3‑Phase AC Motor Soft Start

Traditionally, 3-phase AC motors are started in a star configuration and then switched to a delta configuration to reduce inrush current and mechanical stress, thereby extending motor life. However, this method requires additional wiring and complex switching mechanisms. An alternative is the phase-cut technique on two phases, which soft-starts (and optionally soft-stops) the motor by reducing the phase cut from 360° to 0°. Relays are used to bypass the Triacs/Thyristors in run mode, eliminating losses and improving efficiency.

System Benefits:

• Simplifies wiring and reduces motor costs by eliminating the need for star-delta connections
• Extends motor life by reducing mechanical stress
• Significantly decreases inrush current and allows precise control over its duration
• Enables easy parameter adjustment using simple potentiometers
• Offers optional bus interfaces for control, such as RS-485 or CAN
• Provides an optional user-friendly GUI accessible via Bluetooth on a smartphone