Soft starters entered the market in the late 1970s and early 1980s, bridging the gap between star-delta starters and frequency converters in terms of functionality, practicality, and price. Using a soft starter allows for control of the motor voltage, gradually increasing it during startup and naturally controlling the starting current. This means the motor can start smoothly, minimizing mechanical and electrical stress. Therefore, soft starters have gained widespread use in the market, and their soft-stop function effectively avoids the "water hammer effect" that occurs when a water pump stops.
Asynchronous motors are widely used in various industries due to their excellent performance and maintenance-free operation. However, they generate a large inrush current during startup (typically 5-8 times the rated current), and the high starting stress reduces the lifespan of the load equipment. National regulations have long stipulated that the grid voltage during motor startup must not exceed 15%. Previous solutions involved increasing the power distribution capacity and using starting devices to limit the motor's starting current. However, increasing the power distribution capacity solely for starting the motor is economically impractical. Therefore, starting devices to limit the motor's starting current are often used, such as Y/Δ converters, autotransformers, and magnetic control. While these methods provide some current limiting, they do not fundamentally solve the problem.
With the increasing demands for automation in drive control, intelligent motor starting devices—soft starters—which use thyristors as the main components and microcontrollers as the control core, are finding wider application across various industries. Soft starters are highly adaptable due to their superior performance, small size, light weight, intelligent control, multiple protection functions, and adjustable starting parameters to suit different loads. Therefore, electronic soft starters will inevitably replace outdated traditional reduced-voltage starting devices such as Y/Δ, autotransformer, and magnetic control starters.
In addition, soft starters have a variety of motor protection functions, which fundamentally solves many of the drawbacks of traditional reduced-voltage starting equipment.
Due to China's relatively backward industrial technology, the frequency converter industry was just starting out more than a decade ago. Lacking pricing power, the domestic market was largely dominated by international brands, resulting in persistently high costs for frequency converters. At that time, domestic squirrel-cage induction motors generally used direct starting, or autotransformers and star-delta starters.
In the 1990s, intelligent motor soft starters with microcontrollers as the core and semiconductor thyristors as the actuators entered the Chinese market. Soft starters mainly solve the problems of the impact on the power grid when the motor starts and the operation of the bypass contactor after starting. They have a good protection effect on the motor and can achieve a certain degree of energy saving (about 5%) under light load conditions.
Although the energy-saving effect of soft starters is far inferior to that of frequency converters, the price of soft starters of the same power is much lower than that of frequency converters. Therefore, soft starters have been widely used in some situations where speed change is not required, and their development accelerated after 2000. Currently, the market size is about 2 billion yuan. Through nearly 20 years of accumulation, the stock of soft starters in my country is huge.
Soft starters are widely used in various industries, with a huge market presence, and their price advantage compared to frequency converters will persist for some time. Therefore, understanding how to use and maintain soft starters is crucial for electrical and automation engineers.
Evita invited variable frequency drive expert Geng Ge to give a detailed explanation of the functions, applications, and maintenance experience of soft starters, using the Schneider ATS48 series soft starter as an example. We believe that through this course, engineers can quickly master the application and maintenance of the ATS48 series soft starter and achieve the effect of applying what they've learned to other situations.
With the rapid development of the domestic frequency converter industry, the price of frequency converters is no longer prohibitively high. Frequency converters not only solve the problem of large inrush currents during motor startup but also offer excellent energy-saving performance. Therefore, the once-popular soft starter seems to have fallen out of favor, becoming increasingly obscure. The pressure to replace soft starters is indeed growing, especially in China.
With the rise of China's frequency converter industry, which has led to a significant drop in the price of frequency converters, frequency converters have gradually replaced soft starters in recent years.
Soft starters were developed to bridge the gap between star-delta starters and frequency converters in terms of functionality, practicality, and price; therefore, they can be considered a transitional product. As the cost of frequency converters gradually decreases, the market space for soft starters will shrink. Whether soft starters will completely disappear in the future remains to be seen and requires further market validation.
Currently, soft starters still have a place in the market. When the motor's operating load power is above 80%, using a soft starter remains the best, most practical, and most cost-effective option. In the next few years, the soft starter market will continue to grow steadily, but at a much slower pace than the frequency converter market. As market competition intensifies, a number of small, less competitive companies will be eliminated, further increasing market concentration. Soft starter applications are currently concentrated in several sectors of China's national economy, with seven major industries: power, metallurgy, building materials, machine tools, petrochemicals and chemicals, municipal engineering, and coal.
