Contactors are widely used in industrial production and are of great significance for the safety of equipment and personnel.
Working principle of the contactor
When the contactor coil is energized, the current in the coil generates a magnetic field, which causes the static iron core to generate electromagnetic attraction to attract the moving iron core and drive the AC contactor to act. The normally closed contact disconnects, while the normally open contact closes. They are linked. When the coil is de-energized, the electromagnetic attraction disappears, and the armature is released under the action of the release spring, causing the contacts to return to their original state.
Components of the contactor
1.Contact part :This is the core part of the contactor and has the functions of energizing and de-energizing. It is usually composed of fixed contacts and moving contacts. The main contacts are used to connect and disconnect the main circuit, while the auxiliary contacts are used to control other parts of the circuit.
2. Electromagnetic Mechanism: The electromagnetic mechanism consists of coils, moving armature (contactor) and stationary armature. Its function is to convert electromagnetic energy into mechanical energy, generating electromagnetic attraction to drive the contacts to move. When the electromagnetic coil is energized, the moving armature will be attracted by the electromagnetic force and will either directly or through lever transmission make the moving contacts contact the stationary contacts, thus connecting the circuit. When the electromagnetic coil is de-energized, the moving armature will automatically return under the action of the reset spring, and the contacts will open, thus disconnecting the circuit.
3. The insulating part :It is mainly composed of insulating materials. It is used to separate the electrical part from the mechanical part, preventing current from leaking out or causing electric shock hazards.
4. The mechanical components :It are used to connect and fix the contacts and the insulating parts. They also include mechanical components such as the switch handle and spring, which are used to control the working state of the contact.
Contactor selection
When selecting a contactor, the following parameters need to be determined:
1. Type of contactor: Is the main circuit AC or DC?
2. Main circuit voltage: The rated voltage of the main circuit. It can be referred to as the rated voltage of the contactor.
3. Voltage and power consumption of the control coil: Besides the rated voltage, another important parameter of the contactor is the coil voltage. As the name suggests, the coil voltage is the voltage applied across the terminals of the contactor's coil. The working principle of the contactor is as follows: When the coil of the contactor is energized, the main contacts of the contactor engage, and at this point, the main circuit is connected, allowing the motor to operate; when the coil of the contactor is de-energized, the main contacts of the contactor disengage, and the motor stops.
4. Number and capacity of auxiliary contacts: Generally, based on the requirements for the number and capacity of auxiliary contacts in the application, appropriate contactors for auxiliary contacts can be selected or installed.
5. Whether it is for special industry applications: such as railway-specific, wide coil voltage, etc. In such cases, the corresponding special application contactors should be selected.
6. Whether it is for special application scenarios: For example, in altitude applications, capacity reduction is required. The contactor's altitude reduction parameters can be selected accordingly.
7. Are additional accessories required? Such as surge suppressors and mechanical interlock devices.
8. Whether specific product certifications are required: such as CCC, UL certification, etc.
Applications of contactors
In industrial control systems, contactors are one of the most common components. They are widely used in the control systems of large machines and equipment, controlling the operation of electric motors, lighting, and other devices through switching circuits. Contactors can also be used to control pneumatic and hydraulic systems, as well as the automation control systems of various factory equipment. For example, in places like trams, subway stations, and train stations, automatic doors and barrier doors on sidewalks are controlled by contactors to open and close. Additionally, contactors can be used to control car lights, electric windows, and air conditioning systems in ordinary cars. Especially in large commercial and residential buildings, contactors can control the switches, adjustments, and coordination of lighting and air conditioning systems through switching circuits, achieving energy conservation and intelligent control. Agriculture: In the agricultural field, contactors can be used to control irrigation systems, feed processing equipment, and livestock and poultry breeding facilities. They can automatically start and stop equipment as needed and provide protection functions.
in summary
A contactor is an automatic switch that uses electromagnetic principles to control the on-off of a large current circuit with a small current. Its main function is to achieve remote control and automation, and it also has the ability to operate frequently and basic overvoltage and undervoltage protection functions. It is one of the most fundamental and core control electrical appliances in modern industrial automation.
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Shaanxi West Power Tongzhong Electrical Co., Ltd.
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