Research On 150kHz Induction Welding Power With High Power Factor

Series resonant induction welding power has made great progress in our country, but there is still large disparity comparing with foreign countries. Especially in high power and high frequency fields, we have significant diaparity with Western Europe and Japan. At present, the direction of welding power and the problems faced by research include improving the operating frequency of power converter, problems caused by high frequency switching devices and loss improve problem of passive devices, Harmonic pollution and loss issues on the power grids caused by induction welding power, the application of digital control.The input current and waveform distortion is due to the rectifying part, because it usually adopts the thyristor phase-controlled rectifying or diode rectifying in the AC/DC link.It will not only seriously interfere with the power line voltage, but also reduce the energy efficiency, which means the energy wastage is increased.Power Factor Correction technology has been applied to this paper. For the negative impact on the grid, we try to add an improved soft boost circuit-lossless snubber circuit between the rectifier and the inverter, which is used to replace the traditional LC filter to achieve power factor correction.Thereby it reduced the boost circuit switching loss at high frequency and improved the correction circuit application. TMS320LF2407A was used to achieve power factor correction with the average current mode control. We compared several power regulation method, and finally chose the phase shifted pulse width modulation as power regulating methods on the AC side.For the current situation of IGBT's low frequency, we chose a new inverter—through IGBT parallel to achieve multiplier work.In the end of the study, we researched the digital control system of induction welding power, which is mainly constituted by the integrated PLL chip 74HC4046, DSP (digital signal processor) and CPLD (compelx programmable logic device) component.The DSP calculated the difference between actual power and rated power of the load, then got phase shift angle.CPLD received signal of phase shift angle and phase-lock, which is used to accomplish the phase-shifted PWM control. In addition, we also designed the external circuit of the control system, such as over-voltage, over current protection circuit and IGBT driving circuit based on chip IXDN404. After analysis of soft boost circuir and multi-frequency inverter, we made MATLAB simulation on the main circuit, as the basis for subsequent experiments. Experimental results and simulation results are consistent, it confirmed that power factor corrections applied to the induction welding power in the technical is reasonable and feasible.