The Siemens 3RK4320-3GQ51-0BA2 is a SIRIUS MCU motor starter, a compact direct-starter design with integrated AS-Interface communication for distributed motor control in automation cells. It is rated 2.5 A at AC-3 400 V, Trip Class 10, meaning it is sized for switching and protecting small three-phase induction motors (up to roughly 0.75 kW at 400 V) under moderate starting duty — the CLASS 10 trip curve clears overloads within 10 seconds at 7.2× rated current, typical for standard conveyor and pump applications. The control supply is 20.4...26.4 V DC, and the operating voltage on the main circuit is 340...440 V at 50/60 Hz.
AS-Interface integration and I/O
This motor starter communicates via AS-Interface protocol (no PROFIBUS DP or PROFINET onboard — the AS-i bus handles the control and feedback). It provides 2 digital inputs for local sensors or limit switches, and includes a motor brake output as a product component.
Protection and environment
Motor protection is bimetal-based (thermal overload), with short-circuit protection handled by an upstream circuit-breaker (not integrated). The enclosure is rated IP54, so it is suitable for installation in control cabinets where dust and splash ingress is expected, but not for washdown zones.