Tips of Frequency conversion Technology（2）

What is the difference between voltage-source inverter and current-source inverter?

The main circuit of the converter can be divided into two types: the voltage-source inverter converts the DC of the voltage source into the AC, and the filter of the DC loop is the capacitor. Current-source cnverter converts that converts the current source from DC to AC, and its DC loop filter is inductor.

Why does the voltage and current of the converter change in proportion?

The torque of asynchronous motor is caused by the interaction between the flux of the motor and the overcurrent of the rotor. At rated frequency, if the voltage is fixed and only the frequency is reduced, the flux is too large and the magnetic loop is saturated. When it's serious, it burns down the motor. Therefore, the frequency and voltage should be changed proportionally, that is, to change the frequency while controlling the output voltage of the inverter, so that the magnetic flux of the motor will remain certain, and the phenomenon of weak magnetic field and magnetic saturation will be avoided. This kind of control method is mostly used in the energy  saving inverter such as fan, pump and so on.