Frequency converters and soft starters are both devices used for motor control, but they have significant differences in their roles, functions, and application scenarios.

Function: The primary function of the frequency converter is to adjust the motor's speed by changing the power supply frequency and voltage. This enables stepless speed regulation of the motor. On the other hand, the main role of a soft starter is to limit the starting current by gradually increasing voltage during motor startup. This helps avoid large current impacts and thermal effects, thereby extending the motor's service life.

Additional Functions: In addition to speed regulation, frequency converters also provide various protection functions such as overload protection, overvoltage protection, undervoltage protection, overcurrent protection, input phase protection, output phase protection, and three-phase unbalanced protection. They also offer multiple control functions like linear acceleration and deceleration, S-curve acceleration and deceleration modes as well as time setting options. Conversely,the soft starter primarily focuses on providing smooth start-up and stoppage capabilities for motors while offering features like phase loss protection，overload protection，overvoltage/undervoltage protections etc.

Application Scenarios: Frequency converters are suitable for applications where frequent adjustment of motor speed is required such as fans or pump loads. Soft starters find their suitability in situations where motors need smooth start-ups/stoppages like compressors or centrifugal pumps.

In summary,frequency converters and soft starters play distinct roles in motor control with specific application scenarios requiring appropriate equipment selection based on individual needs.Furthermore,differences exist between them not only in terms of functionality but also price considerations.