Detailed Explanation of Photovoltaic AC Combiner Box for Photovoltaic Power Station
1. Preface
For a huge photovoltaic power station, the amount of the combiner box only accounts for 1%, but 100% of the current passes through it. During commissioning, operation and maintenance, combiner box failures account for 20-30% of the entire power station. In addition, an unsafe combiner box is very likely to cause a fire and threaten property and personal safety.
Next, we will introduce the photovoltaic AC combiner box from aspects such as product function introduction, product display, technical parameters, wiring schematic diagram, installation tools, installation precautions, and wiring, aiming to let photovoltaic people understand the combiner box better and understand its installation methods and details to pay attention to.
2. Product Function Introduction of Photovoltaic AC Combiner Box
- The photovoltaic AC combiner box is used in a photovoltaic power generation system with string inverters and is installed between the AC output side of the inverter and the grid connection point/load.
- It is internally equipped with input circuit breakers, output circuit breakers, and AC lightning arresters. Optional intelligent monitoring instruments (monitoring system voltage, current, power, electrical energy and other signals).
- Main functions: Combine the output currents of multiple inverters, and at the same time protect the inverters from being harmed by the AC grid-connected side/load. As the disconnection point of the inverter output, improve the safety of the system and protect the safety of installation and maintenance personnel.
3. Product Display of Photovoltaic Combiner Box
Taking the AC combiner box with 4 in 1 (400V/50KW) as an example, there are a total of 4 inverters of 50KW:
4. Technical Parameters of Photovoltaic AC Combiner Box
Technical parameters of AC combiner box
Wiring schematic diagram of photovoltaic AC combiner box
5. Introduction to Installation Tools for Photovoltaic AC Combiner Box
Precautions for Installing Photovoltaic AC Combiner Box
- The installation location of the combiner box should fully consider its external dimensions and weight (see the parameter section).
- The installation ambient temperature of the combiner box should be between -25℃ and +60℃, and the relative humidity should be between 0 and 95%.
- The combiner box should be installed in a dry, well-ventilated and dust-proof place.
- Incoming and outgoing line type and installation method: Armored cable enters and exits from the bottom. It is installed by hanging on the rear column of the outdoor photovoltaic module support.
- lAvoid installing in a place directly exposed to the sun. Otherwise, excessive temperature will reduce the power generation of the system and may also affect the service life of the combiner box.
- lIn order to better dissipate heat and facilitate daily maintenance, keep sufficient space in all four directions of the installation of the combiner box.
Note: Torque requirements for circuit connection (current-carrying) screws:
6. Wiring of Photovoltaic AC Combiner Box
Preparation before wiring
- Open the combiner box.
- Put all molded case circuit breakers MCCB in the tripped state.
Input wiring
- Tighten the tightening nut of the incoming cable connector.
Output wiring (recommended)
Tools: crimping pliers; long-handled Phillips screwdriver; M10 hexagon socket wrench (M6).
- The output terminal connection method of the combiner box is similar to the input connection method. Strip the cable and put the copper lug on the stripped wire（Figure 1）.
- Use a crimping tool to crimp the wire（Figure 2）.
- Put on the corresponding heat shrinkable tube. The positive pole is red and the negative pole is black.
- Loosen the waterproof connector and rotate it counterclockwise. Pass the wire through the cable connector.
- Connect the prepared wire to the copper bar at the output end of the circuit breaker. Tighten the M10 screw (torque 25N.m) at the output end and then straighten and flatten the wire.
- Tighten the waterproof connector clockwise.
Figure 1
Figure 2
7. Summary
The photovoltaic AC combiner box is an important component of the photovoltaic system. This article introduces the combiner box from multiple aspects. When choosing equipment, everyone needs to select from multiple aspects such as materials, design, process, testing, and certification, so as to reduce equipment failures, reduce operation and maintenance costs, and increase the safety of photovoltaic systems. Through this sharing, I hope everyone has some understanding of the photovoltaic AC combiner box.