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Contactors are divided into AC contactors (voltage AC) and DC contactors (voltage DC), which are used for power, distribution and electric field connection. Contactor is a kind of electric appliance that uses coil to flow through current to produce magnetic field and make contact closed in order to control load like PG circuit breaker.

The working principle of the contactor is: when the contactor coil is powered on, the coil current will generate a magnetic field, the generated magnetic field will make the static iron core generate electromagnetic attraction to attract the moving iron core, and drive the action of the AC contactor point, the normally closed contact will open, the normally open contact will close, and the two are linked. When the coil is de energized, the electromagnetic attraction disappears, and the armature is released under the action of the release spring, so that the contact is restored, the normally open contact is opened, and the normally closed contact is closed.

In Electrotechnics, because it can cut off the AC and DC main circuit quickly and turn on and off the large current control (up to 800A) circuit frequently, it is often used in the motor as the control object, and it can also be used to control the power load such as plant equipment, electric heater, working mother machine and various power units. The contactor can not only turn on and cut off the circuit, but also has low power Pressure release protection. PG circuit breaker is also one of the important components in automatic control system, which has large control capacity and is suitable for frequent operation and remote control. In industrial electric, there are many types of contactors, with working current varying from 5A to 1000A, which are widely used. AC and DC contactors exist in many industrial motors, including the automotive industry. Different contactors perform the same task, but they do it in different ways.


According to electrotechnik.net, DC relays use flywheel diodes to release electromagnetic forces accumulated in the inductance when the coil is de energized. The AC contactor does not adopt the structure of free wheel diode, but adopts laminated magnetic core to prevent the loss of heat and shadow coil, so as to make the electric energy run efficiently in the equipment.


Due to the shading coil of AC, the device can be placed in any position as long as it has operation space. The DC contactor needs air when it works, so there must be enough clearance around the equipment to work normally.


Although AC contactors are considered a more reliable and cheaper product, DC contactors are designed to allow custom speeds and torques. This is ideal for projects that do not follow existing templates, such as building robot arms from scratch.


Installation Guidelines
IEC 61439
International standards


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