Name a method used to mitigate motor inrush current at starting.

Name a method used to mitigate motor inrush current at starting.

• A. Star-delta starter only
• B. Soft starter (or star-delta starter); soft starter gradually applies voltage.
• C. Immediately applying full voltage
• D. Increasing the load before starting

Answer: (B)

When a motor starts, it presents a very low impedance and pulls a large inrush current. To keep that surge from stressing the electrical system, you limit how quickly voltage and current are applied during start. A soft starter achieves this by using controlled switches to ramp the supply voltage up gradually, so the motor gains speed smoothly and the peak current stays well below direct-on-line levels. A related method is star-delta starting, which reduces the voltage (and current) during start by wiring the windings in star and then switching to delta for normal operation. The essential idea is to avoid applying full voltage all at once; a soft starter provides the controlled, gradual ramp that most effectively minimizes inrush, making it the best answer.

When a motor starts, it presents a very low impedance and pulls a large inrush current. To keep that surge from stressing the electrical system, you limit how quickly voltage and current are applied during start. A soft starter achieves this by using controlled switches to ramp the supply voltage up gradually, so the motor gains speed smoothly and the peak current stays well below direct-on-line levels. A related method is star-delta starting, which reduces the voltage (and current) during start by wiring the windings in star and then switching to delta for normal operation. The essential idea is to avoid applying full voltage all at once; a soft starter provides the controlled, gradual ramp that most effectively minimizes inrush, making it the best answer.