The designation of the relay on the diagrams or in letter form is necessary so that qualified specialists can easily find it. As already mentioned, in the case of the letter designation, K. is used. However, it will be fair to say that there are such drawings as electrical schematics or just electric ones that do not use alphabetic names. In this case, the symbol of the relay in graphical form is used. Then the relay will be described as a rectangle, from the large sides of which one contact moves away.
What is rel
A relay is a switching device, or simply KU. The main purpose of this item is to connect or disconnect the circuit of an electrical or electronic circuit if the input current values change in a certain way. As for the scope of use, for the first time this device as a working unit was used in a telegraph. Use in electronic and electrical circuits came much later.
Equipment device
It is worth saying that the designation of the relay in the letter form K is rarely used, since today there are many different types of this device, and they have a different designation. However, the initial device of these devices is approximately the same.
A relay is a coil that has a non-magnetic base. A copper wire with insulation made of fabric or synthetics is wound on this base. However, dielectric varnish is most often used. Inside the coil, which stands on a non-conductive base, a metal core is placed. In addition, there are parts such as springs, anchor, contacts and connecting elements.
If the letter designation of the relay is only one letter K, then the principle of operation of this device is as follows. When current is applied to the coil of the solenoid, the core will begin to attract the armature. Since the elements are metal, when they are connected, a circuit will be closed. If the current strength begins to weaken, then at a certain level the spring force will become larger, because of which it will push the armature back, and the circuit will open. The relay itself will work quite abruptly. To increase the smoothness and accuracy of work, resistors are usually added to the circuit, and capacitors are used to protect the device from any surges.
In short, the designation of the relay by the letter K means that this is the simplest equipment that works on the principle of the simplest electromagnetic induction. Due to a fairly simple way of working, it is considered very reliable.
Relay characteristics
This device has several basic characteristics that you should pay attention to.
- A parameter such as sensitivity is very important. It will determine how much current is needed for the relay to trip.
- There is such a characteristic as the resistance of the winding of an electromagnet.
- Each device has its own threshold for turning on and off the circuit. In other words, each relay has its own minimum current value for tripping and opening.
- There is such a characteristic as the time of attraction and the time of repulsion of the anchor.
Electromagnetic relay
One of the most common varieties is an electromagnetic relay. This KU belongs to the electromechanical type, and the principle of operation is based on the fact that the magnetic field that is created in the static type winding interacts with the anchor. Such devices, in turn, are divided into two types. The first is electromagnetic, which respond only to the amount of incoming current. The second is polarized, for which both the incoming current and its polarity are important. As for the letter designation of the relay, here you can still leave the letter K. If we talk about the application, then most often they are used in control circuits. In industry, such devices are in an intermediate position between high-current devices and low-current ones.
KU with alternating current type
As you can see from the name, the operation of this type of relay occurs when AC is applied to the input terminals. As for the designation of the voltage relay, it is often referred to as KV. This marking is applicable to almost all types, since almost all of them work with the input current and its voltage.
As for the AC KU, this is a device that has control of the phase transition through zero or without it. The equipment is an integral assembly of modules such as a thyristor unit, rectifier diode unit, and control circuits. It is also worth noting that they can be of two types, differing in the modular base on which they are made. There may be types with transformer or optical isolation. As for the application, then, of course, they are used in variable networks with a maximum voltage of 1.6 kW. As for the current, its value should not exceed 320 A.
Separately, it is worth mentioning devices that are designed for 220 V networks , since they cannot function without such devices. Such devices are used if there is a need for closing or opening contacts of multidirectional type. An example is a device that illuminates the terrain and has a motion sensor. Then it turns out that one of the inputs is connected to the power supply, and the other to the sensor.
DC KU
In addition to such devices, such as time switches are used, the designation of which is KT.
The DC switching device can be polarized or neutral type. The difference is that polarized devices are sensitive to the polarity of the input voltage. Depending on these poles, the KU anchor can change its direction of movement. Neutral ones do not depend on this parameter. Most often, such devices are used only if it is not possible to connect to an alternating current network.
This is due to the fact that the cost of such devices is higher than with alternating current, as well as the need to connect a power supply for normal operation.
Electronic type device
In addition to current devices, there are also electronic or thermal types. For example, the designation of the thermal relay KK. The scope of its application is also quite clear, which follows from the name. More worth paying attention to electronic devices.
As for the design and principle of operation, they are not too different from electromechanical ones. A significant difference lies in the fact that to perform all the necessary functions in this case, a semiconductor type diode is used. The most common use of such devices is in vehicles, where most of the functions are performed using electronic relay control units. It is still not possible to completely abandon their use.
Device manufacturers
To date, there are many companies that are engaged in the production of such products, but pay attention to only a few of them.
For example, among European manufacturers, the third place is occupied by a company from Germany called Finder. She is engaged in the production of devices such as general purpose relays, solid state, power, time relays. There is also a pressure switch, the designation of which is KP.
If we talk about domestic manufacturers, we can distinguish JSC NPK "Northern Dawn". This company produces anchor electromagnetic switching-type models. The main purpose is industrial and special areas of industry. As for the designation of the relay, then in this case it is K, since they belong to the general type.
There are manufacturers from Japan. The company is called Omran and manufactures devices such as solid state and electromechanical relays . In addition, products such as low-voltage switching devices are also manufactured.
Leading lines have long been held by products from the American company American Zettler. The company produces about 40 different types of KU, which are suitable for a variety of purposes.