1. When choosing a contactor, we should start from the working environment, and mainly consider the following factors.
Control of AC load should be selectedAC contactorsDC contactor is selected for DC load.
The rated working current of the main contact should be greater than or equal to the current of the load circuit, and it should also be noted that the rated working current of the main contact of the contactor is the current value that can work normally under the specified conditions (rated working voltage, use category, operating frequency, etc.), and this current value will also change when the actual use conditions are different.
The rated operating voltage of the main contact should be greater than or equal to the voltage of the load circuit.
The rated voltage of the coil should be consistent with the voltage of the control loop.
2. Specific steps for contactor selection.
To select the type of contactor, you need to select the type of contactor according to the type of load.
Load type: Class I, Class II, Class III, Class IV.
Tag names: AC-1, AC-2, AC-3, AC-4
Control objects: non-inductive or inductive load, start and stop of asynchronous motor, operation and operation of cage asynchronous motor, start, reverse braking, reversal and jog of cage asynchronous motor, select the rated parameters of contactor.
According to the controlled object and working parameters, such as voltage, current, power, frequency, etc., determine the rated parameters of the contactor.
1) The coil voltage of the contactor should generally be lower, so that the insulation requirements of the contactor can be reduced, and it is safer to use. When the control circuit is simple and the electrical appliances are relatively small, the voltage of 380V or 220V can be directly selected. If the circuit is complex. If the number of electrical appliances used exceeds 5, a coil with a voltage of 36V or 110V can be used to ensure safety. However, in order to facilitate and reduce the equipment, it is often selected according to the actual grid voltage.
2) The operating frequency of the motor is not high, such as compressors, pumps, fans, air conditioners, etc., and the rated current of the contactor is greater than the rated current of the load.
3) For heavy-duty motor, such as the main motor of the machine tool, lifting equipment, etc., the rated current of the contactor is greater than the rated current of the motor when selected.
4) For special purpose motors. When it often runs in the state of starting reversal, the contactor can be selected according to the electric life and starting current, and CJ10Z, CJ12, etc
5) When using a contactor to control the transformer, the magnitude of the inrush current should be considered. For example, for electric welding machines, the contactor can generally be selected according to 2 times the rated current of the transformer, such as CJT1, CJ20, etc.
6) The rated current of the contactor refers to the maximum allowable current of the contactor under long-term work, the duration is 8h, and it is installed on the open control board, if the cooling conditions are poor, when the contactor is selected, the rated current of the contactor is 1 of the rated current of the load1-1.2x selection.
7) Select the number and type of contactors. The number and type of contacts should meet the requirements of the control circuit.
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Zhejiang Yishuo Electric Co., Ltd. is a high-tech company specializing in R&D, design, production, sales and service of low-voltage power capacitors, smart capacitors, reactors, reactive power compensation controllers, and reactive power compensation devices.
The company adheres to the tenet of "taking science and technology as the driving force and seeking development by quality", and is committed to building a leading brand of smart grid professional services. The company adheres to the tenet of "taking science and technology as the driving force and seeking development by quality", and is committed to building a leading brand of smart grid professional services.
The company has a high-level R&D management team, integrating R&D, production, sales and service, focusing on intelligent reactive power compensation, harmonic control, energy saving and power quality management and other high-tech industries of power automation.
Over the years, we have adhered to the mission of "making products intelligent and services intimate". In line with a high sense of responsibility to the society and users, Yishuo Electric adheres to the road of specialization, continues to innovate and transcend, and strives to make greater contributions to China's smart grid power automation