Siemens SIRIUS soft starter: 3RW30, 3RW40 or 3RW44 for your motor
Customers buy Siemens from us in two camps. First: plants that already run other Siemens automation (S7-1200/1500, ET 200, Sinamics drives) and need to keep one ecosystem through TIA Portal. Second: those who buy SIRIUS specifically because the cabinet already has a Siemens 3RT contactor and the wiring logic must stay. We stock three series: 3RW30 (up to 55 kW), 3RW40 (up to 250 kW), and 3RW44 (top, up to 710 kW). This year's typical customer: a plant modernization engineer whose old magnetic contactor keeps burning out from heavy mixer starts.
How to choose between the series. We ship 3RW30 when you need a cheap reliable compact for a fan; a low-kW pump; a belt conveyor without frequent starts. No fieldbus, just a relay output; setup via DIP switches in 5 minutes. We ship 3RW40 when you need serious motor protection (overload, imbalance, rotor lock) plus adjustable ramp-up/stop times; it has RS-485 for basic SCADA. We ship 3RW44 when the load is heavy (crusher; ball mill; piston compressor) or when you need Profibus DP / Profinet for full TIA Portal integration. 3RW44 has built-in bypass, so the panel runs cooler plus takes less space.
What we ask before the order
First: motor FLA from the nameplate plus power. Not the spec sheet, the actual nameplate, because real values drift by 5-15%. Second: what automation you already run. If it is TIA Portal with ET 200, we go straight to 3RW44 with Profinet, because reworking other series later costs more. Third: starts per hour (3RW30 likes rare; 3RW44 handles up to 6 per hour at S4 50%). Fourth: panel temperature, because above 40°C you need to derate.
This year's best-sellers from our warehouse for typical jobs: 3RW3016-1BB14 (9 A, 4 kW, domestic plus small pumps); the 3RW30 series for boiler rooms plus ventilation units; 3RW40 at 75-110 kW for compressors plus conveyors. Siemens warranty 24 months. 3RW30/3RW40 ship from our Kyiv warehouse in 1-3 days, some 3RW44 frame sizes ship to order (5-15 days). Datasheet available before payment, plus we walk you through parameter setup via the A button.
