The ABB 1SFA899301R2250 is a PSBP-1250 bypass contactor designed for use with PSTX series softstarters. Its job is to short-circuit the softstarter's power semiconductors after the motor reaches full speed, transferring the load current to a low-loss mechanical path — standard practice for any softstarter installation above a few kilowatts where continuous conduction through the thyristors would waste energy and generate heat.
What It Fits — PSTX Softstarter Family
The PSBP-1250 mates to the PSTX range of softstarters. In a panel, the bypass contactor sits between the softstarter output and the motor, wired so that when the softstarter signals full-speed, the contactor closes and the thyristors are gated off. The PSBP-1250 designation points to a specific current rating within the bypass family; the same mechanical footprint and coil voltage should be verified against the PSTX frame it pairs with.