Abstract:

In order to enhance the arc controllability during the MAO (Micro- Arc Oxidation) process,a high- fre-quency narrow- pulse inverter power supply for micro- arc oxidation is designed in the perspective of pulse energycontrol.This power supply adds an impedance matching circuit to the main circuit of the source on the basis of a tra-ditional two- stage inverter structure.Thus,rapidly releasing and storing of energy in the circuit and load is realizedunder the variable polarity mode.Then,a cooperative control strategy is presented to carry out DC/pulsed/ variablepolarity pulsed modes,and the corresponding operation patterns for the main circuit are also described.Finally,theload characteristic of the proposed power supply is analyzed and the availability of the equivalent model of the loadcharacteristic is verified by comparing simulation and experimental waveforms.Experimental results demonstrate that,for the proposed power supply,both increasing the pulse frequency (up to 20kHz) and decreasing the pulse width(low to 20μs) help to realize the precise control of pulse energy and enhance the energy utilization of the system,andboth the porosity and surface roughness of the coating obtained in the high- frequency narrow- pulse mode are lower.

Key words: microarc oxidation, power supply, inverters, load characteristic, high frequency narrow pulse, coopera-tive control strategy