Which equipment is used to control both voltage and current in electrical systems?

The charge controller is used to manage voltage and current levels, particularly in renewable energy systems like solar power setups. Its primary function is to regulate the charge going to batteries from solar panels by adjusting the voltage and current, ensuring that the batteries are charged efficiently while preventing overcharging and deep discharging, which can damage them.

In contrast, other equipment listed, such as switchboards, primarily facilitate the distribution of electrical power, whereas transformers mainly adjust voltage levels without directly managing current flow. Circuit breakers are safety devices designed to protect electrical circuits from overloads or faults by interrupting the current flow but do not actively regulate voltage or current under normal operating conditions. This makes the charge controller uniquely suited for the function described in the question, as it plays a crucial role in managing both voltage and current levels effectively.