What are the usage scenarios of DC combiner boxes?

The operating principle of a combiner box primarily involves circuit connection and protection. When photovoltaic modules generate DC power, they are connected to the combiner box's input port via cables. The circuitry within the combiner box combines and distributes this DC power, then outputs the combined DC power to an inverter or other equipment. During the combining process, the combiner box monitors parameters such as current, voltage, and power for each photovoltaic string, and implements protection devices for short circuit, reverse connection, and overcurrent.

1. DC combiner box

This combines multiple DC currents generated by a solar array to the inverter's input. To reduce impact on the grid and prevent damage to the inverter due to excessive voltage, a multi-channel parallel connection is typically used. Based on the inverter's input DC voltage range, a certain number of PV modules of the same specifications are connected in series to form a PV module string. These strings are then connected to the PV array lightning protection combiner box. The output is then routed through a lightning arrester and circuit breaker, facilitating connection to subsequent inverters.

2. AC combiner box

It is used for photovoltaic power generation systems composed of string inverters and is installed between the AC output side of the inverter and the grid connection point/load. It is equipped with input circuit breakers, output circuit breakers, AC lightning arresters, and optional intelligent monitoring instruments (monitoring system voltage, current, power, electric energy and other signals). Its main function is to combine the output currents of multiple inverters and protect the inverters from harm from the AC grid connection side/load. It serves as the disconnect point of the inverter output, improves the safety of the system, and protects the safety of installation and maintenance personnel.

Notes on electrical installation of combiner box

(1) Only professional electrical engineers can operate and connect the wires; the operation and wiring must comply with the relevant standards of the country and the local area;

(2) Before installing the combiner box, use a megohmmeter to perform insulation testing on the internal components.

(3) The layout and spacing of the components in the box should comply with the provisions of relevant regulations and should ensure the requirements of commissioning, operation, maintenance, inspection and safe operation.

(4) The input and output cannot be connected in reverse. 

(5) After connecting the PV lightning protection junction box to the PV power generation system, the grounding terminal of the lightning protection box should be reliably connected to the lightning protection ground wire or busbar.

(6) When connecting external wiring, ensure that the screws are tightened to prevent the wiring from loosening.

(7) A non-fading system diagram and necessary secondary wiring diagrams should be firmly affixed inside the box or on the cabinet door.

(8) Flame-retardant cables should be used for wiring. They should be arranged neatly, beautifully, and securely installed to ensure good contact.