The Reliability Research On The Digital Power For Mg Alloy Microarc Oxidation

Micro-arc Oxidation is a new method for surface treatment, it also named as micro-plasma oxidation or anodic spark deposition. The surface layer which is formed by this technology has excellent physical-chemical features, such as excellent bonding strength with the substrate, high hardness, wear resistance, corrosion resistance, high thermal shock resistance, good electric insulation layer, higher breakdown voltage. More and more scholars' interesting has been aroused in the field of material surface treatment for the technology of Micro-arc Oxidation. The power source used in this technology is the micro-arc oxidation power.The power source is the key equipment for ceramic membrane which is produced by the technology of micro-arc oxidation. Most power supplies, which is used for disposing the surface of metal in this field, are DC or unipolar pulse at present. The double-pulse WVF Micro-arc Oxidation power based on DSP is designed to eliminate the deficiency of current power supply. This is a high power bipolar power supply, the parameter such as amplitude, frequency, duty ratio and number of positive and negative pulse can be adjusted continuously. The optimum ceramic layer can be obtained through the parameter optimization. As well, the power supply possesses the characteristics of high efficiency, safety, reliability and convenient operation. Therefore, it can meet the desire of experimental study and industrial production.This paper analyzes the reliability of vulnerable part in main circuit of micro-arc oxidation equipment which is worked in specific circumstance of high voltage and high current, and the solution is also proposed. The parameter in micro-arc oxidation equipment such as the pulse output frequency and duty ratio is dominated by IGBT. Therefore, the reliability of this is decided on IGBT. The deeply analysis and comparison of circuit structure, working principle and service performance has been carried out for the common IGBT drive circuit which include M57959, EXB841, 2SD315. Through the experiment, it has been discovered that the driven power in the first two circuits were not enough, the IGBT was easy to be damaged and not in the state of completely turn-on, the switching loss was high. 2SD315 is suitable for high-power micro-arc oxidation equipment drives, because it has great peak output current, strong driving ability and high isolating voltage capability.Over-voltage and over-current were occurred during the process of turn-on and turn-off with IGBT. In order to worked safely, the structure and failure mechanism of IGBT has been analyzed, various guarding method were proposed towards the over-voltage, over-current and overheating, etc.Micro-arc oxidation process is relatively complex, and the different power modes of the micro-arc oxidation have greater impact on the performance of the micro-arc oxidation film. The experiment has been carried out in different power mode, the technique was researched deeply, and the reference was given for future large-scale industrial surface treatment of micro-arc oxidation.