What is an AC Vacuum Contactor?

The alternating current vacuum contactor (AC vacuum contactor) is a kind of on-off switch used in an AC power supply environment, which is widely used in various control circuits at present.

AC Vacuum Contactor Structure Description

AC vacuum contactors use the main contact to open and close the circuit, with auxiliary contacts to conduct the control circuit. The main contact is generally normally open contact, while the auxiliary contact often has two pairs of normally open contacts and normally closed contacts, small contactors are often used as intermediate relays with the main circuit. AC contactor contacts, made of silver tungsten alloy, with good electrical conductivity and high-temperature ablation resistance. 

AC vacuum contactor action power from the AC through the magnetic field generated by the coil with an iron core, electromagnetic core by two young silicon steel laminated, one of the fixed core, set with a coil, the working voltage can be a variety of options. To make the magnetic force stable, the suction side of the core plus the short circuit ring. The AC vacuum contactor relies on the spring to reset after the loss of power. The other half is a movable core, the same structure, and fixed core used to drive the main contact and auxiliary contact closure and disconnection. 20 amps or more contactor plus an arc extinguisher, the use of electromagnetic force generated when the circuit is broken, quickly pull off the arc to protect the contact. High-capacity contactors can be operated at high frequencies, up to 1200 times per hour for power on and off control.

AC vacuum contactors are mainly composed of electromagnetic systems, contact systems, arc extinguishing systems and other parts.

1. Electromagnetic system: electromagnetic system includes an electromagnetic coil and iron core, which is an important part of the vacuum contactor, relying on it to drive the closing and breaking of contacts.

2. Contact system: contact is the executive part of the vacuum contactor, including main contact and auxiliary contact. The role of the main contact is to connect and break the main circuit and control the larger current, while the auxiliary contact is in the control circuit to meet the requirements of various control modes.

3. Arc extinguishing system: arc extinguishing device is used to ensure that when the contact is disconnected from the circuit, the resulting arc is reliably extinguished, reducing the arc damage to the contact. To quickly extinguish the arc when disconnected, usually vacuum contactors are equipped with an arc extinguishing device, generally using a half-sealed longitudinal seam ceramic arc extinguishing cover, and equipped with a strong magnetic arc blowing a circuit.

4. Other parts: insulated shell, spring, short circuit ring, transmission mechanism, etc.

AC vacuum contactor working principle

AC vacuum contactors use a primary contact to open and close a circuit and an auxiliary contact to execute control commands. The main contactor generally has only normally open contacts, while the auxiliary contactor often has two pairs of contacts with normally open and normally closed functions, and small contactors are often used as intermediate relays with the main circuit.

When the AC vacuum contactor solenoid coil is not energized, the reaction force of the spring and the self-weight of the armature core keep the main contact open. When the solenoid coil is connected to the control voltage through the control circuit (generally rated voltage), the electromagnetic force overcomes the reaction force of the spring and draws the armature to the static core, driving the main contact to close and turn on the circuit, and the auxiliary contact then acts.

Application of AC vacuum contactor

In electrical engineering, the contactor not only can turn on and off the circuit but also has the function of low voltage release protection. Contactor control capacity is large, suitable for frequent operation and long-distance control. It is one of the important components of the automatic control system.

In industrial electricity, there are many models of AC vacuum contactors, ranging from 5A-1000A, widely used in coal, metallurgy, petroleum, chemical industry, electric power, machinery, transportation, ships, construction, and other sectors.

Advantages of AC vacuum contactor

AC vacuum contactor has strong extinguishing ability, good voltage resistance, high operating frequency, long life, no arcing, small size, lightweight, and long maintenance cycle. The vacuum contactor vacuum interrupter manufacturing process is very demanding, if the process is not good, the vacuum of the interrupter is easy to decline. Contact material is not good, in the breaking current will appear "cut-off overvoltage" phenomenon, that is, in the breaking current, due to the vacuum interrupter arc extinguishing ability being very strong, the arc current is not natural over zero when cut off, but from a certain value of the current suddenly drop to zero, resulting in a high overvoltage. The interrupting voltage can endanger the safe operation of electrical equipment.

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