Variable frequency drive VF control and vector control

At present, the main purpose of using frequency converters is energy saving and speed regulation, so according to different requirements, there are frequency converters with different control functions: conventional V/F control frequency converter and vector control frequency converter.

With conventional V/F control, the voltage drop of the motor will increase relatively with the decrease of the motor speed, which leads to the fact that the motor cannot obtain sufficient torque due to insufficient excitation, especially at low frequencies. That is to say, the conventional V/F control VFD cannot satisfy the output of the rated torque of the motor at low frequency. In addition, in the V/F control, the user presets a u/f curve according to the load condition, and the inverter adjusts its output voltage according to the change of the output frequency when it is working, that is to say, the V/F control It is to make the inverter work according to the pre-arranged compensation level, which cannot be changed with the change of the load. However, V/F control inverters are widely used for their superior cost performance in the occasions where the purpose of energy saving is not high and the speed control accuracy is not high.

The basic principle of vector control frequency converter is to control the excitation current and torque current of the asynchronous motor respectively according to the principle of field orientation by measuring and controlling the stator current vector of the asynchronous motor, so as to achieve the purpose of controlling the torque of the asynchronous motor. Specifically, the stator current vector of the asynchronous motor is decomposed into a current component that generates a magnetic field (excitation current) and a current component that generates torque (torque current) to be controlled separately, and the amplitude and phase between the two components are controlled at the same time, that is, control Stator current vector, so this control method is called vector control method. Since the vector control can make the inverter change the output frequency and voltage in real time according to the frequency and load conditions, its dynamic performance is relatively perfect. The torque can be precisely controlled, the system responds quickly, the speed range is wide, and the acceleration and deceleration performance is good. In occasions with high requirements on torque control, it is appreciated by users for its superior control performance.

Now many new general-purpose inverters also have the vector control function, but they are required to input complete motor parameters when setting parameters. Because the vector control is based on the parameters of the motor, it is particularly important to complete the motor parameters so that the inverter can effectively identify the motor and control the motor well.

We provide various types of variable frequency drive, professional inverter manufacturers, please consult us for more information.