Best Soft Starter Brands for Industrial Motors Ranked
What's the best soft starter brand for industrial motors? Across IEC 60947-4-2 rated ranges, ABB (PSTX), Schneider Electric (Altistart ATS480), and Siemens (SIRIUS 3RW55) rank ahead on closed-loop torque control, built-in bypass design, and long-term spares availability, while Chint and LS Electric compete mainly on price at the voltage-ramp end of the market. Picking the wrong tier means either paying for torque control a simple fan never needs, or under-protecting a pump start that needed it from day one. This ranking works through control-method depth, bypass design, protection functions, fieldbus support, and where each brand draws the line between its economy, mid, and flagship families — PSR/PSE/PSTX, ATS01/ATS22/ATS480, and 3RW50/3RW52/3RW55.
How This Ranking Works
Rank order here is not a popularity list. It is built on four things a panel builder or plant engineer actually pays for: torque control quality (closed-loop vs open-loop voltage ramp), whether the bypass contactor is built in or a bolt-on afterthought, the depth of motor protection functions on board, and how easy the model is to get parts and support for ten years out. Price sits last on purpose — a cheap starter that trips nuisance faults every startup, or that a distributor stops stocking in six years, costs more than the sticker suggests.
On those four criteria, ABB, Schneider Electric, and Siemens sit ahead of the field. Chint and LS Electric are not bad starters; they are a different starter for a different job, not a lesser one.
#1 — ABB PSTX: The Torque-Control and Fieldbus Reference
ABB's soft starter line splits into three tiers. PSR is the compact economy unit — voltage ramp only, no built-in bypass, sized for small motors up to roughly 30 A / 15 kW at 400 V, set with analog trimmers rather than a display. PSE sits in the middle: voltage ramp plus current limit, built-in bypass, no keypad HMI, covering a few hundred amps. PSTX is the flagship, and it is the reason ABB ranks first here.
PSTX runs closed-loop torque control, not just current limit — the starter measures actual motor torque and adjusts firing angle in real time to hold a linear speed rise. It has a built-in bypass contactor, a detachable keypad HMI for on-site commissioning, full motor protection (overload, phase loss, stall, shorted-SCR detection), and native Modbus RTU with an optional Anybus module for Profibus, Profinet, or EtherCAT. Ratings run up to roughly 1250 A, with PSTB extending the range further. PSTX supersedes the older PST/PSTB generation still found on legacy panels.
What we see in the field: panel builders standardize on PSTX for pump and conveyor jobs specifically because the torque-control loop handles load variation without a re-commission, where a voltage-ramp-only unit needs its ramp time re-tuned every time the load changes.
#2 — Schneider Electric Altistart ATS480: The Panel-Standardization Choice
Schneider's range also has three steps. ATS01 is the compact economy unit — voltage ramp, basic torque/asymmetric control, aimed at small motors. ATS22 is the standard workhorse: voltage and torque control, built-in bypass on most references, covering up to roughly 590 A, with a simpler setup procedure than the flagship. ATS480 is the current top of the range and replaces the older ATS48 line directly — same footprint logic, drop-in migration path for panels being refreshed.
ATS480 runs Schneider's Torque Control System (TCS), a closed-loop scheme comparable in intent to PSTX's torque control, with a built-in bypass, graphic display, embedded Modbus, thermal protection modeling for both motor and starter, and dedicated pump/conveyor start profiles. Ratings extend to roughly the 1200 A class. Where ATS480 wins on the shop floor is standardization: a plant already running Altivar drives and Modicon PLCs keeps one HMI language, one comms protocol, and one spares list across the whole panel, which is a real maintenance-cost argument even when PSTX and ATS480 are functionally close.
#3 — Siemens SIRIUS 3RW55: Best Fit for PROFINET-Heavy Plants
Siemens structures its 3RW5 generation the same way. 3RW50 is the economy/standard model — voltage ramp plus current limit, built-in bypass, no torque control. 3RW52 (marketed as "Failsafe") sits mid-range with added safety features and the same bypass design. 3RW55, the "High Feature" flagship, adds closed-loop torque control, an HMI display, adjustable pump ramp profiles, and full motor protection, with ratings up to roughly the 1200 A class. Older 3RW30/3RW40/3RW44 units are still common in the field — 3RW30 is the compact predecessor, 3RW44 was the high-end line before 3RW55 took over.
3RW55's case for the top three rests on one thing: native PROFINET and PROFIBUS support in a plant already built on Siemens TIA Portal and SIMATIC controllers. If the rest of the line is Siemens, 3RW55 removes a gateway device from the panel and keeps diagnostics inside one engineering environment. Outside a Siemens-standardized plant, that advantage narrows to parity with PSTX and ATS480.
Where Chint and LS Electric Fit
Chint and LS Electric compete at the lower end of the price curve, and for the right application that is a legitimate reason to buy one. Their entry models are typically voltage-ramp only — no torque control, bypass often optional rather than built in — which matches a simple fan, small pump, or conveyor with a light, steady load and no fluid-hammer or high-inertia concern. Where they fall short is exactly where torque control earns its keep: high-inertia loads, pumps prone to check-valve slam, or any application running near the sizing limit, where an open-loop ramp cannot correct for load variation the way a closed-loop unit does.
This depends on the application more than the badge. A Chint unit on a light exhaust fan running eight hours a day is a sound spec. The same unit on a large centrifugal pump with a long discharge line is where the savings disappear the first time the check valve slams and the pipe support gets re-engineered.
Head-to-Head: Flagship Torque-Control Models
The real competition is at the top of each range, since that is where torque control, built-in bypass, and fieldbus depth converge. A closer breakdown of these three specifically lives in the ABB PSTX vs Schneider ATS480 vs Siemens 3RW55 comparison; the summary version:
| Criteria | ABB PSTX | Schneider ATS480 | Siemens 3RW55 |
|---|---|---|---|
| Control method | Closed-loop torque control | Torque Control System (TCS), closed loop | Closed-loop torque control |
| Built-in bypass | Yes | Yes | Yes |
| Max rating class | ~1250 A (PSTB extends further) | ~1200 A class | ~1200 A class |
| Native fieldbus | Modbus RTU; Anybus option for Profibus/Profinet/EtherCAT | Embedded Modbus | PROFINET/PROFIBUS native |
| Legacy line replaced | PST/PSTB | ATS48 | 3RW44 |
| Strongest fit | Mixed-vendor plants, protection depth | Schneider/Modicon-standardized panels | Siemens/TIA-standardized panels |
Choosing Between the Three (and When Not To)
If the plant is not standardized on one vendor, ABB PSTX takes a slight edge for protection depth and fieldbus flexibility across mixed-vendor sites. If the panel is already built around Modicon PLCs and Altivar drives, ATS480 keeps the spares list and HMI language consistent. If the site runs TIA Portal and SIMATIC controllers end to end, 3RW55's native PROFINET support removes a gateway device most other combinations need. None of that overrides the sizing check below, and none of it applies if the application is a light-duty fan or small pump where a PSE, ATS22, or 3RW50 — or a Chint/LS Electric unit — does the job for less.
Bypass design deserves a separate look before final selection, since it drives enclosure size and derating more than most spec sheets show; see the dedicated bypass contactor explanation for how that trade-off plays out. For control-method basics, the voltage ramp vs current ramp vs torque control breakdown covers why torque control is the differentiator that separates flagship models from their own economy siblings.
Sizing Beats Brand: Check This Before You Rank Anything
None of the above matters if the unit is sized wrong. Starting torque falls with the square of applied voltage, and this is the trap that catches more soft starter selections than any brand choice.
Formula: Torque vs Voltage Ratio — Source: motor starting theory, applied per IEC 60947-4-2 sizing practice
T / TDOL = (V / Vline)2
| Symbol | Description | Unit |
|---|---|---|
| T | Motor torque at reduced voltage | N·m (or % of DOL) |
| TDOL | Motor locked-rotor torque at full line voltage (direct-on-line) | N·m |
| V | Motor terminal voltage during soft start ramp | V |
| Vline | Full rated line voltage | V |
At 50% voltage, a motor delivers roughly 25% of its DOL locked-rotor torque — not half. If the load's breakaway torque exceeds what the motor produces at the pedestal voltage the starter is set to, the shaft will not turn, no matter which of the three flagship brands is bolted to the panel. This is why sizing the soft starter to the motor and load comes before comparing feature lists, and why high-inertia loads sometimes still need a DOL start or a VFD instead — see the existing soft starter vs VFD comparison for that boundary.
Pump applications carry their own selection logic beyond brand — ramp-down profile and dry-run protection matter as much as starting torque. That is covered separately in the soft starter for pumps guide. For a full walkthrough of every decision point before a purchase, the soft starter selection guide ties sizing, control method, and brand tier together in one place. Stoklink stocks the soft starters discussed here across all three flagship lines plus the economy tiers.
Frequently Asked Questions
Is ABB PSTX better than Schneider ATS480 or Siemens 3RW55?
Not universally. All three run closed-loop torque control, built-in bypass, and comparable protection depth. PSTX has a slight edge in mixed-vendor fieldbus flexibility (Anybus modules cover Profibus, Profinet, and EtherCAT from one platform); ATS480 and 3RW55 win when the rest of the panel is already standardized on their respective vendor's PLC and drive line.
Are Chint or LS Electric soft starters worth buying?
For light-duty fans, small pumps, or conveyors with steady, low-inertia loads, yes — they cost less and the application never needs torque control. For high-inertia loads or pumps prone to check-valve slam, the missing closed-loop control and often-optional bypass make them the wrong tier regardless of price.
Do I need torque control, or is voltage ramp enough?
Voltage ramp (open loop) is enough for loads with low, steady breakaway torque — most fans and small pumps. Torque control earns its cost on pumps (eliminating fluid hammer with a linear speed rise) and high-inertia loads where a fixed voltage profile cannot correct for load variation during the ramp.
What happens if I undersize a soft starter's torque for the load?
Starting torque falls with the square of voltage, so at 50% voltage the motor produces roughly 25% of its DOL locked-rotor torque. If that reduced torque is below the load's breakaway torque, the motor stalls partway through the ramp instead of reaching full speed — the single most common soft starter sizing failure.
Can I replace an older ABB PST, Schneider ATS48, or Siemens 3RW44 with the current model?
Generally yes. PSTX supersedes PST/PSTB, ATS480 replaces ATS48, and 3RW55 supersedes 3RW44 as each vendor's current flagship, typically with a comparable footprint intended for drop-in panel refreshes, though wiring and terminal layout should be checked against the specific legacy model.
Does built-in bypass matter when comparing brands?
Yes — all three flagship models (PSTX, ATS480, 3RW55) include it, which is part of why they rank above economy-tier units. A built-in bypass contactor shorts out the SCRs once the motor is at speed, cutting heat dissipation and enclosure size versus a starter running current through the SCRs continuously.
Conclusion
ABB PSTX, Schneider Altistart ATS480, and Siemens SIRIUS 3RW55 rank ahead of the field on torque control, built-in bypass, protection depth, and spares longevity — Chint and LS Electric compete on price at the economy end, which is the right trade for light, steady loads. Panel standardization usually breaks the tie between the top three more than any spec-sheet difference does. None of that replaces a torque-vs-load sizing check: get that wrong and the brand on the nameplate stops mattering.
