Electric busbars are needed to connect individual elements of electrical installations into a single whole.
Definition
Electrical connecting tires allow you to combine all the elements of the electrical installation into one. In fact, these are conductors whose resistance is at a low level.
When several tires are combined at one point, they talk about busbars. As a rule, they are installed on insulators, which simultaneously serve as supports. He hides in a special box (channel). Thanks to this, it is protected from environmental factors. The busbar trunking must always be resistant to the resulting dynamic and thermal loads, surge currents of the mains.
Electric busbars are available in several designs. For their division into types, several classifications are provided.
According to the method of execution, flexible and rigid tires are distinguished. They are also called flat and tubular. Flexible tires do not twist. They should not have a high degree of gravity. Moreover, the degree of tension of all wires should be the same. Under the influence of temperature, the length of the tire may change. Therefore, rigid models are equippedflexible jumpers that should compensate for these changes. In addition, they are equipped with vibration dampers.
In addition, busbars can be insulated or non-insulated. Already from the name it is clear that in the first case the tire has an insulation layer, and in the second case it does not.
Classification of tires by section shape
According to the shape of the cross section, busbars are divided into the following types:
Tubular
Rectangular
Boxed
Two-way
Three-way
Square flat tires dissipate heat well. Their use is advisable in a network with a large current strength (from 2 thousand to 4.1 thousand amperes). In such cases, they are combined into groups of several pieces. This creates a two- or three-lane bus.
Busbars have a number of disadvantages:
Difficult to install
Inductive current that is unevenly distributed
Poor mechanical strength
Reduced cooling capacity
Low short circuit resistance
In a network with a voltage of 10-35 kilovolts, box-shaped or flat products can be used. The most effective is tubular. It has a number of advantages. It is durable and conducts heat well. The electric field around it is distributed evenly. Due to this, coronation does not appear.
Types of tire material
Depending on the material from whicha tire is being produced, the following electric tires are distinguished:
Copper
Aluminum
Steel
Steel-aluminum
The last option is a core made of galvanized steel wires around which aluminum wires are wound.
Aluminum tires have the following advantages:
Resistant to corrosion
High electrical conductivity
Light weight
Their cost is lower than other types
Ductile grades of aluminum with a minimum amount of impurities are used for their production. Low alloys of aluminium, magnesium and silicon can be used. Additional elements allow you to increase strength, ductility, elasticity.
Copper bars can contain up to 99.9% copper. Such products are labeled M1. Widely used grades are ShMT and ShMTV, which are produced from an oxygen-free grade. They differ in the degree of softness. The first two letters of the ShMM and ShMT markings mean "Copper bus". The letter "M" that follows characterizes soft products, "T" - hard.
Marking for three-phase alternating current
Identify the elements of electrical installations will help "tips", which are expressed in the color and letter designation of tires and wires. They are not chosen randomly. They are regulated by standards.
There are two ways to color code tires. The first implies that the marking of electric busbars is applied at the stagemanufacturing. The manufacturer uses insulation of different colors. The second is suitable in cases where the product has one color. In such situations, colored electrical tape is used to mark different phases.
In the case of a three-phase current, the marking will look like this:
Phase A turns yellow
Phase "B" is colored green
Phase "C" is colored red
Designation of conductors
The grounding conductor is marked PE. It is always indicated in yellow-green. Colors go in longitudinal lines. Moreover, the use of these two colors separately is prohibited by GOST. For the neutral and middle conductor (working) marked N, blue color is used.
When connecting zero protective and working conductors, all three colors are combined. The marking in this case looks like PEN. The conductor is made in blue, and at its end and at the junctions a strip of yellow-green color is made. At present, the opposite coloration is also acceptable: a yellow-green conductor with a blue stripe at the end.
Letter marks
Correctly read the diagram, determine the type of bus or wire will help letter designation. Like colors, letters have their own meaning.
Electric wires and buses with alternating current are decoded as follows:
L is a conductor of a single-phase network
L with the numbers 1, 2 or 3 - a conductor in a three-phasenetwork
N - neutral conductor (or neutral)
M is the middle conductor
PE - grounding conductor (protective)
PEN - combined neutral conductors (protective and working)
With direct current, the symbols will look like this:
L+ – positive (or positive) conductor
L- - negative (or negative) conductor
All of these markings and designations are mandatory. They are regulated by the adopted regulations.
It's hard to remember all this at once. But an experienced electrician knows all this. This marking will allow you to determine where and what is connected. And this will be enough for a simple person to understand, for example, what kind of bus is needed for electric machines. It may be needed when repairing electrical wiring in the house. It is easy to connect additional sources to it later.
