Soft starter startup method - Solutions - Huaqiang Electronic Network

Photocoupler

1. Direct On Line (DOL) Starting – This is the simplest and most common method of starting an electric motor. In this mode, the motor is directly connected to the power supply, which results in a high inrush current and torque at startup. While it’s cost-effective and easy to implement, it may not be suitable for large motors due to the stress on the electrical system.

Direct starting current and torque

2. Star-Delta (Y/Δ) Starting – This method is commonly used for three-phase induction motors. Initially, the motor is connected in a star configuration, reducing the starting voltage and current. Once the motor reaches a certain speed, it is switched to a delta connection for full-speed operation. This technique helps reduce the initial current surge, making it ideal for larger motors.

Squirrel cage motor star-delta start

3. Autotransformer or Tap Transformer Starting – This method uses an autotransformer to reduce the voltage supplied to the motor during the starting phase. The transformer has multiple taps that allow for different voltage levels, giving more control over the starting process. It’s particularly useful when a smooth and controlled start is required, especially for heavy-duty applications.

Tap transformer start

4. Soft Starter – A soft starter is an electronic device designed to gradually increase the voltage applied to the motor, allowing for a smooth and controlled start. This reduces mechanical stress on the motor and connected machinery, as well as minimizes electrical disturbances in the power system. Soft starters are widely used in industrial and commercial applications where a gradual start is necessary.

Soft starter to start