Softstarter for heavy motor starts
The ABB PSTB840 (1SFA894019R7000) is a softstarter rated for 840 A in-line connection, delivering 450 kW at 400 V — sized for large induction motors driving pumps, conveyors, or compressors in industrial plants. The 208-600 V AC main circuit voltage range covers standard low-voltage networks globally. Built-in electronic overload protection eliminates the need for a separate overload relay, saving panel space and wiring. The current limit function is adjustable from 1.5 to 7 times the rated current, giving flexibility for different starting torque requirements. Ramp time is configurable from 0 to 120 seconds, allowing a smooth acceleration profile matched to the load. Initial voltage during start can be set between 30% and 70% of line voltage, with a step-down voltage special ramp from 100% down to 30% for soft stopping.
Control and communication
Control supply voltage is 100-250 V AC; a separate 24 V DC control circuit voltage is also available for logic-level interfacing. The unit includes run, fault, by-pass, and overload signal relays, plus a red fault LED and yellow protection LED for local status indication. Communication is via a standard FieldBusPlug, allowing direct connection to a fieldbus network without additional gateway hardware. Analog output provides 0-10 V for speed or current feedback to a PLC or drive controller. Main circuit terminals are bars with a 12.5 mm hole diameter for bolted connections; control circuit terminals accept rigid 1 x 2.5 mm² wire with a tightening torque of 0.5 N·m. The inside-delta connection option enables higher starting capacity — 1455 A and 800 kW at 400 V — for demanding applications.