Introduction
If your conveyor jerks when it starts, trips breakers on launch, or wears out belts faster than it should, you don’t have a motor problem — you have a starting problem. A properly sized ABB soft starter eliminates that. But “properly sized” is the operative phrase. This guide walks through the selection process, so you spec it right the first time.
Why Use a Soft Starter on a Conveyor?
Conveyors are one of the most common soft starter applications for good reason. Direct-on-line (DOL) starting pulls 6–8x full-load current and slaps the load with full torque instantly. That mechanical shock shortens belt life, stresses couplings, and hammers gearboxes. A soft starter ramps voltage up gradually, controlling torque during acceleration so the conveyor reaches full speed smoothly.
Step 1: Know Your Motor
You need three numbers before you open a catalog:
- Full Load Amperage (FLA) from the motor nameplate
- Voltage — 230V, 460V, or 575V three-phase
- Starting torque requirement — light (empty belt) or heavy (loaded at start)
Step 2: Understand the Load Type
ABB classifies conveyor applications as Class 20 or Class 30 depending on start duration. Most horizontal conveyors are Class 20. Incline conveyors or those that start loaded are Class 30 and require a soft starter rated for heavier duty cycles.
Step 3: Select the ABB PSR or PSTX Series
ABB’s PSR series covers light-duty applications up to 45A. For anything heavier — long conveyors, inclines, or frequent starts — the PSTX series offers electronic bypass, built-in motor protection, and fieldbus communication. The PSTX is the right call for any conveyor running more than 4 starts per hour.
- PSR3…PSR45: Simple voltage ramp, compact panel footprint, light duty
- PSTX18…PSTX1050: Full-featured, bypass contactor built in, motor protection included
Step 4: Don’t Forget Bypass
Once a motor reaches full speed, a soft starter should be bypassed — either internally (PSTX) or with an external bypass contactor. Running a soft starter in-circuit continuously generates heat unnecessarily and shortens SCR life. If you’re using a PSR, add a bypass contactor sized to the motor FLA.
Step 5: Set the Ramp Time
Most conveyor applications run well with a 5–10 second ramp time. Too short and you defeat the purpose; too long and you risk overheating the soft starter. ABB’s PSTX allows ramp time adjustment via the built-in keypad or through a fieldbus connection.
The FES Advantage
Frontier Electric Supply stocks ABB PSR and PSTX soft starters at both our Bensenville, IL and New Carlisle, IN locations. If you’re in Chicagoland or Northwest Indiana, you can have the right unit in your hands today — not next week.
Call FES to spec your ABB soft starter: (630) 595-8730 | (574) 988-0019