According to the system of photovoltaic power station, the cable can be divided into DC cable and AC cable. According to the application and environment, the classification is as follows:
First, DC cable
(1) A series cable between components and components.
(2) Parallel cables between the strings and their strings to the DC distribution box (combiner).
(3) Cable between DC distribution box and inverter.
The above cables are all DC cables. They are widely laid outdoors. They need to be protected from moisture, sun, cold, heat and UV. In some special environments, chemical substances such as acid and alkali are needed.
Second, the AC cable
(1) Connection cable from inverter to step-up transformer.
(2) Connecting cable from step-up transformer to power distribution unit.
(3) The connection cable of the power distribution device to the grid or the user.
This part of the cable is an AC load cable, and the indoor environment is laid more. It can be selected according to the general power cable selection requirements.
Third, photovoltaic special cable
A large number of DC cables in photovoltaic power plants need to be laid outdoors, and the environmental conditions are harsh. The cable materials should be determined according to UV resistance, ozone, severe temperature changes and chemical corrosion. Long-term use of ordinary material cables in such environments will result in fragile cable jackets and may even break down the cable insulation. These conditions will directly damage the cable system and increase the risk of cable short-circuit. In the medium and long term, the possibility of fire or personal injury is higher, which greatly affects the service life of the system. Therefore, it is very necessary to use PV-dedicated cables and components in photovoltaic power plants. Photovoltaic cables and components not only have the best weather resistance, UV and ozone resistance, but also withstand a wide range of temperature changes.
Fourth, the principle of cable design selection:
(1) The withstand voltage of the cable is greater than the maximum voltage of the system. For an AC cable such as a 380V output, a 450/750V cable is to be elected.
(2) The connection between the interior of the PV array and the square matrix, the rated current of the selected cable is 1.56 times of the maximum continuous current in the calculated cable.
(3) For the connection of the AC load, the rated current of the selected cable is 1.25 times the maximum continuous current in the calculated cable.
(4) The connection of the inverter, the rated current of the selected cable is 1.25 times of the maximum continuous current in the calculated cable.
(5) Consider the effect of temperature on the performance of the cable. The higher the temperature, the less the current carrying capacity of the cable. The cable should be installed in a place where ventilation and heat dissipation are possible.
(6) Consider that the voltage drop should not exceed 2%.
In the operation of the DC loop, it is often affected by various unfavorable factors to cause grounding, which makes the system unable to operate normally. Such as extrusion, poor cable manufacturing, unqualified insulation materials, low insulation performance, aging of DC system insulation, or the presence of certain damage defects can cause grounding or become a grounding hazard. In addition, small animals invading or biting in outdoor environments can also cause DC ground faults. Therefore, in this case, an armored cable with a rodentproof functional sheath is generally used.
Distributed PV common inverter cable selection:
Note: The cable in the form is based on the standard of the national standard copper wire.
If the cable length is greater than 50 meters, please refer to the cable of the larger size.
5. Cable construction of photovoltaic power generation system
The cost of cable engineering construction in photovoltaic power generation projects is generally large, and the choice of laying method directly affects the construction cost. Therefore, rational planning and proper selection of cable laying methods are important links in cable design work.
1. The laying method of cable laying cable is comprehensively considered according to the engineering conditions, environmental conditions, cable specification model, quantity and other factors, and is selected according to the requirements of reliable operation, easy maintenance and technical and economical rationality. The laying of DC cables for photovoltaic power generation projects mainly includes laying of sand buried bricks, laying of pipes, laying of trenches, laying of cable trenches, and laying of tunnels.
The laying of AC cables is not much different from that of general power systems. DC cables are mostly used between photovoltaic modules, between strings to DC combiner boxes, between combiners and inverters. The cross-sectional area is small and large. Generally, cables are bundled along the component brackets or directly buried. DC cables should generally be considered when laying:
(1) The connecting cable between the components and the connecting cable between the string and the combiner box, as far as possible, using the component bracket as the channel support and fixing of the cable laying, can reduce the influence of environmental factors to a certain extent.
(2) The force of cable laying should be uniform and appropriate, and should not be too tight. The temperature difference between day and night in photovoltaic places is large, and cable breakage should be avoided caused by thermal expansion and contraction.
(3) In the photovoltaic material cable lead on the surface of the building, the overall aesthetic appearance of the building should be considered. The laying position should avoid laying cables at the sharp corners of the wall and the bracket to avoid short circuit caused by cutting or grinding damage to the insulation layer, or cut by shearing force. The wire causes an open circuit. At the same time, it is necessary to consider the problem that the cable line is directly struck by lightning.
(4) Reasonably plan the cable laying route, reduce the crossover, and merge as much as possible to reduce the amount of earthwork excavation and cable usage during the construction of the project.
2. Cable connection The DC cable in the photovoltaic power generation system is mostly laid outdoors. The connection method is mainly joint plugging, which can be protected in the pipe, and the component bracket is used as the channel and fixing of the cable laying to reduce the influence of environmental factors. . Other cable connections are roughly the same as in conventional power systems.
A single-phase VFD, also known as a variable frequency drive, is a specialized electronic device used for precise control and regulation of single-phase motors. Unlike three-phase motors that are commonly used in industrial applications, single-phase motors are predominantly found in residential and small-scale applications.
The primary function of a single-phase VFD is to control the frequency and voltage supplied to the single-phase motor, thereby enabling accurate regulation of motor speed. By adjusting the frequency and voltage output, the VFD allows for smooth and precise control over the motor's rotational speed. This feature is particularly useful in applications where speed control is required, such as in residential HVAC systems, small-scale machinery, and household appliances.
Energy efficiency is a significant advantage offered by single-phase VFDs. By adjusting the motor speed to match the load requirements, the VFD reduces energy wastage and improves overall energy efficiency. When the motor operates at a lower speed during periods of low demand, energy consumption is significantly reduced, resulting in energy savings and lower operating costs.
Motor protection is another important aspect addressed by single-phase VFDs. They incorporate various protective features, including overload protection, short circuit detection, and thermal protection, which help safeguard the motor against damage due to excessive current, voltage fluctuations, or overheating. This ensures reliable motor operation, prolongs the motor's lifespan, and reduces the risk of unexpected failures.
Harmonic filtering is also a critical consideration in single-phase VFD applications. When single-phase VFDs operate, they can introduce harmonics into the power supply, which may cause issues such as voltage distortions and interference with other electrical equipment. To mitigate these problems, single-phase VFDs often incorporate harmonic filtering techniques to suppress harmonics and ensure a clean and stable power supply, maintaining power quality and preventing damage to connected equipment.
Control algorithms play a significant role in single-phase VFD operation. These algorithms allow for precise control and adjustment of motor speed, ensuring smooth acceleration, deceleration, and accurate speed regulation. Advanced control algorithms enable efficient motor operation and enhance overall system performance.
In summary, single-phase VFDs provide precise control and regulation of single-phase motors in residential and small-scale applications. With their energy efficiency, motor protection features, harmonic filtering capabilities, and advanced control algorithms, single-phase VFDs enhance motor performance, reduce energy consumption, and ensure reliable operation in various residential and small-scale applications.
Three Phase Vfd,Ac Single Phase Gasoline Generator,220V Vfd,Ac Inverter
WuXi Spread Electrical Co.,LTD , https://www.vfdspread.com