A Soft Starter is designed to limit the mechanical and electrical stresses on electric motors during startup. It works by gradually ramping up the motor’s voltage, which helps reduce the surge of current that occurs when a motor starts suddenly. This process minimizes damage to the motor, connected equipment, and the power distribution system. Soft starters are particularly important in systems where large motors are frequently started and stopped, such as HVAC systems, conveyor belts, and pumps.

Key Functions of Soft Starters:

1. Ramp-up of Voltage: Soft starters control the voltage supplied to the motor, starting at a low voltage and gradually increasing it until the motor reaches its full speed.
2. Current Limiting: By controlling the voltage, soft starters limit the inrush current, preventing excessive power consumption and voltage dips.
3. Overload Protection: Many soft starters include built-in protections for motor overloads, short circuits, and phase failure.
4. Adjustable Settings: Soft starters typically allow users to adjust the acceleration and deceleration rates, offering flexibility for different applications.

Benefits:

• Reduced Mechanical Stress: Smooth startup avoids abrupt mechanical shocks to the motor and connected systems (e.g., pumps or conveyors).
• Energy Efficiency: By reducing the high inrush current, soft starters lower the overall power demand during startup.
• Reduced Maintenance Costs: Less stress on motors leads to longer operational lifespans and fewer breakdowns.
• Cost Savings: They can save on power-related penalties by limiting high inrush currents, and some models even include energy-saving features.

Common Applications:

• Pumps: Prevent cavitation and pipe bursts by ensuring a smooth startup.
• Fans: Smooth motor acceleration avoids high torque and minimizes vibration.
• Conveyor Belts: Reduces wear on the belt and motor during frequent starts and stops.
• Compressors: Prevents overloading the electrical system and reduces motor wear.

Main Brands and Models:

1. Siemens

   • Sirius 3RW30/40/50: These models provide excellent motor protection and are highly customizable for different motor sizes and applications. They are equipped with advanced communication options and diagnostic features.
   • Sirius 3RW44: Compact soft starters that offer simple, efficient protection and are easy to install.

2. Schneider Electric

   • ATS48: These soft starters provide advanced features for large motors, offering smooth acceleration and deceleration, customizable settings, and protection features for motor and load.
   • Altistart 22: A more basic model, suitable for smaller motors, with essential functions such as current limiting and motor protection.

3. ABB

   • PSTX: ABB’s PSTX series is a versatile, easy-to-install soft starter designed for both small and large motors. It has built-in motor protection, advanced diagnostics, and communication capabilities.
   • PSTB: A more cost-effective solution for smaller motor applications, providing basic starting control and protection.

4. Eaton

   • PowerXL DE1: Eaton’s compact soft starter is ideal for applications where space is limited. It provides smooth motor starts and stops with a wide voltage range and adjustable features.
   • PowerXL DC1: A versatile and rugged soft starter, suitable for a variety of applications including fans, pumps, and compressors.

5. Rockwell Automation (Allen-Bradley)

   • Sirius 3RW30/40/50: These models offer various features for both small and large applications, with the ability to integrate into more complex control systems.

6. GE Industrial

   • AF-300: The GE AF-300 series is known for its robust features, including easy-to-use control for a wide range of motor applications.

7. Toshiba

   • SG2: This is a simple-to-use model for small-to-medium motors, with integrated protection features and easy configuration for most industrial applications.