BreakbeforeMake

Breakbeforemake, often written break-before-make, is a switching characteristic in which a contact opens to break an existing connection before a new one is established. In other words, there is a deliberate interval during which no circuit is connected to the common node. This sequencing prevents the old and new contacts from being closed at the same time, reducing or eliminating the chance of shorting or cross-conduction between circuits.

This behavior is commonly contrasted with make-before-break (MBM), where the new connection is established before the old one is released. Breakbeforemake trades continuous connectivity for better isolation and safer transitions, making it suitable for applications where a brief interruption is acceptable or where simultaneous connections could cause faults, arcing, or undesirable current paths.

Applications of breakbeforemake include multi-pole switchgear, relays used to switch power or high-voltage circuits, and instrumentation or control systems where safe isolation between configurations is important. It is often chosen in environments with inductive loads, where overlap could create transients or short circuits, or where systems rely on clear isolation during transition.

Design considerations for achieving breakbeforemake involve contact geometry and sequencing, mechanical travel, and cam or spring timing that ensures the old contact opens before the new one closes. Trade-offs include a potential brief interruption of the connected circuit, which may be undesirable in some applications and acceptable in others.