In old houses built back in Soviet times, in apartments directly below the electric meter there was a packet switch, or simply a bag. For some hosts, this device still works properly, and is used for its intended purpose. With the help of electrical components, the phase voltage and zero are connected to the electric meter and then, through linear automata, they are distributed throughout the apartment. This device duplicates the functions of the input circuit breaker, which allows you to refuse to install it in the switchboard, connecting the phase and zero directly to the meter terminals.
What is a packet switch
Despite the apparent archaism, the packet switch is still used in electrical circuits. In its structure, it is a purely mechanical device, manually controlled with some effort. The complexity of its switching is explained by powerful springs that fix the moving part in each of the working positions.
When it is turned in any direction, two groups of mechanical contacts are closed, and with a further half-turn, they also open. When connecting an apartment, for example, one pair of connectors breaks (closes) the phase supply circuit to the electricity meter. At the same time, the second pair does the same with zero core. Therefore, in terms of its scheme and functional purpose, the bag installed in front of the electric meter is essentially an introductory device.
Classification and labeling
Known samples of bags differ in the following characteristic features:
- by the method of attaching lead wires;
- in terms of climate protection;
- according to the features of the switching mechanism.
In accordance with the place where the wires are connected, such a switch has two versions: with front or rear connection. According to the degree of protection of internal spaces, open models are distinguished, as well as partially or completely sealed products. By design features, the switching mechanisms are divided into batch devices (cam) and drum type.
Regardless of the design, such switches have almost the same technical parameters and have the same drawbacks. For example, the resource of the spring mechanism of most models is not more than 103 commutations.
There are wear-resistant samples designed for a wider range of switching (200-1000). The main condition for extending the working life of contact springs is the frequency of their use should not exceed 50 times per hour.
When marking products of this class, the following alphanumeric designations are used:
- the presence of the icon "B" means the switch;
- if there is a “P” sign on the case - this means a switch (or packet);
- the letter "G" means sealed;
- digits 1-4 correspond to the number of poles;
- “N” is the direction with positions 2, 3, 4, and “P” is the reverse.
The designation of the device must indicate the degree of protection, as well as the type, installation features and rated current. On some models, badges are applied that indicate the material of the product body: heat-resistant plastic or silumin.
Design Features
Arranged electric bags are very simple. They include the following nodes:
- product body;
- contact mechanical group;
- shift mechanism;
- rotary knob.
When considering the details of the switch, one should take into account its design, according to which it can be cam or disk. The working units of the first of these modifications have fixed contacts fixed on a square substrate isolated from the housing. The movable node of the contact group is made in the form of knives that are retractable and extendable during switching by means of a manually operated handle.
The case of the machine’s electrical components is made in the form of a prefabricated structure consisting of electrical insulating washers, fastened together by means of pins of a special shape. When introducing knives, the contact terminals enter the spring-loaded grooves of the switching mechanism. When the handle is turned one quarter of a turn, the fixed and moving parts of the circuit breaker close together. Their progress is limited by the special emphasis available on the cover of the device.
The disk switch, unlike the cam mechanism considered, works according to a different principle. It turns on and off with one turn of the control knob strictly 90 degrees. The specificity of this device is the location of the control handle, which is always in one of two positions (this, in principle, distinguishes it from the cam variety).
Due to the simplicity of the mechanism, as well as the comparative convenience of switching, packet switches and switches are still widely used in the following areas:
- as input switches;
- to switch control chains;
- as pure distribution switchgears;
- in starting circuits of electric motors for various purposes (in ventilation systems, for example).
There are several varieties of batch machines designed for operation in a wide variety of climatic conditions, including explosion-proof execution. They are installed in particularly humid rooms, as well as in technological niches and entrance shields provided for by the development project.
Advantages and disadvantages
The attractiveness of switching devices is explained by a number of their advantages:
- compactness, greatly simplifying the installation of the device and ease of use;
- rapid extinction of the electric arc in three-phase 380V electric bags, due to the rational design of the working chamber;
- ease of maintenance;
- mechanical stability;
- universality of application.
Packets are able to work in conditions of strong temperature drops (in the range from -40 to 70 degrees). Products with a sealed enclosure are reliably protected from dust and moisture.
The disadvantages include a small resource in the number of maximum switching and complete unsuitability for repair. In the event of a breakdown, they are simply replaced with new products.
Updated instrument analogs
Outdated models of bags installed in switchboards are everywhere replaced by more convenient and reliable automatic machines. This is due to the fact that the requirements for the efficiency of such devices have changed. They must combine the capabilities of RCDs, simple and differential machines, and sometimes contactors when installed in 380 volt power circuits. Before connecting the protective device, you will need to familiarize yourself with the features of each of the designated functions.
RCD and automatic
When operating in the RCD mode, the device guarantees protection of a person from damage by high voltage. It reacts to the differential current that occurs when leaks occur in emergency circuits that can lead to a short circuit, as well as a fire to the wiring. In a dangerous situation, the device simply shuts off the electrical network and prevents the further development of unwanted events.To monitor its performance on the case there is a special button with the designation "Test".
Today, automatic vending machines completely replaced the old-style circuit breakers. They perform similar functions, but are more convenient in operation, durable and are characterized by increased wear resistance. When used correctly, they are able to selectively perform their functions, guaranteeing a quick disconnection of the hazardous circuit with a minimum time delay.
Difavtomat
Difavtomat is a universal device that combines the functions of an RCD and a conventional AB. It completely replaces the package switches installed not only in household power networks, but also in enterprises. In other words, the difavtomat is “2 devices in one”, combined in a common housing. This device copes well with both functions, differing in small dimensions and easy handling.
Contactor (powerful electronic relay)
Devices such as contactors are used when it is necessary to switch electrical circuits with currents up to hundreds of amperes. A feature of these devices is the ability to control switching modes at remote distances. Electromagnetic relays do not respond to leakage currents, since they are designed only for their rated values. In this they are significantly different from conventional circuit breakers. Such devices are traditionally installed in the mechanisms of elevators, in electric vehicles, as well as in industrial equipment.
In modern conditions, it does not make sense to install obsolete models of package switches in place of input automatic machines. For these purposes, reliable and easy-to-use automatic devices with enhanced functionality are better suited. However, this brand of switching devices is indispensable in other places where it is necessary to manually remove the power during installation operations, for example.
