Sizing a direct starter for a 370 W motor at 400 V
The 3RA2115-0KA15-1BB4: This SIRIUS 3RA2 non-fused motor starter is a pre-assembled direct starter combining a contactor, thermal overload relay, and magnetic short-circuit trip in one unit — size S00 frame. At 400 V AC-3 duty it's rated for 370 W motor output, and at 690 V AC-3 it handles up to 750 W. The 24 V DC coil matches standard PLC control voltage without an interposing relay. The magnetic short-circuit trip clears faults before the contactor welds, so the upstream feeder breaker doesn't need to coordinate down to the motor locked-rotor current.
Panel fit and clearance envelope
The unit measures 45 mm wide by 167.2 mm high by 97.1 mm deep — size S00 footprint. Mounting is snap-on to 35 mm DIN rail or screw-mount with the additional push-in lug. Vertical mounting position is specified; the clearance requirements are 20 mm upward, 10 mm downward, 9 mm at the sides, and zero forward or backward — so it fits tight against the back panel. AWG equivalents are 2× (20-16) and 2× (18-14) for the contactor side. The supplied link module 3RA1921-1DA00 bridges the contactor to the circuit-breaker — no extra bus bars needed.
Temperature range and storage logistics
Operating ambient is -20 to +60 °C; storage range is -50 to +80 °C; transport range is -55 to +80 °C. The -55 °C transport floor matters for cold-chain shipments — no special heated packaging needed for standard freight. Pollution degree 3 means it's rated for industrial environments with conductive pollution (condensation, light dust).