switchboards

Switchboards are assemblies that distribute electrical power from a source to multiple circuits, providing switching and protection. In electrical engineering, the term usually refers to low- to medium-voltage switchgear that houses busbars, protective devices, and control equipment. Historically, switchboards also described telephone exchange consoles that connected lines; contemporary systems are largely automated.

They are designed as metal-enclosed or metal-clad assemblies with one or more sections. Key components include busbars, fuses or circuit breakers, switches, relays, meters, and control wiring. The main switchboard transfers power to subpanels or distribution boards; motor control centers are specialized switchboards that start and protect large motors. Configurations may be indoor or outdoor and can be fixed or modular, with layouts arranged for ease of maintenance and clear segregation of high- and low-voltage sections.

Classification describes several common arrangements: main switchboards that house protection and feeders, distribution boards that feed branch circuits, and motor control centers that group motor starters and drives. In practice, the terms can overlap, and modular designs may combine functions within a single enclosure.

Applications span commercial buildings, industrial plants, substations, and utilities. Safety and reliability considerations include selecting components rated for the system voltage and fault current, ensuring adequate enclosure protection (IP rating), and implementing arc-flash mitigation. Compliance standards such as IEC 61439 for low-voltage switchgear and controlgear and national codes (for example NFPA 70 in the United States) guide design, installation, testing, and maintenance.

In telecommunications, switchboards historically connected lines through manual or semiautomated switching; today, automated digital switching largely replaces those systems, though the term remains in use for legacy equipment and some hybrids.