The Working Principle of AC Frequency Converters: Variable frequency technology is a method that adjusts the speed of an AC asynchronous motor by altering the power frequency through a frequency converter. This is achieved by first converting AC to DC via the frequency converter, and then converting the DC back to AC to control the speed of the AC motor.

The automatic protection device project for the series of winding machines controls the inverter through adjusting the analog voltage input to the inverter, thereby controlling the frequency of the output power supply, making the speed of the AC motor follow the changes in the output power supply frequency.

The speed of a three-phase asynchronous motor is determined by the point frequency, the number of poles of the motor, and the slip rate. The torque of an asynchronous motor is produced by the interaction between the magnetic flux of the motor and the current flowing through the rotor. At a constant frequency, if the voltage remains constant but the frequency is reduced, the magnetic flux becomes excessive, the magnetic circuit becomes saturated, and in severe cases, the motor can be damaged.

Therefore, the frequency and voltage must be altered proportionally; that is, while changing the frequency, the output voltage of the inverter is controlled to maintain a constant magnetic flux in the motor, thus preventing the occurrence of weak magnetism and magnetic saturation. As general-purpose inverters typically use V/f control, which is a variable voltage and frequency method for speed regulation, changing the frequency and voltage is a method for motor control.

The company has chosen the variable frequency speed control method, which adjusts the synchronous speed of the motor by altering the frequency of the stator power supply. Its features:

High efficiency; no additional losses during the speed regulation process.

Widely applicable, suitable for cage-type asynchronous motors.

Wide speed range, high hardness, and high precision.