The mMedium Voltage Soft Starter Panel is a device used for starting high voltage AC motors. It consists of multiple sets of high voltage and high power thyristors connected in series and parallel. By controlling the trigger angle of the thyristors, the output voltage can be controlled to meet the different voltage and current requirements during the motor starting process.

During motor starting, a medium- and high-voltage solid-state soft starter increases the motor’s terminal voltage according to a pre-set starting curve, ensuring a smooth start and minimizing mechanical impact on the power grid and connected equipment. Once the motor reaches full speed, the bypass contactor or circuit breaker engages, completing the motor start. While the motor is running, the soft starter continues to monitor the motor, measuring its current and voltage in real time and providing various protections.

Medium voltage soft starter panel are suitable for soft starting large and medium-sized AC motors with rated voltages of 2-15 kV. They are widely used in large-scale steel, petroleum, chemical, aluminum, fire protection, mining, sewage treatment, power generation, highways, and tunnels. They are ideally suited for use with motor-driven equipment such as pumps, fans, compressors, crushers, mixers, belt conveyors, mills, and other electromechanical equipment.

Working principle

The core principle of a mv soft starter panel is based on power electronics technology. It regulates the voltage applied to the motor by controlling the conduction angle of the thyristors. During the initial startup phase, the soft starter outputs a low voltage, then gradually increases it to smoothly accelerate the motor and avoid the high current surge that occurs during a direct start. This voltage regulation method, similar to a ramp, is often referred to as “ramp start.” The soft starter also offers a constant current starting mode, maintaining a constant current during the startup process to further optimize starting performance. In this way, the soft starter effectively reduces the starting current (typically limiting it to 2-4 times the rated current), minimizing grid voltage fluctuations and stress on mechanical equipment.

Control strategies and algorithms

A variety of control strategies are used to adapt to different application scenarios. Common control algorithms include voltage ramp control, current limit control, and torque control. Voltage ramp control is the most basic method, achieving a smooth start by linearly increasing the voltage. Current limit control focuses on maintaining the starting current within a set value to avoid overcurrent. Torque control optimizes motor torque output by adjusting the voltage and is suitable for heavy-load starting. These algorithms are typically implemented in the control unit’s software, allowing users to set parameters such as start time, initial voltage, and current limit through a user interface. Advanced soft starters may also integrate adaptive functions to automatically adjust parameters based on load changes to improve performance.

Future development trends

With technological advancements, medium-voltage soft starters are becoming increasingly intelligent and efficient. In the future, they may integrate more IoT features, enabling remote monitoring and predictive maintenance, further enhancing the user experience. New materials and optimized designs will reduce equipment size and energy consumption, making them more environmentally friendly. As a crucial component of industrial automation, soft starters will continue to play a key role in motor control.