Research On A New High-Power Air Plasma Cutting Machine

Plasma cutting technology is a set of computer technology, plasma cutting technology, inverter technology in one high-tech, and its development is based on digital control, plasma arc characteristics, power electronics technology and other subjects on the basis of common development. With the power electronics and the rapid development of microelectronics technology, new devices, advanced control technology and the continuous introduction of new technology, cutting technology has been rapid development. High-speed, high efficiency, digital, intelligent modern cutting technology, the main direction of development is the only way to achieve a modern cut. The quality of plasma cutting power has a key role in plasma cutting technology,in this paper, a kind of new high-power air plasma cutting power supplies using a new type of circuit structure, the former part push-pull inverter used to achieve constant voltage source, the latter part using DC chopper to achieve constant current source.This paper analyzes the push-pull inverter and its principle and, combined with practical engineering design requirements, calculation and set the maximum duty cycle of inverter-driven PWM signals of the power switches, but also put forward using PIC16F877A microcomputer output fixed frequency pulse-width of the drive which will replace the PWM control signal modulation module to drive the full-bridge inverter in order to obtain constant voltage source, testing proved that the use of microcontroller PWM wave generated by both accuracy and stability high-level constant voltage source and pre-measured waveforms showing that level constant pressure system is reliable, voltage output stability and precision.The latter part of the control circuit consists of a given circuit, feedback circuit, comparing amplifier circuit, PWM circuit and after-class drive circuit. We get the external characteristic of cutting power by using the chopper, first introduced the characteristics of cutting power outside the classification and formation mechanism, combined with cutting, plasma arc and power to work with the principle of external characteristics of air plasma power to choose the external characteristics of the constant external characteristics of flow. Meanwhile analysis of the circuit parameters affect the cutting current in the current value of a certain given circumstances, by regulating the current feedback depth, can control the size of the actual cutting current. Pre-and post-class all use M57962L as the driver chip of power switch IGBTs. In addition, since cut current is large, this paper also designed to protect the circuit, including the over-current protection and over-temperature protection to ensure that air plasma cutting machine reliability.The results show that the air plasma cutting machine relative to the switch air plasma cutting power supply has the advantages of small Volume, light weight; relative to the full-bridge inverter air plasma cutting machine has the advantages of high reliability and large power.