AS-Interface reversing starter with CLASS 10 bimetal protection
The Siemens 3RK4320-3AQ51-1BA3 is a SIRIUS reversing motor starter designed for AS-Interface bus communication — it switches and protects a motor in both directions without a separate reversing contactor pair.
Bus integration and control supply
AS-Interface protocol is supported natively, so the starter connects directly to the AS-i yellow cable — no separate gateway module for the motor branch. The control supply is 20.4–26.4 V DC, drawn from the AS-Interface power supply unit. Two digital inputs are available on the unit for local pushbuttons or limit switches, reducing the need for a separate I/O block at the motor.
Mounting, enclosure, and environmental limits
IP54 protection suits installation in control cabinets or enclosed machine cells where occasional dust and splash ingress may occur. Dimensions are 245 mm wide, 215 mm high, 205 mm deep.
Motor brake output and short-circuit protection
The unit includes a motor brake output controllable with 400 V AC — for applications like conveyors or hoists that need a holding brake, the starter supplies the brake coil directly. Short-circuit protection is provided via circuit-breakers; the starter itself is not a stand-alone SC protection device, so an upstream breaker sized to the branch is required.