Electric buses are necessary to connect the individual elements of electrical installations into a single whole.
Definition
Electrical connection tires allow you to combine all the elements of an electrical installation into a single whole. In fact, these are conductors whose resistance is low.
With a combination of several tires 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 should always be resistant to emerging dynamic and thermal loads, shock current of the mains.
Electric buses are made in several versions. For their division into species provides several classifications.
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 traction. Moreover, the degree of tension of all wires should be the same. Due to temperature, tire lengths may vary. Therefore, rigid models are equipped with flexible jumpers, which should compensate for these changes. In addition, they are equipped with vibration dampers.
In addition, busbars can be insulated and non-insulated. Already from the name it is clear that in the first case the bus has an insulation layer, and in the second - no.
Sectional classification of tires
According to the cross-sectional shape, electric buses are divided into the following types:
Rectangular 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 join in groups of several pieces. In this case, a two- or three-lane bus is formed.
Busbars have several disadvantages:
- It is difficult to carry out installation work.
- Inductive current that is distributed unevenly.
- Low ability to withstand mechanical stress.
- Low resistance to short circuits.
In a network with a voltage of 10-35 kilovolts, boxed or flat products can be used. The most effective is considered tubular. It has several advantages. It is durable, removes heat well. The electric field around it is evenly distributed. Due to this, corona does not appear.
Types of material for the manufacture of tires
Depending on the material from which the tire is made, the following electric buses are distinguished:
The last option is a core made of galvanized steel wires, around which aluminum wires are twisted.
Aluminum tires have the following advantages:
- They have a high electrical conductivity.
- Their cost is lower than other types.
For their production, plastic grades of aluminum with a minimum amount of impurities are used. Can be used low alloy alloys of aluminum, magnesium and silicon. Additional elements can increase strength, ductility, elasticity.
Copper tires may contain up to 99.9% copper. Such products are marked M1. ShMT and ShMTV brands are widely used, which are made from an oxygen-free brand. They differ in the degree of softness. The first two letters of the and marking indicate "Copper busbar". The letter “M” that follows further characterizes soft products, and “T” - hard products.
Three-phase AC marking
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 by chance. They are regulated by standards.
There are two ways to color the tires. The first implies that the marking of electric tires is applied at the manufacturing stage. The manufacturer uses insulation in different colors. The second is suitable in cases where the product has one color. In such situations, color tape is used, with which different phases are noted.
In the case of three-phase current, the marking will look like this:
- Phase A is colored yellow.
- Phase B is colored green.
Conductor designation
The ground conductor is marked PE. It is always indicated in yellow-green. Colors come 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 is used.
When connecting zero protective and working conductors, all three colors are combined. The marking in this case looks like a PEN. The conductor is blue, and at its end and at the junction there is a yellow-green strip. At present, it is permissible to carry out the opposite color: a yellow-green conductor with a blue stripe at the end.
Letter marking
Correctly reading the diagram, determining the type of bus or wire will help the letter designation. Like colors, letters have their own decoding.
Wires and busbars for alternating current are decrypted as follows:
- L - conductor of a single-phase network.
- L with numbers 1, 2 or 3 - conductor in a three-phase network.
- N - neutral conductor (or neutral).
- M is the middle conductor.
- PE - grounding conductor (protective).
- PEN - combined neutral conductors (protective and working).
With a constant current designation will have the following form:
- L + - the conductor is positive (or positive).
- L- - conductor negative (or negative).
All of these markings and signs are mandatory. They are regulated by the adopted regulations.
Remembering all this at once is difficult. But an experienced electrician knows all this. Such marking will determine where and what is connected. And for an ordinary person this will be enough to understand, for example, what kind of bus is needed for automatic machines. It may be needed when repairing electrical wiring in the house. Later it is easy to connect additional sources to it.