Softstarter for heavy motor loads
The ABB PSTB840 1SFA894019R7020 is a softstarter rated 840 A in-line connection, delivering 450 kW at 400 V and 800 kW in inside-delta configuration. That 840 A continuous rating means it handles large induction motors — pumps, conveyors, compressors — up to that full-load current without external bypass contactors, because the built-in bypass signal relay confirms the unit has transitioned to run mode. The control supply is 100-250 V AC; a separate 24 V DC control circuit is also available for PLC-driven panels.
Built-in protection and ramp control
Integrated electronic overload protection eliminates the need for a separate overload relay — the softstarter itself monitors motor current and trips on overload. Current limit is adjustable from 1.5 to 7 times the set motor current Ie, and the ramp time is settable from 0 to 120 seconds. Initial voltage during start is adjustable 30-70 %, with a step-down voltage special ramp from 100-30 % for soft stopping pumps to prevent water hammer. Starting capacity is 3xIe for 15 seconds, which covers most standard squirrel-cage motor start profiles. The unit includes run, fault, bypass, and overload signal relays — four separate dry contacts for the PLC or DCS to monitor status.