三相低频焊机主电路的控制模型与软件流程

论述了三相低频电阻焊机主电路的工作原理及工作过程.通过对控制角α变化时,六只晶闸管的导通及关断过程分析,得到了主电路正常工作时控制角α的可靠移相范围.在此基础上,建立了三相低频焊机电流百分数控制的数学模型及网路电压补偿的数学模型,并论述了主电路控制系统的软件流程.按上述控制模型及控制思路设计的控制系统,配用600 kW的三相低频焊机进行了通电焊接试验.结果表明,当电流百分数为80%时,晶闸管已出现关不断现象,当α小于功率因数角φ时,最后开通的晶闸管将难以关断.

Control model and software flow of main circuit for 3-phase low frequency welder

The working principle and process of the main circuit for 3-phase low frequency welder were discussed.After analyzing the conducting and shutting process of the six silicon-controlled rectifiers (SCR)with changing the pilot angle, the reliable phaseshift range of pilot angle was obtained, within which the main circuit can work steadily.Based on the above studies, the current-percentage-control mathematic model and voltage-compensation mathematic model were set up respectively, and the software flow of control system for main circuit was designed.A control system was made according to the control model and method in this study, and it was tested for controlling a 600 kW 3-phase low frequency welder.The welding experiment showed that, one of the SCRs will not shut normally when the current-percentage is up to 80%, which proved that the last conducted SCR is difficult to shut when the pilot angle is less than the power angle.