What are the working principles and classifications of AC contactors?

Contactors are divided into AC contactors (voltage AC) and DC contactors (voltage DC), which are used for power, power distribution and electric field combination. In a broad sense, a contactor refers to an electrical appliance that uses the current flowing through the coil to generate a magnetic field to close the contact in order to control the load in industrial electricity.

The working principle of the contactor is that when the contactor coil is energized, the coil current will generate a magnetic field, which will make the static iron core generate electromagnetic attraction to attract the moving iron core, and drive the AC contactor point action. The normally closed contact is open, and the normally open contact is closed. The two are linked. When the coil is powered off, the electromagnetic attraction disappears, and the armature is released under the action of the release spring to restore the contact. The normally open contact is disconnected, and the normally closed contact is closed. The working principle of DC contactor is somewhat similar to that of temperature switch.

Main classification

It is divided into DC contactor and AC contactor according to the form of main contact connection circuit.

It is divided into electromagnetic contactor and permanent magnet contactor according to operating mechanism.

Permanent magnet AC contactor is a kind of micro power consumption contactor, which uses the same polarity of magnetic poles to repel each other and uses permanent magnet drive mechanism to replace the traditional electromagnet drive mechanism.

DC contactor

Development of DC Contactors at Home and Abroad

The overall development trend of contactors will be towards the direction of long electrical life, high reliability, multi-function, environmental protection, multi specification, intelligence and communication.

Hybrid DC contactor

Compared with AC current, DC current does not have periodic zero crossing of current value. Therefore, when traditional contactors break the circuit, the arc between contacts is relatively strong and the arcing time is relatively long, so as to fully release the remaining energy in the circuit. The burning of the arc produces high temperature and strong light, which has a serious ablation effect on the contact surface. The contact material gradually loses after several interruptions. When the contact is severely worn, the DC contactor will be scrapped and the circuit cannot be disconnected.

With the rapid development of power electronic technology, people apply power electronic components to DC contactors and ingeniously create a hybrid DC contactor, which makes DC contactors a new step towards intelligence and controllability. This hybrid contactor takes advantage of the advantages of small contact resistance and small conduction voltage drop of the traditional DC contactor in the closed conduction state, and parallels the contactless switch composed of anti parallel thyristors and control module units on the contact of the traditional DC contactor. This contactless power electronic switch does not produce electric arc when breaking the circuit, which avoids the electric wear of the electric arc to the contact material in the traditional contactor, and greatly increases the service life and reliability of the contact.

Permanent magnet mechanism of DC contactor

As one of the widely used electrical switches, the DC contactor has a huge number of production and demand. In the normal use process, the electromagnet coil has been working with electricity, generating electromagnetic attraction, ensuring the iron core and the armature are engaged, with moving and static contacts closed, and the circuit is connected. In the above process, the coil itself has resistance and continuously consumes electric energy, which is one of the main use costs of DC contactors and wastes a lot of energy and property. Therefore, how to reduce the working energy consumption of DC contactors is the key and difficult point to study DC contactors. The permanent magnet operating mechanism of DC contactor is a hybrid operating mechanism developed on the basis of the traditional electromagnetic operating mechanism of DC contactor, which combines the electromagnetic operating mechanism with the permanent magnet. It not only uses the original electromagnetic attraction and spring reaction force as the power to pull in and separate the iron core, but also adds the attraction of the permanent magnet to the iron core. Energy storage capacitors are used to charge and discharge to provide closing and opening power, It is usually called "electromagnetic operation, permanent magnet holding and electronic control". In the process of opening and closing, electromagnetic attraction, permanent magnetic attraction and spring force work together. In the process of stable operation, permanent magnetic attraction is used to replace the previous electromagnetic attraction to keep the armature and iron core in a closed state. First, the permanent magnet operating mechanism saves a lot of power consumption of the holding coil, which is environmentally friendly and energy-saving. On the other hand, compared with electromagnetic attraction, permanent magnet retention attraction has low noise and no pollution. Third, the permanent magnetic actuator eliminates a series of complicated and cumbersome locking protection devices in the electromagnetic mechanism, greatly improving the working reliability of the contactor operating mechanism, reducing the production process and cost, and reducing the volume of the contactor.