditioners, punch, etc., contact rated load current is greater than the rated current can be. Contactor type can be used CJl0, CJ20 and so on.

3) heavy duty motors, such as machine main motor, lifting equipment, winches, crushers, etc., the average operating frequency of more than 100 times / min, start running, jogging, forward and reverse brake, reverse braking, etc. state, the choice CJl0Z, CJl2 type of contactor. In order to ensure the electrical life, make contacts with derating. When selected, the contactor rated current greater than the motor rated current.

4) special heavy duty motor, such as printing presses, boring, etc., high operating frequency, up to 600 to 12,000 times / h, often running start, reverse brake, reverse and other state, mcb circuit breaker‍ according to the electrical contacts roughly life and starting current selection, model selection contactor CJl0Z, CJl2 so on.

5) AC circuit capacitors into the grid or the removal from the grid, the contactor closing capacitor selection should consider the impact of current. 1.5 In general, the contactor rated capacitor current can be rated current selection, model selection CJ10, CJ20 and so on.

6) When the transformer with contactor control, you should consider the size of the inrush current. AC arc welder for example, resistance welding machines, etc., generally can be 2 times the rated current of the transformer selected contact, model selection CJl0, CJ20 and so on.

7) For the electric equipment, such as a resistance furnace, electric heaters, etc., cold resistance load is small, so the starting current corresponding to a large number. May not consider (starting current) when selecting contacts, press the load rated current selection. Models can be used CJl0, CJ20, etc.

8) Because of the gas discharge lamp starting current, starting a long time, for the control of lighting equipment, according to the rated current of 1.1 to 1.4 times the selected AC contactor, models available CJl0, CJ20 and so on.

9) Contactor contactor rated current is under long-term maximum allowable current, duration ≤8h, and installed in the open control panel, if the cooling conditions are poor, the selection of contactors, the contactor rated by 110% to 120% of rated load current selection. For the motor to work long hours, due to the oxide film is no chance to get it cleared, the contact resistance increases, resulting in contact heat exceeds the allowable Air circuit breaker‍ temperature rise. When the actual selection, you can contact the rated current is reduced by 30% using.