The ABB PSTB570 soft starter (1SFA895017R7020) is a 570 A in-line, 987 A inside-delta motor starter with a built-in electronic overload protection relay. Rated operational power reaches 315 kW at 400 V in-line and 540 kW at 400 V inside-delta, making it suitable for medium-to-large induction motors on pumps, fans, compressors, and conveyors in industrial panels.
The inside-delta configuration boosts that to 987 A / 540 kW by placing the starter in the motor's delta windings, reducing current through the power electronics. Both figures are at 50/60 Hz, 400–690 V AC main circuit voltage. Built-in electronic overload protection eliminates the need for a separate thermal relay. The current limit function is adjustable from 1.5 to 7× Ie, and starting capacity is 3× Ie for 15 seconds — enough for most standard-duty motor starts without external bypass contactors. Ramp time spans 0 to 120 seconds, with initial voltage during start adjustable from 30 to 70 %. A step-down voltage special ramp (100 to 30 %) handles pump deceleration to prevent water hammer. The 0–10 V analog output provides a speed or current signal to a PLC or drive controller.
Control and integration
Control supply voltage is 100–250 V AC; a separate 24 V DC control circuit is also available. Communication is via a standard FieldBusPlug — no external gateway needed for PROFIBUS, DeviceNet, or CANopen depending on the plug fitted. Main circuit terminals are bars (hole diameter 12.5 mm); control circuit terminals accept 1 × 2.5 mm² rigid wire at 0.5 N·m torque. Three signal relays are built in: run, fault, and bypass. A separate overload signal relay and a red fault LED plus yellow protection LED provide local status. The inside-delta connection switch is integrated, saving external wiring.