Auxiliary contact blocks are also called contactors and are used to open and close an electrical circuit. This functionality is used regularly: from the usual switching on of lighting devices to the control of large-sized units used in the industrial field. Therefore, depending on the complexity of the functions performed, additional requirements will be imposed on the contactors. But, nevertheless, the selection criteria in relation to them are the same. You should pay attention to them in order to avoid mistakes when choosing a product.
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The peculiarity of such devices is that structures of this type are capable of conscientiously and efficiently performing the assigned tasks and the function assigned to them - to control all kinds of units and systems at a certain distance. It is not for nothing that it is called a "contactor", since it must be in contact with something. From the point of view of science, the main task is to switch direct and alternating current. They are installed not in the immediate vicinity, but at a certain distance from the automatic control object.
The first such devices were used exclusively for turning on and off. Currently, the field of application has expanded significantly, thanks to a huge number of additional devices (attachments and accessories), which include time relays and thermal relays (control occurs at a certain temperature), additional contact groups, and so on.
Thermal relays are installed in shopping centers and other large public places where large areas are filled with a huge number of people. The contactor configured for cooling will turn on when the temperature at the facility reaches the set point, for example, +25 degrees. This will turn on ventilation. The device will work in the opposite direction if the air temperature drops to +18 degrees. Then the contactor will switch off and ventilation of the premises will stop.
A unique device is a time relay. It helps relieve a person from the daily power on and off in public places. If you set the appropriate parameters for the product: turn off at 23-00, turn on at 6-00, then it is at this time that such actions will be performed, without human intervention. The equipment will work without interruption for a long time. It is enough to set the required parameters.
Modular contactors are considered to be the most common and in demand. Their main feature is that they are mounted on a DIN rail. The manufacturer produces them in two standards:
They differ from each other in their rated breaking capacity. In the first version, it is from 4.5 to 6 kiloamperes, in the second - 10 kiloamperes. This suggests that high power equipment will need a larger coil than low power equipment. What are the types of industrial units? Only 22.5mm. And the modules are considered contactors 17.5 mm. They are designed for switching low inductive loads with a low current rate (from 24 to 400 V, 50 Hz). They are used for elementary automatic processes:
It should be borne in mind that there are inexpensive popular models that, in terms of their functions, durability and quality, are not inferior to their eminent brothers, which are sold at a significant price.
How to choose the most suitable option? Don't immediately pay attention to how much it costs. This is not the main, and by no means the only indicator from which it is worth starting from. First of all, attention should be paid to such an important characteristic as the indicator of the rated operating current. For domestic needs, a range of 20 to 63 amp is sufficient.
Electrical durability should not be overlooked either. A quality product has an indicator of 30,000 cycles or more. This means that exactly as many times, and no less, the contactor can be switched on and off. A low-quality product will not withstand such a load and will quickly fail. What does this indicator testify to? First of all, about the presence of high-quality contacts in the product, which are able to withstand such a huge number of cycles. The average price of such products is substantial.
Retail outlets, including online stores, were flooded with budget products from unknown manufacturers. According to buyers, its purchase should be approached with extreme caution. As a rule, it is made of low-quality material, so the reviews about it are the most negative. They do not even reach the end of the warranty period. How to protect yourself from losing money, and which device is better to buy?
First, it is necessary to make an overview of popular models, the manufacturers of which have been on the market for a long time and have gained deserved popularity. It would be good to first study the rating of high-quality devices, their types, advantages and disadvantages, additional functions, design features.
The weight of the goods also plays an important role, which cannot be determined by ordering it online. When visiting a specialized store, ask the seller to give you some contactors to hold in your hands. Try to figure out which one is the most difficult. The presence of copper has a great influence on weight. The more it is, the better the contacts are and the better and more durable the purchased device will work.
Indicators | Description |
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Voltage and rated current | The indicator of the maximum permissible load plays an important role. For this purpose, it is necessary to calculate the current indicator in the switched circuit and then the appropriate device is selected. The voltage in the electromagnetic coil should not exceed the voltage in the switched circuit, it is desirable that it coincide. Therefore, manufacturers produce units with coils of 220 or 380 V. If relays or sensors with lower voltage are used in the circuits, then you should pay attention to a contactor with the same coil voltage. |
Mechanical and switching durability | The device should work without a malfunction, turn on and off with high quality and in a timely manner during the entire number of cycles. This is the responsibility of such an indicator as durability. All units are divided into the following types: A (highest), B (average), B (lowest). This indicator assumes that no breakdowns are expected during the warranty period. |
Number of poles | The use in three-phase networks involves the installation of contactors with 3 working poles and one additional one, which can be used for interlocking to fix the "on" position.Poles can be from 1 to 5, depending on the AC or DC current and the number of phases with which the contactor will work. The number of contacts can be increased thanks to special attachments. This makes it possible to use the device in the most complex circuits and processes. |
Degree of protection | Depends on operating conditions. If the contactor is located in a protected electrical cabinet, then you can opt for the degree of protection IP20 and even less. If the operation takes place in unfavorable conditions, then the indicator should correspond to IP54 or IP65. This level corresponds to industrial premises where there is too much dust and high humidity. If there is a possibility of overloads, then it is worth additionally purchasing instantaneous power protection equipment with a thermal relay. |
The installation of such contactors is carried out, as a rule, during the construction of facilities, when it comes time to do electrical work. It is possible to install a block of auxiliary contactors and during the repair of the power supply system, if necessary. Where to buy protective automatics? Best in specialized stores.
If you have certain knowledge and skills, you can install automation at home and with your own hands, after consulting with professional craftsmen or by studying the step-by-step instructions available in the public domain. Self-installation of protective automatics will cost less than the services of professional craftsmen.
A successful device of Russian production, which is advised to be used by both professionals and ordinary consumers. Produced in a good housing, which does not get moisture and dust. The control network - AC, operates at a maximum voltage of 400 V.
The average cost is 1120 rubles.
Used for Osmoz heads, for a screw, for a complete set of push-button posts. Mounts to the base of the contact block. No backlight provided. Operates at a rated voltage of 690 V, 50 Hz.
The average cost is 174 rubles.
Partly integrated beautiful French-made machine. Mostly used at home. It has excellent technical characteristics, is made of high quality materials using a solid base, which allows the equipment to be used in absolutely any conditions. It has a screw connection, one changeover contact, one normally open contact, one normally closed contact.
Certified products can be purchased for 2300 rubles.
The low voltage device is connected via a screw connection. The number of normally closed and open connections is one each. It works with AC current, which is a clear advantage, since it can be used in various fields. It is mounted on top of the rail, which is very convenient. It is produced mainly for home use.
The average price of a product is 1300 rubles.
The high-quality product is installed in signaling units. Has a connection type - screw connection. Functions with AC current. There are normally closed and open contacts in the amount of 1 pc. each. Fits front to front.
The average cost is 900 rubles.
A block of quality auxiliary contacts at an affordable price. Top mounted with screw connection. The number of changeover contacts is 2 pieces. Highly functional and easy to design, assemble and operate.
You can purchase it at a price of 2236 rubles.
The manufacturer offers quality products at an affordable price. Top mount, screw type connection, two normally open contacts. Works with AC current.
The product can be purchased at a price of 1250 rubles.
Quality product with excellent functionality. Convenient in installation and operation and does not require frequent maintenance. Belongs to the category of partially integrated. The number of normally open and closed contacts is two each. Frontal installation is provided.
The average price for a product is 414 rubles.
It is a block of auxiliary contacts with screw terminals. Specifications:
Products can be purchased at a cost of 800 rubles.
High-quality, instant-action products. Installation method - from the side. Operates at a rated operating voltage of 690 V. Mechanical durability is noted at three million cycles. The minimum switching current is 5 mA, the minimum switching voltage is 17 V.
The average price is 1350 rubles.
Czech products for modular machine. Used to close electrical circuits. Has a quality certificate. The degree of protection is IP20, but it is possible, at the request of the buyer, to supply a housing that is able to provide protection to IP 40. It is mounted on a DIN rail or on a panel. The manufacturer provides a warranty for the goods up to 5 years.
The average price of a product is 1333 rubles.
Convenient top-mounted model. A screw type connection is used. It has three normally open contacts and one normally closed contact.
Price - 850 rubles.
Used to close electrical circuits. The manufacturer provides a quality certificate and a 5-year warranty. It has IP20 protection, but at the customer's request it can be increased to IP40 for all contactor terminals. Attaches to a panel or DIN rail.This product is very popular with professional electricians. It can be purchased at an affordable price of 5,000 rubles.
The manufacturer guarantees high-quality and durable assembly, therefore this product is in great demand among professionals. In the manufacture of the case, high-quality plastic is used, which does not ignite when ignited, but only begins to melt. Top-mounted with screw connection. Has four normally closed contacts.
Price - 2200 rubles.
Partially integrated product with screw connection and frontal front installation. There are four normally open contacts. It is widely used both in production and at home.
Price - 1533 rubles.
The manufacturer produces high quality products with good functionality. The housing is made of a flammable material, so the fire is excluded. Fits front to front. There are four normally open contacts.
The average price is 2200 rubles.
Auxiliary contact block for professional electricians. The manufacturer guaranteed high quality and an optimal price of 1100 rubles. The device has a screw connection, is mounted from the top, and there are four normally closed contacts.
The product is distinguished by good functionality, decent quality, guaranteed long service life. It is used in various fields. Has a screw connection, four normally closed and the same number of normally open contacts. Works with a power switch.
The product can be purchased at a price of 25,400 rubles.
When choosing a contactor, the main thing is not to give preference to low cost. It is worth remembering that a quality product will never cost a penny. Also discard the units of dubious brands. These can be cheap fakes that will not even last the warranty period. It is best to pay attention to the products of global commodity producers, even if you have to overpay for the name a little. But you will definitely know that the purchased device will be reliable, durable, of high quality, and you will not need to change it every year for a new one, spending additional funds.