Variable frequency power supply is the general name in domestic, more accurately, it should be called AC power frequency converter, generally abbreviated as AFC. The whole development history of variable frequency power supply basically develops with the development of electronic device. 

Before and after the 1980s, the electronic variable frequency power supply was mainly based on the small instrument power supply of Japan. The instrument power supply was mostly made by the way of crystal amplification. After the 1980s, it was introduced into Mainland China through Taiwan. The characteristics of power of this period were: small power, good precision and low efficiency.

In the 1980s, Mainland China embarked on the road of reform and opening up. At this stage, the import and export equipment of Mainland China gradually increased, especially the export share of appliance represented by microwave oven and air conditioning increased, so the high power variable frequency power supply was required to be tested. The original product power could not meet the demand for this part of market application, so the power suppliers sought for new technology to expand the power of the power supply. According to the technical conditions and electronic devices at that time, it mainly developed in two aspects. One was to maintain the crystal style, and use multi-machine parallel for capacity expansion; The other way was to use the power crystal module.

The crystal multistage series method needs to solve the circulation problem, and it is inefficient and consumes too much in the industrial production process; Power crystal module frequency conversion method reacts slowly and the power is limited, the operating voltage is low, it can withstand voltage of about 600V. The output adopts PAM filtering method (single square wave plus low filter), and the output waveform distortion is large. The power supply products produced by the two methods still could not meet the growing demand, so when the high-power load needed to be tested in frequency conversion, the motor + generator method (M+G) was generally used to meet the requirements.

In the use of the motor + generator method (M+G), there were problems of wear and efficiency conversion. Later, with reference to the United States technology, SCR was used to make the inverter. The power supply in such a way had large power, which could satisfy the customer’s needs, and it’s a good way to replace the motor + generator method (M+G). But the series of products had a major drawback, in the process of transformation, the noise of the machine was very large, up to 70dB<1m

With the development of semiconductor technology, at the end of the 1980s, Fuji produced the first generation of IGBT. The characteristics of the electronic device were that it integrates the advantages of GTR and MOSFET, the switching speed was fast, the flow capacity was strong, so it was soon applied to the field of inverter. With the powerful Mitsubishi, Semikron, Infineon and other manufacturers joining the IGBT field, the development speed of IGBT changed rapidly, the speed of upgrading was accelerated, and the switching speed and flow capacity of IGBT were further strengthened. Thus the production of high-power variable frequency power supply can be realized.