Siemens Q390 Industrial Three-Phase Plug-In Circuit Breaker

Siemens Q390 is a 3-pole, 90A plug-in circuit breaker in the QP line, engineered for 240V AC distribution in light- to heavy-duty industrial and commercial panels. As a molded case circuit breaker with thermal-magnetic operation, it provides overload protection and short-circuit interruption with a common-trip across all three poles, helping ensure simultaneous disconnection on a fault. The device is designed for plug-in mounting in compatible Siemens enclosures and follows a full-module footprint of 1 inch per pole, facilitating dense, modular panel layouts. The Q390 is rated for up to 10 kA interrupting capacity at 240V, and it is UL-listed for use in 3-phase grounded systems, aligning with typical building and equipment protection standards. Common applications include protecting 3-phase motors, conveyors, compressors, and other industrial equipment fed from 240V circuits, as well as serving as a reliable main or branch protection device in control panels and distribution panels where a compact, plug-in 3P solution is required.