With the rapid development of the domestic frequency converter industry, the price of frequency converters is no longer prohibitively high. They not only solve the problem of large inrush current generated when starting electrical appliances, but also have a good energy-saving effect. Therefore, the once-popular soft starter seems to have declined, and its noise level is getting lower and lower.
Introduction to Soft Starters
Soft starters were first proposed in the 1970s and 80s, then called thyristor phase-shifting starters. Over forty years of development, the cost of soft starters has continuously decreased. As the product quality of many domestic companies became very stable, soft starters gradually replaced direct starters, autotransformers, and star-delta starters. Modern soft starters have evolved into motor control equipment integrating soft starting, soft stopping, light-load energy saving, and multi-functional protection. They can achieve a smooth, shock-free motor start throughout the entire process, and various parameters during the starting process, such as current limiting values and starting time, can be adjusted according to the characteristics of the motor. Soft starters effectively solve the problems of motor starting impact on the power grid and the operation of bypass contactors after starting. They also have multiple motor protection functions, therefore, soft starters are widely used in the market.
Inverter Introduction
A frequency converter (VFD) is a power control device that uses frequency conversion technology and microelectronics to control an AC motor by changing the frequency of the power supply. A VFD typically consists of four parts: a rectifier unit, a high-capacity capacitor, an inverter, and a controller. The VFD adjusts the voltage and frequency of the output power supply by switching its internal IGBTs, providing the required power voltage according to the actual needs of the motor, thereby achieving energy saving and speed regulation. In addition, VFDs have many protection functions, such as overcurrent, overvoltage, and overload protection. With the continuous improvement of industrial automation, VFDs have been widely used.
Advantages of frequency converters
In terms of application, soft starters and frequency converters are two completely different products. A soft starter is essentially a device that controls voltage and limits starting current, used for starting motors, changing only the amplitude of the output voltage without altering the frequency; while a frequency converter is used where speed regulation is required, changing both the voltage and frequency of its output. Functionally, a frequency converter possesses all the functions of a soft starter; therefore, it can be said that a frequency converter is a more powerful type of soft starter.
While soft starters solve the problem of motor starting, they do not offer significant energy savings. In recent years, with the rapid rise of domestic production of frequency converters in my country, their quality and stability have improved rapidly. Coupled with advantages in service and cost, the cost-effectiveness of frequency converters has continuously improved, making their competitive advantage in quality and price increasingly apparent. Soft starters not only solve the problem of large inrush currents generated during motor starting but also have excellent energy-saving effects and frequency conversion capabilities. Therefore, soft starters face increasing pressure to be replaced.
Currently, soft starters are only used in a small number of operating conditions, such as when the motor load exceeds 90%. For other operating conditions, while soft starting was previously used, frequency converters are now more commonly employed due to their energy-saving effect of approximately 30%. Furthermore, the price of frequency converters has decreased significantly. Today, frequency converters are widely used in industrial and mining enterprises, covering almost all fields. It's no exaggeration to say that wherever electric motors are used, frequency converters are almost certainly present.
Inverter performance testing
Inverter performance testing primarily involves electrical parameter efficiency testing, control performance testing, and protection performance testing. Electrical parameter efficiency testing mainly focuses on voltage, current, input/output power, frequency, power factor, and efficiency; control performance testing mainly focuses on speed accuracy, torque accuracy, and control response; protection performance testing mainly focuses on undervoltage protection, overcurrent protection, and overload testing. Zhiyuan Electronics' MPT1000 motor testing platform offers a complete solution for inverter performance testing, enabling comprehensive evaluation of inverter performance. A typical measurement scheme is shown in the figure below.
The Future of Frequency Converters
According to experts, the soft starter market will continue to grow steadily in the coming years, but at a much slower pace than the frequency converter market. As market competition intensifies, smaller, less competitive companies will be eliminated, further increasing market concentration. With the rapid development of frequency converters, their market share will continue to grow. Whether soft starters will completely disappear in the future remains to be seen and requires further market validation.
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