Photovoltaic AC combiner box system

A photovoltaic AC combiner box aggregates the AC outputs from multiple inverters, providing protection, disconnection, and monitoring before the power is fed to the grid or load.

Function and Purpose

A photovoltaic AC combiner box is installed between the AC output of string inverters and the grid connection or load in a solar PV system. Its main functions are to: Combine AC outputs from multiple inverters into a single circuit for easier connection to the grid or distribution panel. Protect inverters and wiring using input and output circuit breakers, preventing damage from overcurrent or faults.

Provide a safe disconnection point for maintenance, enhancing personnel safety during installation or service. Include surge protection to guard against voltage spikes from lightning or grid disturbances.

Components

Typical A

C combiner boxes contain: Input circuit breakers for each inverter to isolate individual units. Output circuit breakers to protect the combined AC circuit.

A

C lightning arresters for surge protection. Optional monitoring instruments to track voltage, current, power, and energy, enabling proactive maintenance and system diagnostics. Busbars and copper connections sized according to the total current of combined inverters.

Example

For a system with four 50 kW inverters, each inverter's AC output connects to a 100 A circuit breaker. The combined output is routed through a 350 A molded case circuit breaker via a copper busbar, ensuring safe and organized distribution. Differences from DC Combiner BoxesWhile DC combiner boxes collect and protect the DC output from multiple solar panel strings before the inverter, AC combiner boxes handle the AC output after inversion.

D

C arcs do not self-extinguish, so DC boxes require specialized fuses and isolators, whereas AC boxes focus on breaker protection and grid safety.

Benefits

Simplifies wiring and reduces the number of cables running to the grid connection. Enhances system safety and reliability. Facilitates monitoring and maintenance.

Provides a centralized point for surge and overcurrent protection. In summary, photovoltaic AC combiner boxes are essential for safely aggregating inverter outputs, protecting equipment, and enabling efficient grid connection in multi-inverter solar PV systems.