Motor current and service factor
Select against the motor nameplate current and the manufacturer’s application table, including any ambient or enclosure derating.
Reduced-voltage motor starting
Soft Starters for Controlled Motor Acceleration
Reduce mechanical shock and starting current when variable-speed operation is not required. We help match soft starters to motor current, starts per hour, acceleration time, load torque and bypass requirements.
- Low- and medium-voltage starting options
- Application and start-duty review
- Current-model replacement support
Selection foundation
Choose a soft starter from the complete start profile.
A soft starter controls voltage during acceleration and deceleration but does not regulate motor speed during normal running. Selection therefore focuses on motor full-load current, load torque, required start time, starts per hour and thermal duty. Pumps may benefit from controlled stopping to reduce water hammer, while high-inertia loads can require more current capacity or a different starting method.
Start severity
Start time, initial torque, current limit, starts per hour and load inertia determine the thermal demand placed on the starter.
Internal or external bypass
A bypass contactor reduces heat after acceleration. Confirm whether it is built in, separately supplied or controlled by the starter.
Protection and control
Review motor overload functions, phase protection, current monitoring, fieldbus options and the required start/stop interface.
Product range
Product types within this category
These groups are a practical way to narrow the requirement. Final model selection still depends on the electrical, mechanical and installation data shown on this page.
Compact soft starters
Simple reduced-voltage starting for smaller motors with a focused control set and space-efficient installation.
Typical fit: Basic pumps, fans and light-duty machinery
Internal-bypass soft starters
Integrated bypass contactors reduce enclosure wiring and heat after the motor has completed acceleration.
Typical fit: Standard industrial starts with defined duty
External-bypass soft starters
Starter and bypass components are coordinated separately when the project standard, service strategy or current rating requires it.
Typical fit: Custom panels and project-specific protection schemes
Pump-control soft starters
Models with starting and stopping functions intended to improve pressure transitions in suitable pumping systems.
Typical fit: Water transfer, booster and process pumps
Heavy-duty soft starters
Higher thermal capacity and advanced control selected for long acceleration, frequent starts or difficult torque profiles.
Typical fit: Loaded conveyors, crushers and high-inertia equipment
Medium-voltage soft starters
Engineered systems for large motors where switching, insulation, protection and site coordination require a project review.
Typical fit: Large pumps, compressors, fans and mills
Quick selection
Start a soft-starter selection
Select any available data. If the start duty is unknown, send the motor label and describe the driven equipment in WhatsApp.
Typical specification scope
What we can match
- Selection basis
- Motor current plus start duty
- Voltage classes
- Common low-voltage and selected MV systems
- Starting methods
- Voltage ramp, current limit and torque control by model
- Stopping functions
- Coast, soft stop and pump control by model
- Bypass
- Internal or external contactor arrangements
- Supply formats
- Starter, accessories or complete panel
Common applications
Where selection changes with the load
Centrifugal pumps
Controlled acceleration and pump-stop functions can limit pressure transients and mechanical stress in suitable systems.
Fans and blowers
A soft starter can reduce inrush and belt stress when continuous speed control and energy optimization are not needed.
Conveyors
The required breakaway torque, loaded start and acceleration time must be checked carefully before choosing the starter rating.
Compressors and high-inertia loads
Unloaded-start arrangements, current limits and thermal capacity are reviewed to confirm whether a soft starter is appropriate.
Decision guide
Choose the right product path before comparing models
Soft starter
- Choose when
- The motor runs at full speed after starting and the goal is reduced inrush or mechanical shock.
- Verify before ordering
- Start torque, current limit, acceleration time, starts per hour and stopping need.
Variable frequency drive
- Choose when
- Operating speed must vary or the process benefits from continuous speed and torque control.
- Verify before ordering
- Speed range, energy profile, motor cooling, harmonics and control method.
Across-the-line starter
- Choose when
- The supply and machine can accept full starting current and mechanical acceleration.
- Verify before ordering
- Utility limits, voltage dip, motor protection and driven-equipment stress.
Star-delta or autotransformer start
- Choose when
- A conventional reduced-voltage method is required by an existing standard or installed system.
- Verify before ordering
- Motor connections, transition torque, switching current and available panel space.
From requirement to quotation
A short path to a verifiable product match
Send motor and load data
Provide motor current and voltage, starts per hour, start time and a short description of the driven equipment.
Check starting duty
The required current, torque, bypass, protection and control functions are compared with manufacturer selection data.
Confirm model and accessories
The quotation identifies the starter rating, bypass basis, optional communication and any panel components included.
Frequently asked questions
Practical answers before you request a quote
What is the difference between a soft starter and a VFD?
A soft starter mainly controls acceleration and stopping, then the motor runs at line frequency. A VFD controls motor speed during operation. Use a VFD when process speed control or substantial variable-speed energy savings are required.
Can a soft starter reduce pump water hammer?
Some models include pump-control algorithms intended to improve starting and stopping transients. The result depends on the hydraulic system, so valve behavior, pipework and operating sequence still need engineering review.
Can the soft starter rating equal the motor current?
Sometimes, but only when the manufacturer’s duty table covers the application, start time, starts per hour and ambient conditions. Heavy or frequent starts can require a larger starter.
Does a soft starter need a bypass contactor?
Many starters use an internal or external bypass to reduce heat after the motor reaches speed. Confirm the model’s design and ensure that protection and control remain correct during bypass operation.