An introductory machine or VA is a circuit breaker for supplying electricity to the “end user”, provided that a short circuit or overload has occurred. With the exception of the introductory machine, fuses, a circuit breaker or a batch switch can also be installed on the floor switchboard, but in comparison with them, it is characterized by a large value of the rated current.
Types of ratings of circuit breakers
The full name of the device is an opening circuit breaker. Before setting the ratings of machines, it is important to learn about the features of their work. Due to its proximity to the overhead line, the equipment should have increased switching resistance, which is characterized by unhindered and quick operation of the device in case of emergency situations. All indicators are recorded on the equipment labeling.
The supply of electricity to the apartment depends on the circuit of the electric network and its needs. Based on the characteristic features, it is necessary to select the appropriate ratings of the current machines.
Single pole
This variety is used in a single phase electrical network. Through the upper terminal, the device is connected to power, and the lower terminal connects it to the outgoing wire.
Mount it in the place where the phase wire is broken. In the event of an emergency, it disconnects the cable from the power supply. The principle of operation is similar to machines that are installed on the outgoing lines, only the rated current is higher (40 A).
The input machine installed in front of the electric meter must be sealed. The cable for entering the apartment from overheating also protects the VA.
Bipolar
The bipolar is somewhat different from its predecessor and consists of a block with two poles. They are equipped with one combined lever, which is capable of blocking all shutdown mechanisms. This feature in the work is extremely important, since it is unacceptable to subject the neutral wire to rupture.
You cannot install two single-pole devices instead of one two-terminal device. The desired result can still not be achieved, and in emergency situations, the likelihood increases that all household appliances will fail.
Mounted with single-phase input, this is due to the specific scheme of connecting electricity in old-style houses. From the riser of the electrical panel at the entrance to the apartment, a branch is made using a single-phase two-wire line.
To ensure a 100% guarantee of shutdown, de-energize the apartment shield using a two-terminal device. In addition, quite often it is necessary to change the packet switch in the entrance flap.
Another significant reason for installing a two-pole input circuit breaker is the replacement of plugs. On the old shields there are still plugs that are installed at zero and phase. The wiring diagram remains the same.
Three-pole
A device for a three-phase network is used to ensure simultaneous de-energization of all phases during a short circuit or overload of the internal electrical network.
Basic concepts of rated circuit breaker currents
The rated current is the maximum current capacity that the thermal release is not able to respond to. They select it, relying on the listed selection criteria:
- Peak (maximum allowable) load on the line or the estimated total network power when a large number of household appliances and other electrical appliances are operating at the same time.
- Cable cross-sectional area is the cut-off area, which is sufficient to allow a certain load to pass through itself and at the same time not to overheat.
It is always more worthwhile to pay attention to the cable cross-section, since it is strictly forbidden to put more protection than the cable can safely pass through. If you neglect this feature, the cable will become very hot, which can lead to an emergency.
Calculation of machine values
Based on the fact that the cable cross-section and maximum load are closely interconnected, knowing at least one parameter, you can easily calculate the rest. For convenience, it is recommended to use the selection table for connection and power.
| Rated current | Conductor cross section | Voltage | |
| 380 V | 220 V | ||
| 1 A | 0.5 mm2 | – | 2.4 kW |
| 15 A | 0.75 mm2 | – | 3.3 kW |
| 17 A | 1 mm2 | 11 kW | 3,7 kW |
| 23 A | 1.5 mm2 | 15 kW | 5 kW |
| 30 A | 2.5 mm2 | 19 kW | 6.6 kW |
| 41 A | 4 mm sq. | 26 kW | 9 kW |
Criterias of choice
Each electrical network, house or apartment, is individual and has its own characteristics. There are no standard solutions for installing circuit breakers. When choosing a device, it is important to consider all selection criteria, otherwise it is possible to create an emergency.
The principle of intra-apartment wiring
Internal electrical cables have a branched structure called a graph without cycles. Thanks to this construction principle, it is possible to equip all types of chains with protective functions.
This approach made it possible to increase the stability of the entire system when creating an emergency, and also simplifies the process of eliminating breakdowns. The load is evenly distributed.
The total power of electrical appliances
The maximum possible and permissible load on the circuit is observed with the simultaneous inclusion of all electrical appliances in the apartment. To calculate this indicator, it is enough to simply sum the total energy consumed per unit of time.
There are lines for which simultaneous operation of all devices is not possible. Sometimes houses are specially equipped with systems that block the operation of powerful devices.
Core section selection
Before installing the power electric cable from the distribution panel, it is necessary to calculate the power of all electrical appliances. The cross-sectional area of any branch is selected according to the calculation table, taking into account the material of manufacture of the wiring, for example, copper and aluminum.
Electrical cable manufacturers include the most detailed reference materials in their products. If for some reason the information is not available, you need to refer to the data from the directory under the title "Rules for the installation of electrical equipment."
Sometimes consumers, in order to protect themselves, choose not the minimum allowable cross-sectional area, but with a small margin. This is justified for the following reasons:
- The start of electrical appliances with powerful electric motors, which gives strong starting currents. This process is accompanied by a strong voltage drop, which can lead to serious breakdowns in the electronics of washing machines, air conditioners, etc. The thicker the conductive cable, the fewer voltage surges.
- Long-term operation of a thick cable that is periodically subjected to maximum permissible loads. To re-lay the wiring in the apartment is a troublesome thing, especially if the rooms have already been properly renovated.
- Large bandwidth allows you to connect new electrical appliances to the network branches.For example, in the kitchen you can install an electric oven or a freezer.
The ratings of current circuit breakers, subject to all the rules for installation, maintenance and operation, significantly extend the life of household appliances and other electrical appliances.
