With the rapid development of modern electric power and electronic technology and the microelectronic technology, variable frequency speed regulating device continue to mature, its application scope is more and more widely levees are, at this moment,, reasonably use energy (especially power) has become possible. 10 resources VVVF is also the national focus on organizing the implementation of conservation and comprehensive utilization of technology demonstration. It is the power frequency (50HZ or 60H) transform into a variety of frequency AC power, to realize the motor speed operation of the equipment. The rectifier circuit will be converted into AC DC, DC intermediate circuit of the rectifier output smoothing filter, inverter circuit to DC and then reverse into the AC voltage and frequency control. Frequency and dry type rectifier transformer as isolated power supply device, is an important part of. According to the market demand, our company has developed a dry type rectifier transformer for frequency control using the mature technology. It is a kind of special for medium and high voltage inverter to provide a number of rectifier power supply device, using the Yanbian triangle principle, for the power unit to provide different phase AC power supply, reduce the harmonic content, improve the quality of power supply.