Application note
AN0010Using a Manual Switch to Open a Load
Why manual disconnects are for isolation only, and what happens when you try to open one under load.
Summary
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.
