Development Of DC Inverter Electrofusion Welding Machine Based On Power Factor Compensation

Polyethylene(PE)pipe has the advantages of corrosion resistance and long service life,and has been widely used in nuclear power,gas transmission,urban water supply,chemical industry,post and telecommunications and other fields.In the engineering application of polyethylene pipe,the key to affecting the quality and structural integrity of pipe network is the pipe connection technology,among which electrofusion welding is a widely used pipe connection method at home and abroad.In order to adapt to the development of polyethylene pipe welding technology in China,it is of great practical significance to further carry out the research on electrofusion welding technology and welding equipment according to the existing theoretical and practical research results.At present,there are mainly two types of electrofusion welding machine on the market: AC phase control type and DC inverter type.In the actual engineering construction,the differences in circuit principle and voltage regulation technology between the two types of welding machine are not distinguished,and there is a problem of mixed use of AC welding machine and DC welding machine.However,since the electrofusion pipe fittings are inductive loads,when the AC welding machine and DC welding machine are welded according to the same welding process parameters,the power factor of the AC phase controlled electrofusion welding machine is less than 1,resulting in the inconsistent energy input to the electrofusion pipe fittings and the inconsistent welding effect of the obtained electrofusion joints.This research is supported by the "Eagle Plan" project funding(grant number:CY2022002)and the first batch of key research and development programmes in Shandong Province(major science and technology innovation project)project funding(project number: 2021CXGC010303).Aiming at this problem in welding construction,this paper conducts a quantitative study on the output power factor of AC phase controlled electrofusion welding machine.Based on the results of power factor research,a DC inverter electrofusion welding machine with power automatic compensation function is designed.The main research work is as follows:(1)The power compensation strategy of DC inverter welding machine based on power factor is proposed.Aiming at the process of electrofusion welding of AC phase controlled electric welding machine,the theoretical calculation of output power factor and numerical fitting of the calculated results are carried out,and the experimental verification is completed.According to the electrical parameters required by theoretical calculation,the measurement scheme of resistance and inductance is designed,and the power compensation strategy suitable for DC inverter electrofusion welding machine is proposed.Through this power compensation strategy,the consistency of welding effect of AC welding machine and DC welding machine is ensured.(2)A DC inverter electrofusion welding machine system is built.Based on the designed power compensation strategy,the system requirement analysis and system hardware architecture design of DC inverter electrofusion welding machine are completed.Under the requirements of technical parameters and functional of the welding machine,the circuit principle design,the selection of related components,the design of the PCB board drawing,the production and debugging of the physical circuit board,etc.are completed respectively.Finally,the DC inverter electrofusion welding machine which can independently measure the power factor and realize power compensation is successfully built.(3)The application and verification of power compensation strategy are realized.After completing the construction of the welding machine,the basic output function of is tested first.After determining that the basic functions of the welding machine meet the system design requirements,the welding experiment is carried out by using the power compensation strategy.The welding effect is verified and analyzed from three angles: temperature field simulation,joint ultrasonic testing and tensile stripping experiment.The results show that the power compensation strategy of DC inverter electrofusion welding machine can effectively ensure the consistency between its welding effect and that of AC phase controlled electrofusion welding machine,and can improve the welding quality of electrofusion joint.