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    Home > Product > Electric Drive > Soft Starter
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Soft Starter

A motor soft starter is an electrical device designed to temporarily reduce the load and torque in the powertrain and the electric current surge of an AC motor during startup. By gradually increasing the voltage, it enables a smooth start for the motor, protecting it from electrical stress and extending its lifetime. Soft starters optimize starting currents to match the specific load, application, and motor size, and they include over ten motor protection features to safeguard the motor from various load and network irregularities.

VEICHI is one of leading motor soft starter manufacturers in China, our soft starters are widely used in various general-purpose machinery (such as fans and pumps) and heavy-load, fast-response applications (like conveyor belts, compressors, and crushers), reducing long-term operating costs through intelligent energy-saving control.

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More About Soft Starter

What's the difference between a soft starter and a VFD?

1. Working Principle

  • Soft starters gradually increase motor voltage using SCRs, controlling current and torque surges to protect the motor and reduce heating. They can manage one to three phases, with three-phase control being optimal. Bypass contactors are used at maximum speed for further efficiency.
  • VFDs convert DC power to adjustable AC power using inverters, modulating frequency and voltage for precise speed control of AC motors. They offer continuous speed adjustment by varying frequency and voltage, providing dynamic control.

2. Function

  • Soft starters limit motor current and torque during startup to perform soft starts, but does not control speed once the motor is running. Soft starters don't need additional filters. 
  • VFDs control motor speed during operation by varying frequency and voltage, offering dynamic control over speed, torque, and power. VFDs require fillers because of harmonics injection in the line. 

3. Price

Soft starters typically have a lower initial cost, while VFDs require a higher initial investment.

4. Application

  • Soft starters used for constant motor speed application. Ideal for constant torque loads like conveyors and extruders that require gentle ramp-up. Suits applications where speed is fixed after startup.
  • VFDs used for variable motor speed application. Best suited for fixed-speed applications where smooth startups are critical, such as pumps and fans.

When to use a soft starter or VFD?

VEICHI electrical engineers suggest using soft starters when a motor merely requires a starting system, and opting for VFDs when speed control during operation is also needed. A soft starter is incapable of conserving energy by adjusting the speed of a motor with a variable load, and a VFD's speed control capability is underutilized when employed solely as a starter.

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