With the development of technology in the field of electricity, there is an increasing need to control and manage it. This requires special purposeful devices. Electromagnetic contactors became the most demanded devices. Some of them are used to link individual elements of various schemes.
Description of the machine
The term "contactors" refers to remote control devices that perform the functions of closing and opening power lines under stable operating conditions. These devices have been widely used and are the main connecting nodes in automated electric drive circuits.
Previously, such contactors were used to control and monitor the engines of railway electric locomotives and other similar units. At present, they are often used in electronics and daily household power supply.
Depending on the speciesIn the drive switching system, there are electromagnetic, pneumatic and hydraulic contactors. The basis of contact and arc extinguishing systems, the kinematics of mechanisms and other parts are similar in their fundamental action in these devices.
According to the periodic frequency of closing and opening of the line in a certain period of time, contactors are divided into classes marked 0.3, 1.3, 10, 30. These indicators correspond to a frequency of 30, 120, 1200 and 3600 circuits / openings within 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 rated 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 rated voltage of the electric coil including (from 12 V to 440 in the AC network, from 12 to 660 V in the AC line at a frequency of 50 Hz and in the AC voltage network from 24 to 660 V with 60 Hz frequency);
- by the presence of secondary contacts (with or without contacts).
Electromagnetic contactor-starters are also divided by the type of switching of the conductors of the main line and the control line, by installation methods, by methods of connecting third-partyconductors and so on.
These parameters are only assigned to devices that were manufactured in an industrial plant.
Function of contactors
Stable performance of the device is determined when the voltage at the junction of the main line is up to 1, 1 and the control line from 0.85 to 1.1 of the calculated voltage of these circuits. Also open is the tolerance for normal operation of the contactor during the reduction of the AC voltage 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 possible position and during the voltage drop it should not delay it.
Modifications of electromagnetic contactors produced in the industrial field are designed for operation in various climatic zones, with various influences, which are determined by the location during operation, 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 flow 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 mobile contact approaches the fixed contact. The power circuit is being switched.
The main thing in the wiring diagram of electromagnetic contactors is to follow the correct sequence. Be sure to strictly follow the safety rules when working with electrical appliances. Do not make any manipulations with operational units that are energized.
Opening is characterized by a voltage drop from the coil. There is a disconnection of closed contacts due to the action of gravity of the moving parts and the straightening of the return spring.
Device design
Electromagnetic contactor includes such main functioning elements as main contacts, arcing and electromagnetic system, secondary help contacts.
The main contacts perform the task of closing/opening the power line. Their operational capabilities are designed for long-term energization, a huge number of operating moments on / off with the highest frequency of execution.
The normal state of the contacts is determined when the pull-in coil is not energized, and all mechanical latches are in the free state. The main contacts can be lever or bridge type. Lever-type contacts have a moving system with swivel capabilities, while bridge-type contacts have a forward-moving system.
Electric arc extinguishing system
The arc-extinguishing design directly extinguishes the electric arc that 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.
Arc data boxesDC devices are designed on the principle of arc suppression by means of a magnetic field in compartments with longitudinal slots. The field of a magnetic nature, in the main number of models, is excited by an arcing coil connected in turn with the contacts.
Selection of contactors
MK series electromagnetic contactors are used in rail-based vehicles, trolleybuses and large industrial fixed installations. 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 should follow the technical requirements as follows:
- area of use and purpose of operation;
- application category;
- stability in terms of mechanics and commutation;
- number of contact group in electromagnetic contactors;
- type of current and power of rated voltage, including the main circuit;
- rated voltage and required coil power;
- climatic conditions and operating procedures.
Cost of appliances
Contactors on the electrical goods market are sold at different prices. It depends on the technical characteristics, models and modifications, conditions and modes of use and the manufacturer's company. For example, the price of an electromagnetic contactor for 4 kW AC fluctuates inaround 1000 rubles, and the contactor model KT-6023 will already cost about 6300 rubles.
