Inverter AC Output Parameters and Cable Selection

I. Introduction to AC Copper CsmetsyS ciables for Photovoltaic Systems

• Common Cable Types
  • In photovoltaic systems, BVR and YJV are commonly used AC copper cables. BVR, which stands for copper - core PVC - insulated flexible wires, is known for its flexibility. This makes it suitable for applications where cables need to be bent or routed in tight spaces, such as in some indoor or complex installation environments of photovoltaic systems. For example, when connecting an inverter to a nearby distribution box in a small - scale rooftop solar installation, BVR cables can be easily maneuvered.
  • YJV, on the other hand, refers to cross - linked polyethylene - insulated power cables. Cross - linked polyethylene insulation provides better electrical performance, higher temperature resistance, and greater mechanical strength compared to PVC insulation. YJV cables are often used in more demanding outdoor and long - distance applications in photovoltaic power plants, where they can withstand harsh environmental conditions.
• Selection Considerations
  • When selecting these cables, voltage class and temperature class are crucial factors. The voltage class of the cable must match the output voltage of the inverter to ensure safe and efficient power transmission. For instance, if an inverter has an AC output voltage of 400V, the cable should be rated for at least this voltage level.
  • Temperature class is also important as the cable needs to operate within a specific temperature range without degrading its performance. In a hot climate, a cable with a higher temperature rating should be chosen. Additionally, flame - retardant types are recommended to enhance the safety of the system in case of a fire.

II. Cable Specification Notation

• Single - core Branch Cables
  • The specification of single - core branch cables is denoted as 1 * nominal cross - section. For example, a cable marked as 1 * 25mm 0.6/1kV means it is a single - core cable with a nominal cross - sectional area of 25 square millimeters. The “0.6/1kV” indicates the rated voltage of the cable, where 0.6kV is the phase - to - neutral voltage and 1kV is the phase - to - phase voltage. This type of cable is often used for single - phase circuits or as a branch for a larger electrical system in a photovoltaic setup.
• Multi - core Stranded Branch Cables
  • The specification of multi - core stranded branch cables is expressed as the number of cables in the same circuit * nominal cross - section. For example, a cable marked as 3 * 50 + 2 * 25mm 0.6/1KV is a multi - core cable. It consists of three 50 - square - millimeter live wires, which are used to carry the three - phase power. The “2 * 25mm” represents one 25 - square - millimeter neutral wire and one 25 - square - millimeter ground wire. The neutral wire is used to complete the electrical circuit, and the ground wire provides a safety path for electrical faults.

III. Impact on Inverter AC Output

• Cable Resistance and Power Loss
  • The cross - sectional area of the cable affects its resistance. A cable with a smaller cross - sectional area has higher resistance, which leads to greater power loss during power transmission. For an inverter's AC output, this can result in reduced efficiency. For example, if an undersized cable is used for the inverter's output, a significant amount of power may be lost as heat in the cable, reducing the amount of power that reaches the load or the grid.
• Voltage Drop
  • Cable resistance also causes a voltage drop along the cable length. A large voltage drop can affect the performance of the connected equipment. In a photovoltaic system, if the voltage drop in the AC output cable is too large, the inverter may not be able to operate at its optimal efficiency, and the connected loads may experience unstable voltage supply.

IV. FAQ

• Q: Can I use a cable with a lower voltage class than the inverter's output voltage?
  • A: No, it is not recommended. Using a cable with a lower voltage class can pose a safety risk, such as insulation breakdown and electrical arcing, which can lead to equipment damage and even fire. Always choose a cable with a voltage class equal to or higher than the inverter's output voltage.
• Q: How does cable length affect the selection of cable cross - sectional area?
  • A: As the cable length increases, the resistance of the cable also increases. To minimize power loss and voltage drop, a larger cross - sectional area cable should be used for longer cable runs. For example, in a large - scale photovoltaic power plant where the inverter is far from the grid connection point, a cable with a larger cross - sectional area is required.
• Q: Are there any other factors to consider besides voltage class and temperature class when selecting cables?
  • A: Yes, other factors include the ampacity (current - carrying capacity) of the cable, the environmental conditions (such as humidity, dust, and exposure to chemicals), and the mechanical protection requirements. For example, in a coastal area, a cable with better corrosion resistance should be selected.