Relay - what is it? Types of relays and their purpose

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Working processes of modern engineering equipment, electrical equipment and household appliances provide for a wide range of control options. Moreover, the stake is increasingly being placed on the automation of control with minimal operator intervention. The means of implementing such functions may be different, but the relay forms the basis of the technical base. What it is? In its standard form, this is a device with a winding, designed to close and open an electrical circuit. According to this principle, control is carried out in the simplest systems, but the segment is developing and more and more complex devices of this type are entering the market, focused on use in specific areas.

Common relay device

The simplest design includes electromagnets, an armature, as well as connecting fittings with conductors. At the moment the current flows to the magnets, the armature is brought together with the contacts, which leads to a short circuit in the circuit. A spring is used to control the current strength and convert it into mechanical action. It communicates directly with the armature, adjusting the degree of pressure on the contacts. In other words, depending on the characteristics of the current, the operating state of the device changes, and with it the control of the target equipment. For example, electromagnetic types of regulator relays provide independent control of boiler plants, pumping units and other engineering systems, turning on or off their power components. For a more accurate fixation of the circuit signals, additional elements such as resistors are also provided. At the same time, capacitors can be used to minimize the risk of damage to sensitive devices due to power surges.

Intended use

At the basic level, relays are used as a protective regulator when certain operating parameters of the system can adversely affect the condition of the equipment. A classic example is the same electromagnetic regulators that perform a kind of function of an electric filter. When an abnormal voltage or current is detected, they are automatically closed, thereby terminating the unsafe work process. That is, the protective function is basic and is provided for in almost all types of this device. But in modern variations, other tasks appear, due to the need to increase the autonomy of management. If we consider the types of relays and their purpose from the point of view of the user, then the list of tasks to be solved will include the following:

• Assessing liquid levels (in tanks, basins, flasks, etc.).
• Monitoring operating parameters such as temperature and humidity.
• Providing energy consumption data.
• Automate equipment according to sensors.

The set of functions and the means of their execution differ depending on the conditions of use of the equipment and the purpose of the target system.

Main classifications

The main principle of separation of relay devices is based on the specifics of the area of use. The basic classification distinguishes thermal, level, electrical and automotive regulators. But each group also has its own subcategories. The most extensive list of separation criteria in the segment of electrical switches. These include single- and three-phase relays, solid-state structures, intermediate devices, etc. The types of relays also differ depending on the principle of operation. There are still mechanical devices popular due to their simple design, affordable price and relatively high accuracy. In technologically advanced industries, mechanics are being replaced by programmable and digital relays provided with microcontrollers. Most clearly, the possibilities of such models are revealed in time controllers - timers, through which the user sets the intervals of equipment operation.

Types of voltage relays

Such devices can be divided into household, office and industrial. Accordingly, they focus on the maintenance of household electrical appliances, office equipment and production units (for example, processing machines and machine tools). In each case, protection against fluctuations in the network is provided. In particular, this is expressed in the filtering of voltage surges, the alignment of current indicators, the exclusion of pulsedinterference, etc. Again, depending on the application, we can talk about working in single- and three-phase power networks - respectively, the devices are divided into 220- and 380-volt.

Through the electronic control panels, the user can adjust the operating parameters of the relay. What does this mean in practice? The relay is supplied with a device with a digital interface and an LED display, which reflects the current indicators. Through the controls on the same panel, threshold values are set for monitoring the rated current, voltage, setting contact groups, switching on and off individual functional blocks of the equipment. The relay is mounted on a complete DIN rail, which in some modifications can also be connected to a home computer.

Relay timers

Also, these devices are called workflow time controllers. They are compact relays designed to set the moments of opening and closing according to specified hours and minutes. Multifunctional timers of this type provide several programmable modes that allow you to set up equipment and work configurations by week and day, indicating different connection sessions. According to the design and method of power, the following types of time relays are divided:

• Socket. Plugs directly into the 220V mains and requires no cabling.
• Wired. They can be installed in any place where the electrical circuit passes. The device is introduced into the network through contactors.
• Autonomous. Completely independent from the mains, devices powered by batteries or accumulators.

Varieties of thermal relays

Devices are designed for a wide range of protective functions, including the prevention of phase asymmetry, overloads, jamming of rotor mechanisms and starting delays. It is necessary to separate the types of thermal relays according to the voltage value, design and installation method. As for the network parameters, the rated voltage can be 220, 380 and 660 V. That is, the devices can be used even in heavy industry, serving high-power production units. The design and method of installation in the case of domestic models provides for both a separate connection and installation in combination with contactors of a suitable format. In the case of industrial devices, PML magnetic starters can also be used for remote control.

Control level relay

This unit can be based on the wiring diagram and installed via a DIN rail. But besides this, the design will include a filling control sensor. It can be used by various devices and devices that allow you to measure the level of liquids. The simplest models of such regulators are represented by float meters. When the set filling threshold is reached, the circuit opens in the electrical circuit and the equipment stops supplying the working medium. Pressure switches operate on a similar principle, the types of which are turned off by the design of the pressure gauge. He can beelectronic or mechanical. The former also act on the winding and the anchor mechanism for opening the circuit, while the latter programmatically control the workflow by starting or stopping the target units.

Relay for phase control

Another variation of the electrical network parameters controller, operating on the principle of automatic regulation. Typical models, in particular, monitor the voltage in converters and power generators. The symmetry of this quantity and the presence of current as such are evaluated. Most often, such devices are used in industrial areas to regulate the operation of asynchronous motors. Taking into account the specifics of the application, manufacturers provide a high level of protection for the relay itself. What is it in terms of structural implementation? These are the characteristics of the hull and additional shells, determined by the security class. If household regulators are labeled according to this indicator IP 20, then industrial regulators are IP 40. This degree of protection implies isolation from foreign bodies, shock resistance and the ability to use the device at temperatures from -10 to 50 degrees.

Automotive relays

Transport electrical engineering is also not complete without network regulators through which climate equipment, electronic assistants and multimedia equipment work. Such relays are installed in the dashboard or near the load, and are controlled by small buttons with thin connections. Generally, two types of automotive relays are used:

• With a pair of closing contacts.
• With three switches.

The difference lies in the fact that the “troika” at the moment of activation of the device closes to a common contact, and its pair is turned off. There are also specialized versions of automotive regulators for certain groups of equipment. For optics, for example, relays with improved sealing in the form of a compound filling are designed. This is to ensure that the switch can be located in close proximity to the headlights.

What are the criteria for choosing a device?

The basic selection principle is to correctly determine the operating ranges of the equipment. These can be voltage spectra, current strengths, temperature values, or height measurement levels. The next step is to find the best way to present the data. Traditional types of relays are guided by a minimum list of control information and practically do not give a complete picture of the workflow. The latest models can display information about the device through displays of various shapes and sizes. The most ergonomic and functional models have control panels with sensors and programmable modules. As for manufacturers, the most famous and reliable companies include ABB, SVEN, Orbis and NovAtek. The cost of devices starts from 1000-1200 rubles. The upper level is in the range of 3000-3500 rubles.

In closing

The use of electrical regulators is difficult to attribute to the domestic sphere, since they still perform specializedcontrol tasks. Nevertheless, there are areas in which ignorant people have to deal with such equipment. So, an ordinary homeowner may well be faced with the need to install an engineering relay. What it is? This is one of the most common types of electrical regulators that serve household boilers, radiators and other powerful electrical equipment. Theoretically, you can do without them, but in this case, the reliability and stability of the equipment decreases.