Soft starting is actually stepless reduced pressure starting.When the power supply voltage is changed, the critical torque difference of asynchronous motor is invariable, but the critical torque decreases more.Therefore, when starting at low pressure, the starting torque will be greatly reduced, as shown in figure a.
After realizing variable frequency speed regulation, the mechanical characteristics of the motor will be greatly improved due to various compensation functions and vector control functions of the frequency converter, which can ensure a large starting torque, as shown in figure b.
Frequency converter is used for speed regulation, the output of the frequency converter not only changes the voltage but also can change the frequency.
The soft starter is actually a voltage regulator, which can protect the motor. When the motor is started up, the output of the soft starter only changes the voltage but not the frequency.
Inverter has all the functions of soft starter, but its structure is complex and the price is much more expensive than that of soft starter.
The frequency converter controls the electrical equipment by adjusting the frequency, and can adjust the speed and start, such as the frequency conversion pump used in industry.Soft start is basically away from the circuit by changing the resistance in the series, so that the current from small to large, such a way to start the high-power motor, used to reduce the high-power motor directly start to cause fluctuations to the grid, or cause some trivial load unloading trouble.