How to accurately choose the power cord of the refrigeration equipment

How to accurately choose the power cord of the refrigeration equipment The installation of refrigeration equipment is a very rigorous work, and its installation situation will affect the work of the machine to a large extent. Therefore, when installing, the engineer needs to choose a suitable power cord. But the choice of power cord is actually a science. If you choose a big one, it will cause economic waste. If you choose a small one, there will be safety hazards. How big is it to be safe and economical? This article discusses the selection of power wiring for refrigeration equipment.

　　What is wire and cable

　　 definition of wire and cable:

Wires and cables are used to transmit electrical (magnetic) energy, information, and realize the conversion of electromagnetic energy. Wires and cables in a broad sense are also referred to as cables for short. Cables in a narrow sense refer to insulated cables, which can be defined as a collection of the following parts: One or more insulated cores, as well as their respective possible coating layers, total protective layer and outer protective layer. The cable can also have additional non-insulated conductors to transmit electrical (magnetic) energy, information and wire products for electromagnetic energy conversion.

The basic structure of wire and cable:

　　1. Conductor: An object that conducts current. The specifications of wires and cables are expressed by the cross-section of the conductor.

　　 2. Insulation: The outer insulating material is based on its withstand voltage.

　　 Classification of wires and cables:

　　 1. According to the voltage level:

　　 (1) Low-voltage cables: suitable for fixed laying on power transmission and distribution lines with AC 50Hz, rated voltage 3KV and below for power transmission.

　　 (2) Medium and low voltage cables: generally refers to cables of 35KV and below, such as polyvinyl chloride insulated cables, polyethylene insulated cables, and cross-linked polyethylene insulated cables.

　　 (3) High-voltage cables: generally 110KV and above cables, such as polyethylene cables and cross-linked polyethylene insulated cables.

　　 (4) Extra high voltage cable: 275～800KV cable.

　　 (5) UHV cables: cables of 1000KV and above.

　　 2. According to insulation materials:

　　 (1) Oil-impregnated paper-insulated power cables are insulated power cables with oil-impregnated paper. Its application history is long, safe and reliable, long service life and low price. The main disadvantage is that the laying is limited by the drop. Since the development of non-drip paper-impregnated insulation, the problem of drop limitation has been solved, and oil-impregnated paper-insulated cables have continued to be widely used.

　　 (2) Plastic insulated power cables whose insulation layer is extruded plastic power cables. Commonly used plastics are polyvinyl chloride, polyethylene, and cross-linked polyethylene. Plastic cables are simple in structure, convenient in manufacturing and processing, light in weight, convenient in laying and installation, and not restricted by the laying drop. Therefore, they are widely used as medium and low voltage cables and have a tendency to replace viscous-impregnated oil paper cables. The disadvantage of its large z* is the existence of tree-like breakdown, which limits its use at higher voltages.

　　 (3) Rubber insulated power cable insulation layer is made of rubber plus various compounding agents, which are fully mixed and extruded on the conductive core, and then heated and vulcanized. It is soft and flexible, suitable for occasions with frequent movement and small bending radius.

　　Calculation of power cord for refrigeration equipment

　　When choosing the power cord of the refrigeration equipment, in order to select the appropriate size and achieve the goal of economic safety, a simple estimation can be made. The specific calculation method can follow the cable safe working current formula:

　　 ten under five (multiply five times less than ten squares)

　　 a hundred on two (more than one hundred squares multiplied by two)

　　 two, five, three, five, four, three realms (two-five squares times four, three-five squares times three)

　　 seven zero nine five two and a half (the lines of seven zero and ninety five square are multiplied by two and a half)

　　 8 to 90% off the pipe temperature (if the line is piped or the installation environment temperature is too high, the current carrying capacity will become smaller, and the safe current value must be multiplied by 0.8 or 0.9)

　　Copper wire upgrade calculation (on the basis of the aluminum core wire of the same cross-section, an increase of one level, for example, the 2.5 copper core wire is an increase of one level from the 2.5 aluminum core wire, and it is calculated as the four square millimeter aluminum core wire)

　　Bare wire plus half (add another half on the basis of the calculated safe current number) 　　 Precise selection of power cord for refrigeration equipment

　　1, s* should first choose power cables: suitable for AC 50Hz, rated voltage 0.6/KV and below power transmission and distribution lines, for power transmission and distribution. The ambient temperature is 25℃, and the working temperature of the cable conductor does not exceed 70℃.

　　2. Commonly used power cables: VV (VLV): copper (aluminum) core PVC, insulated PVC sheathed power cables.

　　 Its safe current carrying capacity can refer to the following table for selection:

　　 Note: The above data is for reference only, and the specific current carrying capacity shall be based on the cable manufacturer purchased.