In the electrical control system, the contactor is a crucial electrical component, which can frequently switch on and off the main AC-DC circuit and the large capacity control circuit.Understanding the classification and principle of contactors is the key to understanding the operation mechanism of electrical systems for electrical engineers, technicians and related enthusiasts.
Classified by the form of the main contact connection loop
1.Ac contactor: mainly used to connect and disconnect AC circuit.Its working principle is based on the law of electromagnetic induction.When the coil is energized, a magnetic field will be generated, so that the static core generates electromagnetic suction to attract the moving core, and drives the main contact to close and close the circuit.The core of the AC contactor is generally made of silicon steel sheet laminated to reduce the eddy current and hysteresis loss caused by the alternating magnetic field in the core.At the same time, the number of turns of the coil of the AC contactor is less, the resistance is smaller, and the inductive reactance is larger when the AC is passed, thus limiting the size of the current.
2.Dc contactor: used to make and break the direct current circuit.The working principle of the DC contactor is similar to that of the AC contactor, but because there is no alternating magnetic field in the DC circuit, its core is usually made of whole steel or engineering pure iron.In addition, the coil turns of the DC contactor are more and the resistance is larger to adapt to the characteristics of the direct current circuit.When the DC contactor breaks the direct current circuit, because the current can not be sudden, it will produce a high arc between the contacts, so special arc extinguishing measures need to be taken, such as magnetic blow out arc.
Classified by operating mechanism
1.Electromagnetic contactors: This is the most common type of contactor, which uses an electromagnetic force to drive the closing and breaking of contacts.The AC contactors and DC contactors mentioned above are mostly electromagnetic contactors.The electromagnetic mechanism is composed of iron core, coil and armature, and uses electromagnetic force to realize the action of contact, which has the advantages of simple structure and convenient operation.
2.Pneumatic contactor: Use compressed air as a power source to drive the action of the contact.This kind of contactor is usually used in harsh environment and high explosion-proof performance, such as coal mine.It pushes the piston or diaphragm through compressed air, which in turn drives the contact to close and break.Pneumatic contactor has the advantages of reliable operation and good explosion-proof performance, but it needs to be equipped with air source device, and the system is relatively complex.
3.Hydraulic contactor: hydraulic oil as a power transmission medium.It drives the piston or hydraulic cylinder through the pressure change in the hydraulic system to achieve the action of the contact.The hydraulic contactor has a larger operating force and is suitable for some occasions that require larger contact pressure, such as high-voltage and large-capacity power systems.However, the maintenance requirements of hydraulic contactors are high, and attention needs to be paid to the cleaning and sealing of hydraulic oil.
Classified by extinguishing medium
1.Air contactor: The use of air as the arc extinguishing medium.When the contact is broken, the arc cools and diffuses rapidly in the air, thus achieving arc extinguishing.The air contactor has simple structure and low cost, and is widely used in general electrical control occasions.
2.Oil-immersed contactor: The contact is immersed in insulating oil, and the cooling and arc-extinguishing effect of the oil is used to extinguish the arc.Oil-immersed contactors have strong arc extinguishing ability, but they are rarely used now because of oil leakage and complicated maintenance.
3.Vacuum contactor: the contact is closed and disconnected in the vacuum, because there is no gas in the vacuum, the arc is difficult to produce and maintain, so the vacuum contactor has the advantages of fast arc extinguishing speed, long life, small size and so on.It is often used in occasions with high electrical performance requirements, such as high-voltage switchgear and frequent operation of motor control.
Classified by the number of poles of the main contact
1.Single-pole contactor: only a pair of main contacts, mainly used in single-phase circuits, such as controlling the start and stop of single-phase motors.
2.Bipolar contactors: There are two pairs of main contacts, which can be used to control two-phase circuits or in some special control loops.
3.Three-pole contactor: the most common, there are three pairs of main contacts, widely used in three-phase AC circuits, used to control three-phase motors and other equipment.
4.Multi-pole contactor: The number of main contacts is four or more poles, usually used in some special electrical systems, such as the need to control multiple circuits at the same time.
Understanding the classification and classification principle of contactors helps us to correctly select and use appropriate contactors in different electrical application scenarios to ensure the safe and reliable operation of electrical systems. Whether in industrial automation production lines, or in the control of electrical equipment in daily life, contactors play an indispensable role.
Post time: Jan-06-2025