Development Of Inverter Type Micro Arc Oxidation Power Supply With Continuously Adjustable Output Parameters

Micro arc oxidation power is one of the most important elements in micro arc oxidation process.Its output characteristics directly affect the surface modification effect of the metal surface.Different voltage output modes have their own advantages,but the commonly used micro arc oxidation power supply is chopper output,and the output form is limited.The PWM inverter can theoretically track the output of any given modulation waveform and achieve multi waveform output.At present,the research of inverter type micro arc oxidation power supply is less.Based on this background,a continuous and adjustable invert type micro arc oxidation power supply is developed,which can output a variety of wavefo rms according to the different process requirements and help to expand the application range of the micro arc oxidation process.It can further optimize and improve the micro arc oxidation technology.Aiming at the requirements of multi waveform output and continuously adjustable output parameters,the implementation scheme of combining fully digital controlled Direct Digital Frequency Synthesis technology with PWM inverter technology is put forward.The method of using DSP to generate PWM pulse waveform under asymmetric rule sampling is studied,and the calculation formula of PWM wave generation based on DDS technology is derived,and a specific method to realize frequency modulation and voltage regulation is given.The phase mutation of the power supply in the large range frequency conversion process is theoretically studied.On the basis of the detailed analysis of the principle and formula of the DDS technology,the mechanism of its production is expounded,and the software realization method for restraining the mutation is given.In view of the existence of zero crossing oscillation in the asymmetric output waveform,the fundamental reason is that the resonant peak of the output filter is caused.In view of this,on the basis of reasonable design of the i nductance capacitance parameters of the output filter,through the analysis and comparison of the transfer function and frequency characteristic of four passive damping methods,the best effective active damping method,inductor current proportional feedba ck control,is selected and deduced,and the structure design of the double closed loop control system is completed.And parameter calculation,and verify the effect of resonant spike suppression by simulation.In view of the high adjustment rate of the output voltage load of the power supply at high frequency,the influence rule of the system parameters is analyzed quantitatively,and the closed loop control strategy of increasing the output voltage is proposed to improve the output voltage load adjustment rate.The structure and parameters of the three loop control system are designed,and the effect of the load adjustment rate of the proposed strategy is verified by MATLAB simulation.On the basis of theoretical analysis and simulation verification,a pow er supply experiment prototype is built.The experimental results verify the feasibility of the proposed scheme and the effectiveness of the control strategy.It shows that the developed inverter type micro arc oxidation power has realized the function of multi waveform output and output parameters continuously adjustable,and meets the requirements of various indexes.It has good practical value.