With the development of technology in the field of electricity, there is an increasing need for control and management thereof. For this, special targeted devices are needed. The most popular devices were electromagnetic contactors. Some of them are used to bind individual elements of different patterns.
Machine description
The term "contactors" refers to remote control devices that perform the functions of closing and opening power lines in stable operating conditions. These devices have received widespread use and are the main connecting nodes in the circuits of an automated electric drive.
Previously, such contactors were used to control and monitor the engines of railway electric locomotives and other similar units. Nowadays, they are often used in electronics and everyday household electrical operation.
Depending on the type of drive switching system, there are electromagnetic, pneumatic and hydraulic contactors. The basis of contact and arcing systems, the kinematics of mechanisms and other details are similar in their principal action in these devices.
According to the periodic frequency of line closure and opening in a certain period of time, contactors are divided into classes marked with 0.3, 1.3, 10, 30. These indicators correspond to the frequency of 30, 120, 1200 and 3600 closures / openings for 60 minutes.
Device classification
These electromagnetic contactors in their classification are divided into:
- by type of electricity in the main circuit and control line - direct current, alternating current or direct and alternating current together;
- by the number of main poles (from 1 to 5);
- according to the rated current of the main line (from 1.5 to 4800 A);
- according to the calculated voltage of the main line (from 27 to 2000 V DC, from 110 to 1600 V AC and with a frequency of 50 to 10000 Hz);
- according to the calculated voltage of the electric coil including (from 12 V to 440 in an alternating current network, from 12 to 660 V in an alternating current line at a frequency of 50 Hz and in an alternating voltage network from 24 to 660 V with a 60 Hz frequency);
- by the presence of secondary contacts (with or without contacts).
Electromagnetic contactors-starters are also divided by the type of switching of the conductors of the main line and the control line, by the installation methods, by the methods of connecting third-party conductors, and so on.
These parameters are assigned only to those devices that were manufactured at an industrial enterprise.
Contactor Operation
The stable operability of the device is determined at a voltage at the junction of the main line up to 1.1 and a control line from 0.85 to 1.1 of the calculated voltage of these circuits. The tolerance is also open for the normal operation of the contactor when the AC voltage drops to 0.7 from the calculated one, while the task of the coil is to hold the armature of the electric magnet in the closest position and during the voltage drop it should not delay it.
Modifications of electromagnetic contactors made in the industrial field are intended for operation in various climatic zones, under various influences, which are determined by the location at work, mechanical processes and negative environmental influences. Devices in their general design features do not have special protection against external influences.
The function of closing the contactors occurs during the supply of current to the winding of the electromagnetic drive. The anchor node of this element moves to the core and in parallel with this, the movable contact approaches a fixed contact. There is a switching power circuit.
The main thing in the circuit of connecting electromagnetic contactors is to observe the correct sequence. Be sure to strictly follow the safety rules in working with electrical appliances. Do not manipulate live parts.
Opening is characterized by a drop in voltage from the coil. Disconnection of the closed contacts occurs due to the action of the gravity of the moving units and the straightening of the return spring.
Device design
The electromagnetic contactor includes such main functioning elements as the main contacts, the arcing and electromagnetic systems, and secondary assisting contacts.
The main contacts perform the task of closing / opening the power line. Their operational capabilities are designed for a long time under voltage, a huge number of operating moments on / off with the highest execution frequency.
The normal state of the contacts is determined when the retracting coil is not energized, and all mechanical latches are in free form. The main contacts can be lever or bridge type. The lever-type contacts have a moving system with rotary capabilities, and the bridge ones have a linear one.
Arc Extinction System
The arcing structure extinguishes directly the electric arc, which appears when the main contacts are turned off. Its methods and schemes for connecting electromagnetic contactors together with the design of the arcing principle are determined by the type of current of the main circuit and the operating conditions of the contactor itself.
The arcing compartments of these DC devices are designed on the principle of suppressing an electric arc by means of a magnetic field in compartments with longitudinal slots. A magnetic field, in the main number of models, is excited by an interrupter coil alternately connected with the contacts.
Contactor selection
The MK series of electromagnetic contactors is used in vehicles tied to rail movement, in trolley buses and in large industrial stationary devices. These devices operate in circuits with direct current and alternating current. Some models are used in elevator low-voltage integrated control units.
The selection of these electrical appliances must follow such technical requirements as:
- scope and purpose of operation;
- application category;
- stability in terms of mechanics and switching;
- the number of contact groups in electromagnetic contactors;
- type of current and power of the rated voltage, including the main circuit;
- rated voltage and required power of coils;
- climatic conditions and operating procedures.
The cost of appliances
Contactors in the market of electrical goods are sold at various prices. It depends on technical characteristics, on models and modifications, conditions and modes of use and the manufacturer's company. For example, the price of an electromagnetic contactor for an alternating current of 4 kW varies around 1000 rubles, and the contactor of the KT-6023 model will already cost about 6300 rubles.