Manual disconnect switches provide safe isolation during maintenance and service, but they are not designed to interrupt current under load, especially in high-voltage DC systems where arcs are difficult to extinguish. This application note explains the physical arcing mechanism that occurs when a manual switch opens under load, the damage and safety risks involved, and why these switches should be used for isolation only. It describes the correct design approach: use purpose-built devices such as contactors or circuit breakers with arc-quenching mechanisms to interrupt high-voltage, high-current circuits. The guidance helps engineers design safe service and isolation procedures and select the right device for load interruption.
