【導(dǎo)讀】畢業(yè)設(shè)計(jì)(論文). 課題60KVA智能中頻焊接電源設(shè)計(jì)。本文分析了當(dāng)今中頻電阻焊電源的國內(nèi)外研究現(xiàn)狀以及未來產(chǎn)品的發(fā)展趨。勢(shì)，介紹了中頻逆變電阻焊接電源的關(guān)鍵技術(shù)以及存在的問題，描述了中頻逆變。本文針對(duì)這種低壓大電流焊接電源所具有的特點(diǎn)，完成了對(duì)中頻逆變電阻焊。出了各個(gè)器件的具體參數(shù)。為了保證了系統(tǒng)的可靠工作，對(duì)中頻電阻焊機(jī)的主電路采取了抗干擾與可靠性設(shè)。Matlab/Simulink軟件對(duì)主電路建立了仿真模型，在完成仿真之后，對(duì)仿真出來

　　

【正文】 The difference in the physical properties and dimensions between the bridge band and column is signi?cant. This makes the temperature distribution of the welding zone very uneven. The high temperature zone is close to the side of the column, but does not lie on the nter face of the band and the column. Experiments have demonstrated that the bridgeband spotwelding process is highly sensitive to the welding current waveform, but the current waveform control ability of the condensertype spotwelder is very limited and cannot meet the welding quality requirements. There is also a clear splash in the welding process that is absolutely not allowable. Therefore, a new kind of spotwelding power source in which the output current waveform can be adjusted arbitrarily and precisely has been developed ?rst. Controlled by a 8098 singlechip microputer, the Mosfet precise spotwelding power source can deliver output 安徽建筑大學(xué) 畢業(yè)設(shè)計(jì)（論文） 32 currents with an arbitrary wave form. The current waveform adjustment range is 0–600 A and 0– ms, the adjustment precision being A for the current and ms for the time. The power source can deliver not only three pulse current waveforms, which include a preheating, welding and tempering pulse in turn, but also any special and plex current waveform, by accurate control of the current instantaneous value. This makes welding possible by using the optimum current waveform. This new kind of spotwelder can meet entirely the strict requirements of bridgeband spotwelding. An industrial PC has also been used to monitor and manage the welding process and the various parameters, which will further improve the behaviour of the spotwelder. 2. Main circuit design of the power source The main circuit structure is shown in Fig. 1. A parallel power Mosfet group is used to adjust the current wave form. The Mosfet is designed to work in a linear state, so the instantaneous value of output current waveform can be controlled precisely. Mosfet is a kind of voltagecontrolled ponent and is easy for parallel use, which simpli?es the circuit greatly. There are no secondary breakdown problems with Mosfet, which makes the power source more reliable. The chief defect in using Mosfet in a linear state is that the power loss is higher than that in the on–off state, but both the absolute value of the output current and the duty cycle of this power source are very low, and so the power loss is not very high. KT and KV sensors are used to sample the welding current and voltage. The program ?ow chart of the singlechip micro puteris shown in Fig. In addition to presetting and controlling the welding current waveform arbitrarily and precisely, they stem can also carry out a selfcheck and give an alarm when some Mosfet are damaged。 the difference between the practical and preset current is over the limit。 the welded join tresistance value is over the limit。 or the error of data munication between the 8098 and the IPC is serious. The welding program in the chart includes realtime control of the welding current waveform according to the preset parameters, sampling the welding current and voltage and displaying the welding current waveform and the welded joint 安徽建筑大學(xué) 畢業(yè)設(shè)計(jì)（論文） 33 resistance value. 3. Principle of the microputer control system The microputer control system shown in Fig. 2 consists of a 8098 singlechip microputer, an industrial PC (IPC) and an interface circuit. . Microputers and their interface circuit The 8098 singlechip microputer is the realtime control core of the system. A pulsewidth modulation (PWM) signal delivered by the 8098 is converted into an analog signal Ug through U1 and U2 employed as a D/A converter. The output current waveform is established according to Ug acting as the given signal. Thus, the output current waveform can be controlled arbitrarily by the microputer. Two A/D converter paths CH4 and CH5 of the 8098 are used as sampling input ports of the welding current and voltage in the feedback control system. The IPC is used for monitoring and managing the system. The full twoway serial port MAX232 is used for serial munication between the 8098 and the IPC. The 8098 can not only receive data from the IPC but also transmit data to the IPC through MAX232. The 8098 links up with the IPC by a plugin munication wire only. This design makes it possible for the 8098 to also do the work of presetting and controlling the output current waveform independently out of the monitoring of the IPC. Thus the IPC is an optional device in the system. . Man–machine conversation interface The parameters for presetting the welding current wave form can be inputted into the system from the keyboard of the IPC by an operator, the curve of presetted waveform being displayed on the monitor of the IPC. Then the parameters will be transmitted to the 8098. The practical output current waveform is controlled by the 8098 singlechip microputer in realtime. At the end of every spot welding process, the 8098 will transmit sampled parameters of practical current values and welded joint resistance values to the IPC. The IPC will then store the data in the disk, draw the curve of the practical current waveform and display the resistance value as a reference for estimating the welded joint quality in the monitor. The optimum welding conditions of various welding work pieces can be stored in the IPC and transferred to the 8098whenever needed. Various data, curves and documents of the product are stored and can be printed for inquiry and analysis. The system gives an alarm when errors occur in the welding process and also displays the types of errors。 that makes the operation visual and very easy. The singlechip microputer can also do the work independen