Rated for the motor load, not just the nameplate
The ABB PST60 soft starter 1SFA895006R7020 carries two distinct current ratings that govern how it connects to the motor. In-line connection is rated 60 A — that is the current through the starter when wired directly in the supply lines. Inside-delta connection (switches in the delta legs) is rated 105 A, which lets it start a 55 kW motor at 400 V. The 60 A in-line figure is the one to match against the motor FLA for a standard installation; the 105 A delta figure applies only when the starter is wired per the inside-delta topology, which reduces the current per phase through the thyristors. Main circuit voltage range is 400 to 690 V AC, covering standard European 400 V three-phase and 690 V industrial networks. The control supply is 100-250 V AC, so it accepts a common panel control transformer without a separate DC supply. Built-in electronic overload protection eliminates the need for a separate overload relay in most applications — the starter itself handles thermal protection based on motor current, not just a bimetallic curve.
Ramp and start parameters
Ramp time is adjustable from 0 to 120 seconds, giving a wide window for soft-starting conveyors, pumps, or fans. Initial voltage during start is settable between 30 and 70 % of line voltage, and the step-down voltage special ramp can be set from 100 down to 30 %. Starting capacity is 3xIe for 15 seconds, which handles typical high-inertia loads without nuisance tripping. The current limit function is adjustable from 1.5 to 7 times the set Ie, so you can clamp the inrush to a multiple of the motor FLA.
Signals and integration
The starter provides four signal relays: run, fault, by-pass, and overload. These give the PLC or DCS discrete feedback for each state without needing auxiliary contactors. Analog output is 0-10 V, usable for a panel meter or drive speed reference. Communication is via a standard FieldBusPlug — the starter accepts a fieldbus adapter module, not a built-in protocol stack. Screw terminals on the control circuit with a tightening torque of 0.5 N·m. Main circuit connecting capacity is rigid 1 x 10 to 95 mm², sized for the 60-105 A range.